Encyclopedia of Islands

Encyclopedia of Islands

ROSEMARY G. GILLESPIE
DAVID A. CLAGUE
Copyright Date: 2009
Edition: 1
Pages: 1111
https://www.jstor.org/stable/10.1525/j.ctt1pn90r
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  • Book Info
    Encyclopedia of Islands
    Book Description:

    Islands have captured the imagination of scientists and the public for centuries-unique and rare environments, their isolation makes them natural laboratories for ecology and evolution. This authoritative, alphabetically arranged reference, featuring more than 200 succinct articles by leading scientists from around the world, provides broad coverage of all the island sciences. But what exactly is an island? The volume editors define it here as any discrete habitat isolated from other habitats by inhospitable surroundings. TheEncyclopedia of Islandsexamines many such insular settings-oceanic and continental islands as well as places such as caves, mountaintops, and whale falls at the bottom of the ocean. This essential, one-stop resource, extensively illustrated with color photographs, clear maps, and graphics will introduce island science to a wide audience and spur further research on some of the planet's most fascinating habitats.

    eISBN: 978-0-520-94372-8
    Subjects: Ecology & Evolutionary Biology

Table of Contents

  1. Front Matter
    (pp. i-iv)
  2. Table of Contents
    (pp. v-x)
  3. CONTENTS BY SUBJECT AREA
    (pp. xi-xiv)
  4. CONTRIBUTORS
    (pp. xv-xxviii)
  5. GUIDE TO THE ENCYCLOPEDIA
    (pp. xxix-xxx)
  6. PREFACE
    (pp. xxxi-xxxii)
    Rosemary G. Gillespie and David A. Clague
  7. ADAPTIVE RADIATION
    (pp. 1-8)
    ROSEMARY G. GILLESPIE

    Adaptive radiation is one of the most important outcomes of the process of evolution, and islands are places where it is best observed. The term itself was first used by H. F. Osborn in 1902 in describing parallel adaptations and convergence of species groups on different land masses. Since then, adaptive radiation has been widely recognized and defined in multiple ways to emphasize the contribution of key features thought to underlie the phenomenon, including adaptive change, speciation within a monophyletic lineage, and time. Dolph Schluter, a prominent researcher in the field, defines it as “the evolution of ecological diversity within...

  8. ANAGENESIS
    (pp. 8-10)
    TOD F. STUESSY

    Anagenesis is a process of gradual speciation whereby only single endemic species within respective genera diverge within oceanic islands (Fig. 1). In this case, the founding immigrant population does not dramatically and rapidly change and split (cladogenesis) into two or more different species after arrival, which is what happens during the better-known pattern of adaptive radiation.

    The process of speciation through anagenesis is very different from that via cladogenesis (resulting in adaptive radiation). During anagenesis an immigrant population establishes in a suitable new oceanic island habitat. In the absence of ecological opportunity, such as may occur on an island with...

  9. ANTARCTIC ISLANDS, BIOLOGY
    (pp. 10-17)
    STEVEN L. CHOWN and JENNIFER E. LEE

    Antarctic islands vary substantially, from small exposed mountain peaks and large dry valleys surrounded by ice to the highly variable Southern Ocean islands, which have a considerable range of sizes and geological histories. Reflecting the diverse locations and origins of Antarctic islands, their biota varies substantially. Some ice-free areas of the continent are devoid of anything except microbial life, while others support bryophytes, lichens, nematodes, arthropods, and, occasionally, breeding seabirds. The Southern Ocean islands range from those virtually covered by glaciers to others that have lush, vegetated landscapes at their lower elevations, riddled by the burrows of breeding seabirds and...

  10. ANTARCTIC ISLANDS, GEOLOGY
    (pp. 17-20)
    JOHN L. SMELLIE

    Islands in the Antarctic region (south of 60° S) have an importance beyond a simple curiosity related to their current geographical and climatic isolation. They contain a repository of geology that is representative of much of the geology of Antarctica; they are typically more accessible and often better exposed than elsewhere in Antarctica as a result of recent marine-related stripping of superimposed snow and ice; and some islands may also have acted as persistent ice-free refugia for fugitive plant and animal communities at the end of each interglacial, when the continent itself was swathed in extensive ice sheets. The survival...

  11. ANTILLES, BIOLOGY
    (pp. 20-29)
    CHARLES A. WOODS and FLORENCE E. SERGILE

    The “Antilles” is an archipelago of over 7000 large and small islands, cays, reefs, and exposed offshore banks with long and diverse geological and biological histories. The total human population of the Antilles is 34.5 million. The heterogeneous assemblage of islands stretches in an arc over 3200 km long. The islands originated in a variety of ways (volcanism, uplifted island arcs, exposed and uplifted coral banks, movements of major plates, changes in sea levels) and have had a history of numerous vicariance (separation) events, as pieces of islands as well as whole islands became attached and unattached, submerged and reemerged....

  12. ANTILLES, GEOLOGY
    (pp. 29-35)
    RICHARD E. A. ROBERTSON

    Located at the eastern edge of the Caribbean plate where it borders with the North and South America plates, the Lesser Antilles is a region of high seismicity, tectonism, and active volcanism that typifies oceanic-island arc volcanism. The island chain forms an 850-km arc that is convex toward the Atlantic and extends from Sombrero in the north to the southern island of Grenada. The arc splits north of St. Lucia into two: an Eocene-to-Miocene eastern arc and a Pliocene-to-Recent western arc. The northeastern islands extending from Marie Galante to Sombrero are characterized by Cenozoic limestones and are called the Limestone...

  13. ANTS
    (pp. 35-41)
    BRIAN L. FISHER

    The rise of ants to ecological dominance has been called one of the great epics in evolution. The same features associated with their ecological success also make them destructive invaders. Islands provide an exceptional model for studying ant dispersal, extinction, and radiation. Ants often reach oceanic islands via accidental “sweepstake routes,” leading to a unique cluster of ant species on different islands. The chance dispersal to islands results in high species turnover between islands and within islands over time. The composition of the ant fauna on any particular island can therefore reflect the age, size, and relative isolation of the...

  14. ARCHAEOLOGY
    (pp. 41-47)
    MARSHALL I. WEISLER

    Archaeology is the systematic study of material remains. The diversity of island environments and biota presents fascinating opportunities for studying the evolution of Oceanic societies that developed from ~40,000 to ~800 years ago.

    The vast expanse of the Pacific Islands hosted the greatest maritime migration in human history. Venturing across uncharted waters, Pacific colonists over millennia developed remarkable voyaging skills; built massive double-hulled sail-rigged canoes up to 10 m long; and carried vital plants, animals, and indeed the mental templates of their community layouts or “transported landscapes,” to every speck of land in this watery world known as Oceania. This...

  15. ARCTIC ISLANDS, BIOLOGY
    (pp. 47-55)
    INGER GREVE ALSOS, LYNN GILLESPIE and YURI M. MARUSIK

    Arctic islands constitute a major part of the arctic land masses. Low temperatures and short summers are strong environmental filters that exclude most organisms from living there. Thus, the diversity of most species groups is lower on arctic islands than on the arctic mainland and more southern latitudes. Arctic species exhibit many different adaptations to cope with these harsh environmental conditions.

    Repeated periods of glaciation during the Pleistocene have strongly influenced the biota of arctic islands. During the Last Glacial Maximum (LGM; about 20,000 years ago), major ice caps wiped out most species in the Canadian Arctic Archipelago (CAA) Greenland,...

  16. ARCTIC ISLANDS, GEOLOGY
    (pp. 55-59)
    MICHAEL J. HAMBREY

    The geological history of the Arctic spans nearly four billion years and includes some of the oldest rocks on Earth. A vast range of sedimentary, igneous, and metamorphic rocks are present, but few were formed in their current position. The geological record for many Arctic islands reflects the drift of fragments of continental crust from a position south of the equator to their current polar position. As a consequence, the rocks record a range of climates from tropical to glacial, as well as a fascinating glimpse of biological evolution from the algae of the Precambrian to the high-order animals and...

  17. ARCTIC REGION
    (pp. 59-61)
    STEPHEN D. GURNEY

    The Arctic is that region of the northern hemisphere where the sun, for some time in summer, does not set and, for some time in winter, does not rise. It is a land of contrasts, of the polar night and the polar day, and its southerly limit is the Arctic Circle at a latitude of 66°33′ N. Islands within the Arctic region (see Fig. 1) include the Canadian Arctic islands, Greenland (considered to be the largest island on the planet) and its surrounding islands, Jan Mayen, Bjørnøya, the Svalbard archipelago, the Lofoten Islands, and the islands of the Russian Arctic...

  18. ASCENSION
    (pp. 61-63)
    DAVID M. WILKINSON

    Remote oceanic islands such as Ascension have long played an important role in the study of ecology and evolutionary biology. Although historically less important for these subjects than the Galápagos, Ascension was visited by some of the leading nineteenth-century traveling scientists, including Charles Darwin and Joseph Dalton Hooker, and it has a range of endemic species of both scientific and conservation importance.

    Ascension is a volcanic island located in the tropical south Atlantic (7°57′ S, 14°22′ W) with an area of about 97 km². Much of its scientific interest comes from its remote location. The nearest point in Africa is...

  19. ATLANTIC REGION
    (pp. 63-67)
    ANDREAS KLÜGEL

    The Atlantic is the world’s second largest ocean, forming an elongated basin between the Arctic Ocean in the north and Antarctica in the south. It owes its existence to the break-up of the supercontinent Pangaea, which began around 180 million years ago in the North Atlantic and 130 million years ago in the South Atlantic. Today the Atlantic continues to widen at rates of approximately 1.8–3.5 cm per year by seafloor spreading along the Mid-Atlantic Ridge, a submarine mountain range separating the ocean into an eastern and a western basin. The Atlantic harbors a number of islands of mostly...

  20. ATOLLS
    (pp. 67-70)
    EDWARD L. WINTERER

    Atolls are a special type of coral reef complex formed in tropical seas by a ring of reef coral enclosing a lagoon. The characteristic features of an atoll include a reef rim, from 100 to 500 m across, which is mainly awash at high tide, and flattish islands (motu), which remain a few meters above sea level and on which people may live. The wordatollitself comes from the language of the Maldive Islands, a chain of large atolls in the Indian Ocean (Fig. 1). Atolls range in size from a few to as many as 40,000 km², and...

  21. AZORES
    (pp. 70-75)
    PAULO A. V. BORGES, ISABEL R. AMORIM, ROSALINA GABRIEL, REGINA CUNHA, ANTÓNIO FRIAS MARTINS, LUíS SILVA, ANA COSTA and VIRGíLIO VIEIRA

    The Azores are a remote and geologically recent archipelago consisting of nine volcanic islands located in the North Atlantic Ocean (Fig. 1). Of the 4467 species and subspecies of terrestrial plants and animals known to inhabit this archipelago, 420 are endemics. These islands were discovered in the fifteenth century, and more than 500 years of human settlement have taken their toll on the local fauna and flora. Approximately 70% of the vascular plants and 58% of the arthropods found in the Azores are exotic, many of them invasive, and only 20% of the archipelago’s terrestrial realm is protected, which raises...

  22. BAFFIN
    (pp. 76-78)
    LYNDA DREDGE

    Baffin Island, with an area of more than 500,000 km², is one of the principal islands of the Canadian Arctic archipelago and the world’s fifth-largest island (Fig. 1). It lies within the territory of Nunavut, at the eastern portal of the Northwest Passage, the grail of early explorers and a potential shipping route inyears to come. Half the island’s 11,000 inhabitants live in Iqaluit, the administrative capital for Nunavut; the remainder live in seven other coastal communities. The island is named after William Baffin, a seventeenth-century British explorer, although it was known previously to the Norse as Helluland, the land...

  23. BAJA CALIFORNIA: OFFSHORE ISLANDS
    (pp. 78-82)
    MARTIN L. CODY

    The Baja (lower) California Peninsula, in extreme northwest Mexico, stretches more than 1000 km south from the southern (Alta) California border to the Tropic of Cancer, spanning latitudes of 32°30′ to 23° N. Originating about 500 km south of its present position and rifting north some 4 cm per year since the Miocene, the peninsula was sheared from the North American plate by contact with the northwesterly moving Pacific plate. The East Pacific Rise runs up the center of the Sea of Cortés (or Gulf of California), which separates the peninsula from mainland Mexico; it continues north as the classic...

  24. BARRIER ISLANDS
    (pp. 82-88)
    MILES O. HAYES

    Barrier islands are elongate, shore-parallel accumulations of unconsolidated sediment, some parts of which are situated above the high-tide line (supratidal) most of the time, except during major storms (see example in Fig. 1). They are separated from the mainland by bays, lagoons, estuaries, or wetland complexes and are typically intersected by deep tidal channels called tidal inlets. A large percentage of the major barrier islands of the world occur along the coastlines of the trailing edges of continental plates and of epicontinental seas and lakes (e.g., Caspian and Black Seas). Because they are composed of unconsolidated sediments (primarily sand, with...

  25. BARRO COLORADO
    (pp. 88-91)
    EGBERT GILES LEIGH JR.

    Barro Colorado is a 1500-ha island situated at 9°9′ N, 79°51′ W in central Panama, first isolated from the surrounding mainland in 1914 by the rising waters of Gatun Lake, after the Chagres River was dammed to form part of the Panama Canal. The island is covered by seasonal tropical forest, half of it old growth, which offers beauty and fascination enough to fill any biologist’s lifetime. Barro Colorado’s primary claim to the reader’s attention is its contribution to our understanding of tropical biology.

    The governor of the Canal Zone declared this island a reserve in 1923 in response to...

  26. BEACHES
    (pp. 91-94)
    BRUCE RICHMOND

    Beaches are shoreline accumulations of loose sand, gravel, or a mixture of the two, that are formed primarily by the action of waves. Beach sediment can be derived from a variety of sources including insular shelves, the adjacent land and upland sources, or other beach locations through alongshore movement of material. Beaches provide critical coastal habitat, such as nesting sites for sea turtles; they act as a buffer protecting adjacent land from storm wave attack; and they are an important cultural and recreational resource. Island beaches are the same as those on the continents, but island beach characteristics typically change...

  27. BERMUDA
    (pp. 95-98)
    ANNE F. GLASSPOOL and WOLFGANG STERRER

    Located at 32°18′ N, 64°46′ W in the Sargasso Sea (northwestern Atlantic Ocean), Bermuda is a small, low-lying oceanic archipelago of solidified wind-blown dunes (aeolianite) lying atop an eroded volcanic platform. Because of the Gulf Stream’s influence Bermuda boasts a subtropical climate that supports the world’s northernmost coral reef and mangrove systems.

    The Bermuda Seamount originated at least 33 million years ago, probably on top of a much earlier eruptive episode (110 million years ago), as a towering mid-ocean volcano with two side peaks (now Challenger Bank and Argus Bank). Drifting westward on the North American Plate, the extinct volcano...

  28. BIOLOGICAL CONTROL
    (pp. 99-103)
    MARK GILLESPIE and STEVE WRATTEN

    Biological control (or biocontrol) is the use of natural enemies to suppress pest species populations to less damaging densities. When certain native and introduced invertebrates, plants, pathogens, and vertebrates increase in abundance and become pests through human influence or through other causes, economic crop damage and threats to natural resources are likely. Islands are particularly vulnerable to pest outbreaks. With high endemism, low species diversity, small land areas, and a history less affected by forces that develop adaptability compared to continents, islands are more susceptible to the effects of habitat changes and species introductions. The enhancement of the efficacy of...

  29. BIRD DISEASE
    (pp. 103-105)
    DAVID CAMERON DUFFY

    Bird diseases have had a profound effect on some island avifauna, but, as with human diseases, our full understanding of their extent and impact has been limited by isolation, the paucity of qualified observers, and the possibility that many of the strongest effects have already occurred. Despite these limitations, research suggests that bird diseases on islands fall into two main, contrasting groups, both the result of human intervention: alien diseases attacking naïve, susceptible populations, with often devastating effects on an island’s species and ecosystems, and (more rarely) “emerging diseases,” resulting from human contact with endemic avian pathogens on previously isolated...

  30. BIRD RADIATIONS
    (pp. 105-111)
    JEFFREY PODOS and DAVID C. LAHTI

    Bird radiations provide informative illustrations of ecological and evolutionary processes, including those that help to generate biodiversity as ancestral species radiate into multiple descendent species. Adaptive radiation involves initial phases of divergence among populations or incipient species, accompanied by or followed by the evolution of reproductive isolation. In this article, aspects of these two key processes—divergence and the evolution of reproductive isolation—are outlined and examined with specific reference to island bird radiations.

    Island habitats provide biologists valuable if not unique opportunities for the study of ecology, evolution, and animal behavior. Relative to continental habitats, islands tend to express...

  31. BORNEO
    (pp. 111-116)
    SWEE-PECK QUEK

    Straddling the equator between 7° N and ~4° S at the southeasternmost extremity of the Eurasian continental crust, Borneo, at ~740,000 km², is the third largest island after Greenland and New Guinea. Early explorers in the Indo-Malaysian archipelago encountered a Borneo that was cloaked in dense rain forests from coast to coast and inhabited by headhunting tribes. The original forests of Borneo have been reduced to about half their former extent but still hold an exceptionally rich biota teeming with endemics. Borneo’s forests rank among the most diverse of the world’s rain forests, and, as recently as 2005, have even...

  32. BRITAIN AND IRELAND
    (pp. 116-126)
    ROSEMARY G. GILLESPIE and MARK WILLIAMSON

    Britain and Ireland are a pair of archipelagoes of which the island of Britain, which comprises most of England, Scotland and Wales, is the largest (Fig. 1). The next largest island is Ireland, comprising Northern Ireland, which is part of the United Kingdom (UK), and the Irish Republic. The islands range from 60°51′ N in the north (Muckle Flugga, Shetland Islands) to 49°51′ N (Pednathise Head, Isles of Scilly) in the south, and from 10°35′ W in the west (Tearaght Island, Kerry, Ireland) to 01°45′ E in the east (Lowestoft, Suffolk, England). The total area of the UK is about...

  33. CANARY ISLANDS, BIOLOGY
    (pp. 127-133)
    JAVIER FRANCISCO-ORTEGA, ARNOLDO SANTOS-GUERRA and JUAN JOSÉ BACALLADO

    The Canary Islands have an area of 7447 km² and are located close to the northwestern Saharan coast (~28° N latitude and 16° W longitude). They are composed of seven volcanic islands and a few islets. Several environmental factors contribute to the ecological peculiarities of these islands including the heavy influence of the cold Oceanic Canary current and the northeastern trade winds, the altitude (the highest mountain of Spain, Peak Teide [3718 m], is located on Tenerife [Fig. 1]), the occasional dry winds from the Western Sahara, the high elevation anti-trade dry winds from tropical latitudes, and a topography highly...

  34. CANARY ISLANDS, GEOLOGY
    (pp. 133-143)
    KAJ HOERNLE and JUAN-CARLOS CARRACEDO

    The Canary Islands, located between 100 and 500 km from the coast of northwestern Africa (Morocco), consist of seven major volcanic islands forming a rough west-southwest to east-northeast trending archipelago. Together with the Selvagen Islands and a group of seven major seamount complexes (some of which were former Canary Islands) to the northeast, they form the Canary volcanic province. Volcanism in this ~800-km-long and ~400-km-wide volcanic belt (located at 33–27° N and 18–12° W) decreases in age from the northeast (Lars Seamount, 68 million years) to the southwest (Hierro Island, 1 million years) and is interpreted to represent...

  35. CAPE VERDE ISLANDS
    (pp. 143-148)
    MARIA CRISTINA DUARTE and MARIA MANUEL ROMEIRAS

    Cape Verde’s natural heritage is unique. The physical environment of these islands creates a multiplicity of habitats with a great wealth of fauna and flora. Nevertheless, this biodiversity is naturally restricted to the narrow geographical limits of the islands and is extremely vulnerable to disturbances caused by human activities. The threatened island endemics are thus likely to benefit from conservation management programs that are urgently needed if Cape Verde’s natural levels of diversity are to be maintained.

    The Cape Verde archipelago is grouped together with the Azores, Madeira, the Selvagens, and the Canary Islands in the Macaronesian region, which is...

  36. CAROLINE ISLANDS
    (pp. 148-150)
    JAMES R. HEIN

    The Caroline Islands form an archipelago just north of the equator in Micronesia, western Pacific. At various times in the past, the Caroline Islands encompassed all the islands that now comprise the Federated States of Micronesia (FSM), the Republic of Belau (formerly known as Palau), Guam and the southern Mariana Islands, and the southwestern islands of the Republic of the Marshall Islands (Fig. 1). Today, the name Caroline Islands refers to only the islands of the FSM and Belau (sometimes referred to as Palau).

    The earliest settlement of Micronesia is thought to have occurred about 2000 years ago, when immigrants...

  37. CAVES, AS ISLANDS
    (pp. 150-154)
    DAVID C. CULVER and TANJA PIPAN

    At a very simple level, there is an analogy between real islands and the “virtual islands” of caves. Caves are islands of cavities surrounded by impenetrable rock and connected only by the “ocean” of the surface. Landscapes with caves are island-like at several scales, from the small solution pockets above caves (epikarst) to their subterranean drainage basins. They are island-like in evolutionary time. Many cave species have evolved unique morphological traits—reduced or missing eyes, reduced or missing pigment, elaboration of appendages, and hypertrophy of extrasensory structures. They are also island-like in ecological time, and dispersal among “islands” can occur,...

  38. CHANNEL ISLANDS (BRITISH ISLES)
    (pp. 154-155)
    EDWARD P. F. ROSE

    The Channel Islands are British Crown Dependencies situated close to the Normandy coast of France (Fig. 1): Jersey (116 km²); Guernsey (64 km²); Alderney (8 km²); the lesser islands of Sark, Herm, Jethou, and Brecqhou; and adjacent (mostly uninhabited) islets, rocks, and reefs. Their laws and administrative systems are distinct from those of England, and therefore the United Kingdom, having been independently derived from the medieval Duchy of Normandy. Each of the four largest islands is largely self-governing, but Jersey and Guernsey form the centers of two separate bailiwicks with, among other differences, their own postage stamps, banknotes, and coinage....

  39. CHANNEL ISLANDS (CALIFORNIA), BIOLOGY
    (pp. 155-161)
    AARON MOODY

    The California Channel Islands lie near the coast of southwestern California between Point Conception and the U.S.–Mexico border (Fig. 1, Table 1). They contain a rich terrestrial flora and high rates of floral and faunal endemism. The islands also provide significant foraging and breeding habitat for marine mammals and seabirds, and they harbor rich and productive rocky intertidal and kelp forest communities. Introduced taxa constitute a major component of the terrestrial biota, and the legacies of uncontrolled livestock ranching from the mid-nineteenth to the late twentieth century are readily observed today. The islands are considered to have high conservation...

  40. CHANNEL ISLANDS (CALIFORNIA), GEOLOGY
    (pp. 161-164)
    JANET HAMMOND GORDON

    The geology of California’s Channel Islands records the transition of the North American plate boundary from a subduction zone to a transform boundary that is now the San Andreas fault. This transition was particularly complex at the latitude of the Channel Islands. Geological evidence on the islands indicates that some were rotated and translated by as much as 300 km up the California coast from San Diego. Others are the product of concurrent rifting and volcanism.

    The Channel Islands reside in the California Continental Borderland, the offshore area between the continental slope and the coast (Fig. 1). The borderland has...

  41. CICHLID FISH
    (pp. 165-169)
    OLE SEEHAUSEN

    To lake-adapted fish, lakes are what islands in the sea are to continental organisms. Extraordinarily diverse species assemblages have evolved, some during surprisingly short timespans, in many African lakes. These can help us understand the mechanisms behind the phenomenon of adaptive radiation in island biota. The group of organisms that by far exceeds all others in terms of its endemic lacustrine species diversity is cichlid fish, a group of secondary freshwater fishes, members of the large ancient marine radiation of perchlike fish. Altogether, some 1300 to 1500 species of cichlids are endemic to the African Great Lakes.

    The perchlike cichlid...

  42. CLIMATE CHANGE
    (pp. 169-171)
    DAVID A. BURNEY

    Climate changes are well documented for islands throughout the world on many scales, from hundreds of millennia to recent decades. These changes in temperature and moisture have had large effects on many other ecological factors, including sea level, coastal dynamics, biogeography, extinctions, and human culture. Climate changes on islands have varied in severity according to the size of the island, its latitude and elevation range, and the effects of human activities. Climate changes predicted for the near future can be expected to have drastic effects on all islands, even to the point of destroying some island ecosystems, challenging human lifeways...

  43. CLIMATE ON ISLANDS
    (pp. 171-174)
    THOMAS A. SCHROEDER

    Climate is the average of weather conditions over a long period of time. The period is at least 30 years. The standard weather parameters considered are temperature and precipitation, which are primary controls on distributions of vegetation. In addition to the average conditions, the variance of these conditions is equally important. Year-to-year or decade-to-decade oscillations in climate constitute “variability”; long-term trends constitute climate “change.” Climate on islands depends upon a number of geographical and physical conditions.

    A primary control on island climate is the climate of the surrounding ocean and atmosphere. Latitude is a major factor. Atmospheric and ocean circulations...

  44. COLD SEEPS
    (pp. 174-177)
    CHARLES K. PAULL

    Cold seeps are springs that carry waters at near-ambient temperatures containing dissolved hydrogen sulfide, methane, and other hydrocarbons from subsurface aquifers out onto the sea floor. The sea floor environment surrounding cold seep sites is profoundly altered as a consequence of the chemical and biological reactions that occur when these reduced compounds encounter the oxygenated waters at the ocean floor. Many of the biological communities and geochemical processes that occur around cold seeps are similar to those found at deep-sea hydrothermal vents. Additional heat, however, is not of primary importance to either the biology or the geochemical reactions occurring at...

  45. COMOROS
    (pp. 177-180)
    D. JAMES HARRIS and SARA ROCHA

    The Comoros are a set of four major oceanic islands—Mayotte (Maore), Anjouan (Ndzuani), Moheli (Mwali), and Grand Comoro (Ngazidja)—and surrounding islets, situated in the middle of the Mozambique Channel, approximately halfway between Madagascar and the East African coast (about 300 km from each) in the southwestern Indian Ocean (Fig. 1). Like most other oceanic island groups, the numbers of species found in the Comoros is much lower than that found in nearby continental systems, but there is a high degree of endemism. The greatest conservation issues for the islands revolve around their high population density, which has led...

  46. CONTINENTAL ISLANDS
    (pp. 180-187)
    DAVID M. WATSON

    As evidenced by the breadth of systems covered in this volume, the term “island” can be applied to a range of ecosystems extending well beyond conventional notions of land masses surrounded by water. Be they caves, rock outcrops, mountaintops, or oases, these systems share many biotic and abiotic features with their oceanic counterparts. One of the primary distinctions between different island systems is whether they were formed de novo, or instead formed by fragmentation. In the former case, the islands have never been in contact with the source of colonists and have abundant “empty” ecological niche space. Fragments are fundamentally...

  47. CONVERGENCE
    (pp. 188-191)
    TADASHI FUKAMI

    In ecology and evolutionary biology, the term “convergence” refers to intriguing resemblance in the characteristics of distantly related organisms or in the structure of independently developed communities. These phenomena are thought to be caused by similarity in the environmental conditions affecting the organisms or communities. Convergence is observed on both islands and continents, but it can be more striking and more easily identified on islands, particularly when they are remotely located from other land masses.

    Different species living under similar environmental conditions sometimes show close resemblance to one another in appearance, habit, and lifestyle, even if they are distantly related...

  48. COOK ISLANDS
    (pp. 191-197)
    TEGAN HOFFMANN

    Located in the heart of the tropical South Pacific between the Society Islands to the east, Tonga and Samoa to the west, and New Zealand about 3500 km to the southwest, the Cook Islands are part of Polynesia. The nation’s 15 islands range from the towering, volcanic Rarotonga, the country’s largest island and capital, to the northern solitary atolls. Divided into a Northern Group of six low-lying, sparsely populated atolls and, 1000 km away, a Southern Group of nine fertile, volcanic, and elevated islands, where most of the population (estimated at 21,000 in 2007) lives, the Cook Islands lie south...

  49. CORAL
    (pp. 197-203)
    DAPHNE G. FAUTIN and ROBERT W. BUDDEMEIER

    The term “coral” is neither scientific nor precise. This article focuses on those cnidarian polyps capable of secreting skeletons that contribute to formation of reefs, which can produce or play a role in producing islands. These skeletons consist of the mineral calcium carbonate, deposited in the crystal form aragonite. These corals are among the few animals that shape the environment in a profound and large-scale manner—that are biogeomorphic agents.

    The many meanings of the word “coral” occupy a full page of theOxford English Dictionary. The first entry refers to the skeleton made by some animals of the phylum...

  50. COZUMEL
    (pp. 203-206)
    ALFREDO D. CUARÓN

    Cozumel (~478 km²) is the largest island in the Mexican Caribbean Sea, a site of historical and cultural significance, a popular international resort, and an area of global biodiversity conservation priority. It is located 17.5 km off the northeast coast of the Yucatán Peninsula (20°6'18.2" to 20°5'32.8" N; 86°3'23.3" to 87°01'31.1" W). It is an oceanic island of coralline origin, which is separated from the mainland by the 400-m-deep Cozumel Channel. Maximum altitude is just over 10 m. The weather is humid tropical, with mean annual temperature of 25.5 °C and mean annual rainfall of 1505 mm.

    The name Cozumel...

  51. CRICKETS
    (pp. 206-212)
    DANIEL OTTE and GREG COWPER

    Virtually all oceanic islands within the tropics and subtropics are occupied by crickets, both those that colonized the islands on their own and those that appear to have been carried there by humans. Islands in the temperate zone are not occupied, probably because crickets are adapted mainly to warmer areas. The diversity of crickets on some islands, as measured by the number of species per unit area, is extraordinary, with Hawaii being more than 2000 times as rich, having at least twice as many cricket species as the continental United States and Canada combined.

    Which cricket groups radiate on an...

  52. CYPRUS
    (pp. 212-216)
    IOANNIS PANAYIDES

    Cyprus is one of the largest Mediterranean islands, with a surface area of 9251 km². It lies in the northeastern corner of the Mediterranean Sea approximately centered on latitude 35° N and longitude 33° E. Two mountain ranges dominate the topography of the island, the Troodos Range in the central region and the Pentadaktylos Range in the north. Between the two ranges lies the Mesaoria Plain, which, together with the narrow alluvial plains along the coast, makes up the bulk of the arable land. Most of the rivers, which flow only in the winter, spring out of the Troodos Mountains,...

  53. DARWIN AND GEOLOGIC HISTORY
    (pp. 217-221)
    JAMES H. NATLAND

    Before Charles Darwin (1809–1882; Fig. 1) was a biologist, he was a geologist. He is remembered for developing the theory of evolution, but the first independent scientific work he ever did was on the geology of a volcanic island, the one he called St. Jago (Santiago), in the Cape Verde archipelago. This was the first landing on the five-year round-the-world voyage of HMSBeagle, the celebrated expedition on which he served throughout as social companion to Robert FitzRoy (1805–1865), the ship’s master and commander, and also as naturalist. Of the 15 field notebooks Darwin compiled about his shore...

  54. DEFORESTATION
    (pp. 221-224)
    BARRY V. ROLETT

    Deforestation is the loss of trees involving a vegetational succession from forest cover to some other kind of landscape. It causes reduced biodiversity and, under certain conditions, promotes the development of wastelands. The process of deforestation is intertwined with human history as well as with the influence of climate and other environmental factors. Islands are particularly vulnerable to deforestation because their ecosystems tend to be fragile and susceptible to rapid change.

    Historical records offer abundant evidence for deforestation, especially in relation to the loss of trees through the development of agriculture and timber industries. Records for the Philippines show, for...

  55. DISPERSAL
    (pp. 224-228)
    ISABELLE OLIVIERI

    Dispersal (or migration) can be defined as any movement of individuals with potential consequences for gene flow across space. Dispersal can be extended to include movement through time (i.e., dormancy). Dispersal is a fundamental life history trait, with multiple demographic and genetic consequences. In particular, it determines the amount of local adaptation and the likelihood of various speciation mechanisms. It is also an evolving trait.

    Overall, the different causes for dispersal evolution can be classified into three broad classes of explanation. First, the evolution of dispersal may be understood in the light of habitat selection theory, whereby behaviors at departure...

  56. DODO
    (pp. 228-232)
    J. P. HUME

    The dodo,Raphus cucullatus(family Columbidae), has become one of the most famous birds in the world, a true icon of extinction, with probably more written about it than any other species, yet we know practically nothing about the bird in life. Contemporary accounts and illustrations are often contradictory, plagiarized from earlier sources or simply manufactured from pure imagination. This has resulted in a wealth of scientific myths and misconceptions based on totally inadequate source material.

    The volcanic and isolated Mascarenes Islands, comprising Mauritius, Réunion, and Rodrigues, are situated in the western Indian Ocean. Mauritius, the home of the dodo,...

  57. DROSOPHILA
    (pp. 232-235)
    PATRICK M. O’GRADY, KARL N. MAGNACCA and RICHARD T. LAPOINT

    The genusDrosophilaprovides excellent opportunities to study evolution on island systems. The endemic HawaiianDrosophilaare a classic example of adaptive radiation and rapid speciation in nature evolving in situ over the course of the past 25 million years. Other groups ofDrosophila, found on true islands or in island-like systems (e.g., the Madrean Archipelago), are invaluable tools to understanding evolutionary biology and have served as theoretical and empirical model systems for over 50 years.

    The endemic Hawaiian Drosophilidae, with an estimated 1000 species, consists of two major lineages, the HawaiianDrosophilaand the genusScaptomyza. The high degree...

  58. DWARFISM
    (pp. 235-239)
    SHAI MEIRI and PASQUALE RAIA

    Insular dwarfism is a tendency of many island animals to evolve a smaller size than their ancestors on the near mainland. Dwarfism may be relatively minor but can sometimes be drastic, with some Mediterranean island elephants reduced in weight by up to 99%. The main selection pressures thought to promote dwarfism involve responses to resource limitation, small prey size, and enhanced reproductive output (in mammals). Dwarfism may more easily be attained on islands that lack, or have fewer, competitors and predators. Whereas members of some clades (e.g., ungulates) dwarf regularly on islands, others have a much wider range of size...

  59. EARTHQUAKES
    (pp. 240-244)
    PAUL OKUBO and DAVID A. CLAGUE

    An earthquake is a sudden movement in the Earth, occurring sufficiently quickly that the movement generates seismic waves. Basic descriptors of an earthquake are origin time, location or hypocenter, and magnitude, which are inferred by analyzing the times and amplitudes of seismic wave arrivals at recording stations equipped with seismographs. Although the vast majority of earthquakes recorded worldwide are small and are detected only by sensitive instruments that gauge the radiated seismic waves, large earthquakes can have widespread and devastating effects. Large earthquakes are also capable of triggering tsunamis when they occur at shallow depths in submarine or near-coastal regions....

  60. EASTER ISLAND
    (pp. 244-251)
    GRANT McCALL

    Rapanui (Easter Island) is the world’s most remote continuously inhabited place, with a unique environment, astonishing traditional evolution, and tragic, but ultimately triumphant, modern history of contemporary development of its vigorous and adaptable population.

    “Easter Island,” after the Christian holy day on which Europeans first arrived there, is the international name, translated into the various world languages, for the place. “Rapanui” is the name and spelling used mostly by the Islanders themselves for their language, themselves, and their island. “Rapa Nui” is the rendering used in official Chilean sources, as the island is an autonomous region of that South American...

  61. ECOLOGICAL RELEASE
    (pp. 251-253)
    ROSEMARY G. GILLESPIE

    Ecological release is the expansion of range, habitat, and/or resource usage by an organism when it arrives in a community from which some members are lacking (Fig. 1); effectively, it indicates the difference between the fundamental and realized niche of a species. The phenomenon has frequently been described for species upon initial colonization of islands, where communities may have lower species diversity, or where the existing predators/parasites are not yet capable of exploiting the newly arriving species. For example, Puercos Island (Pearl Archipelago off Panama) has far fewer species of resident birds compared to the mainland, though the density of...

  62. ENDEMISM
    (pp. 253-258)
    QUENTIN C. CRONK and DIANA M. PERCY

    Island organisms are often not found elsewhere and are taxa distinct from their closest relatives on continental landmasses. This phenomenon is called island endemism. Island endemics may be relicts (paleoendemics) or may be of more recent origin (neoendemics). The evolutionary processes leading to endemism often involve evolutionary radiation (i.e., the rapid evolution of many, often ecologically separated, species from the original single founding species).

    The term endemic (endémique), as used for geographically restricted organisms, dates to the Swiss botanist and pioneer biogeographer Augustin Pyramus de Candolle in his 1820 essay “Géographie botanique” that appeared in Cuvier’sDictionnaire des Sciences Naturelles....

  63. EPHEMERAL ISLANDS, BIOLOGY
    (pp. 258-259)
    SOFIE VANDENDRIESSCHE, MAGDA VINCX and STEVEN DEGRAER

    Next to islands constituted of real land masses, the surface of oceans and seas is littered with ephemeral floating objects of various sizes and materials, which form isolated and distinct habitats within the quite uniform marine surface layer. Because of the provision of shelter, surface for attachment, and in many cases also additional food sources, these floating objects attract a wide variety of invertebrates, fishes, and birds. The association behavior of the encountered species and their use of the transient resources offered by floating objects have a considerable impact on the composition, biogeography, and ecology of the marine fauna.

    The...

  64. EPHEMERAL ISLANDS, GEOLOGY
    (pp. 259-260)
    KAZUHIKO KANO

    The term “ephemeral island” has been informally applied to a piece of land that is completely surrounded by water or that emerged out of water and is fated to disappear on a time scale of hours to years after its appearance. This term has also been applied to pumice rafts and other floating objects. Ephemeral islands have the potential to temporarily provide organisms with a shelter, a surface for attachment or spawning, and a food source.

    Ephemeral islands are diverse in birth and fate. They appear and disappear during dynamic surface processes including floods, volcanic eruptions, and even activities of...

  65. EROSION, COASTAL
    (pp. 261-263)
    WAYNE STEPHENSON

    Coastal erosion is the landward retreat of a datum such as mean high water or a geomorphic feature such as a cliff or beach. The landward retreat is persistent through time as distinct from cyclic fluctuations in the position of the shoreline associated with storm erosion and recovery, typical of beaches. Coastal erosion is also widespread, with 70% of the world’s beaches said to be eroding, and 80% of the world’s total shoreline composed of eroding cliff and rock morphologies. Islands are particularly susceptible because of their geomorphic settings and limited sediment supply. Although coastal erosion is typically viewed as...

  66. ERUPTIONS: LAKI AND TAMBORA
    (pp. 263-271)
    T. THORDARSON

    The 1783–1784 Laki (Iceland) and 1815 Tambora (Indonesia) eruptions both took place at volcanoes situated on islands and are the two largest volcanic eruptions on Earth in the last 250 years. They had significant environmental and climatic impacts, despite contrasting eruption style and magma composition (Table 1).

    The eight-month long Laki eruption (June 8, 1783–February 7, 1784) in Iceland is the second largest flood lava event in historic time (Fig. 1), after its neighbor the 934–940 Eldgá eruption. We know more about the Laki eruption than any other of its kind because it is described in many...

  67. ETHNOBOTANY
    (pp. 271-276)
    W. ARTHUR WHISTLER

    Ethnobotany is the study of the relationship between plants and people, but in practice it is usually applied to the use of plants in the developing world (i.e., in cultures other than mainstream “First World” countries). It includes the study of how plants are used and managed as food, medicine, housing materials, cordage, textiles, cosmetics, dyes, and other artifacts and practices that are a part of all cultures. It is considered to be part of ethnobiology, which also includes ethnozoology, but because the majority of most cultures’ needs are met by plants, ethnobotany is the more commonly used term for...

  68. EXPLORATION AND DISCOVERY
    (pp. 276-281)
    SCOTT M. FITZPATRICK

    One of the greatest achievements in human history was the construction of seaworthy craft and navigational aids that allowed people to move across the world’s seas and oceans and to eventually colonize islands. Archaeological evidence indicates that hominids have been able to cross water gaps since the Pleistocene (at least by 750,000–800,000 years ago) and thatseafaring(rather thanseagoing, which as the archaeologist Cyprian Broodbank has noted, implies tentative or “culturally enhanced floating”) has been practiced for at least 40,000 years. It was not until much later, during the Middle to Late Holocene, that humans began voyaging across...

  69. EXTINCTION
    (pp. 281-286)
    KEVIN J. GASTON

    In varied combinations, three processes shape the size and composition of the species assemblages occurring on individual islands. Gains in species numbers arise through speciation and the immigration of individuals from elsewhere (other islands or mainland areas). Losses in species numbers take place through extinction. Global extinction occurs when the last individual of a species dies, although one might qualify this by distinguishing between the outright loss of all individuals and extinction in the wild (with individuals remaining in cultivation or captivity). Local extinction, or extirpation, occurs when the last individual of a given population dies, such as the population...

  70. FARALLON ISLANDS
    (pp. 287-291)
    PHIL CAPITOLO

    The Farallon Islands (Farallones) consist of several sparsely vegetated rocks about 47 km west of San Francisco, California. The South Farallones include Southeast Farallon Island (SEFI), West End Island (WEI), and several adjacent seastacks, totaling less than 50 hectares. The North Farallones are four steep islets about 11 km northwest of SEFI, totaling less than 10 hectares. Middle Farallon is a small, wave-washed rock 3.5 km northwest of SEFI (Fig. 1). The Farallones are perched on the edge of the continental shelf in waters about 60 m deep; less than 10 km to the southwest the ocean floor drops abruptly...

  71. FAROE ISLANDS
    (pp. 291-297)
    GINA E. HANNON, SIMUN V. ARGE, ANNA-MARIA FOSAA, DITLEV L. MAHLER, BERGUR OLSEN and RICHARD H. W. BRADSHAW

    The Faroe (or Faeroe) Islands, 61°24′–62°24′ N and 6°15′–7°41′ W, are a series of small islands oriented in a northwest-southeast direction situated in the North Atlantic between Iceland, Norway, and Scotland (Fig. 1). They consist mainly of steep mountainous plateaus with narrow terraces, gorges, and cirque valleys, divided by narrow fjords and sounds. Most of the outer coastal reaches are vertical cliffs several hundred meters in height, which are extremely exposed and subject to erosion by breakers. The islands are slightly tilted, with the eastern parts experiencing some subsidence after the land uplift following the last glaciation, as...

  72. FERNANDO DE NORONHA
    (pp. 297-298)
    R. V. FODOR

    Fernando de Noronha is an east–west trending volcanic archipelago located in the equatorial South Atlantic Ocean 350 km from Brazil (Fig. 1). It is composed of 21 islands and islets for a total area of 26 km². The largest island, 17 km² in area and named Fernando de Noronha, is about 10 km long and 3.5 km at its widest point. Of the 20 other islands and islets, Rata is the next largest, at about 6.8 km². The remaining land comprises a total area of about 2 km². The approximately 3000 inhabitants of Fernando de Noronha are Brazilian citizens,...

  73. FIJI, BIOLOGY
    (pp. 298-305)
    PADDY RYAN

    The Fijian archipelago is centrally located amid the island groups of the southwestern Pacific. Tonga and Samoa are to the east, Vanuatu and the Solomon Islands to the northwest, New Caledonia to the southwest, more distant New Zealand to the south, and Australia to the west. The group consists of between 300 and 844 islands, depending on the authority and on the definition of “island.” There are four major islands: Vitilevu (10,388 km²), Vanualevu (5535 km²), Taveuni (434 km²), and Kadavu (408 km²). Total land area is approximately 18,300 km², which occupies an ocean area of around 650,000 km².

    The...

  74. FIJI, GEOLOGY
    (pp. 305-309)
    HOWARD COLLEY

    The Fiji Archipelago, which is located about 2400 km northeast of Australia, consists of over 300 islands and is dominated by two major islands, Viti Levu and Vanua Levu. Fiji is very unusual for an archipelago in a deep-oceanic setting. Compared to the more typical adjacent island arcs of Vanuatu to the west and Tonga to the east, Fiji has much larger islands; a much more varied sequence of rocks, including plutonic bodies; an abundance of mineral deposits; and a crustal thickness (up to 30 km) that is comparable to that of continental margins. The early history of Fiji is...

  75. FISH STOCKS/OVERFISHING
    (pp. 310-311)
    JON BRODZIAK

    Fish stocks are renewable resources that have been harvested throughout human history. After vast increases in fishery catches during the twentieth century, overfishing is now a worldwide problem. Fishery harvests by island nations currently account for about 20% of worldwide capture production (Fig. 1), with Japan (26%), Indonesia (22%), the Philippines (10%), and Iceland (10%) accounting for about two-thirds of island catches (Fig. 2). Substantial fisheries occur within island ecosystems, which provide forage areas and spawning habitats for diverse species. Island ecosystems are structured by the width of their continental shelf, or lack thereof, and by their relative latitude (tropical...

  76. FLIGHTLESSNESS
    (pp. 311-318)
    CURTIS EWING

    The evolution of flightless species from ancestors capable of flight as a phenomenon linked to islands was formally proposed by Charles Darwin inOn the Origin of Speciesfor beetles from the island of Madeira. Subsequently, it has been shown that a statistically significant correlation exists between flightlessness and island habitats among certain birds, although no significant correlation has been proven among insects.

    In an 1855 letter to Joseph Hooker, Darwin proposed an evolutionary mechanism to explain the observation that 36% of the beetle species in the Madeira Islands lacked or possessed reduced wings, saying “powers of flight would be...

  77. FOSSIL BIRDS
    (pp. 318-326)
    TREVOR H. WORTHY

    Fossil birds are extinct avian species for which there is no historical record. Such taxa may be known from archaeological sites, ranging from a few hundreds of years old (e.g., many islands in Oceania) to a few thousands of years old (e.g., sites in the Mediterranean). Most often they derive from fossil deposits accumulated either by predators, or in pitfall traps in caves, or in water-laid deposits such as in lake and fluvial deposits.

    Birds are found on most islands of the world, and if there is terrestrial vegetation, then landbirds may also be present. Seabirds often nest on islands,...

  78. FOUNDER EFFECTS
    (pp. 326-328)
    MICHAEL C. WHITLOCK

    Because new populations may be founded by a small number of individuals, by chance the new population may be genetically different from its parent population. A population founded by a small group of individuals is likely to have somewhat less genetic variance and different mean phenotypic values from its source population, which may cause the new population to evolve in different ways. Collectively, these changes in the genetic and phenotypic properties of the population are called a founder effect. If the differences between the founding and source populations are great enough, the founding event potentially contributes to the evolution of...

  79. FRAGMENTATION
    (pp. 328-330)
    LUIS CAYUELA

    Fragmentation is a process that occurs when originally extensive and continuous habitats are broken into smaller areas and separated by other habitat or land use types that disrupt the continuity of the original habitat. At the landscape level, this process generates patches of a certain habitat type that somewhat resemble islands embedded within a matrix of distinct habitats. Fragmentation of natural habitats can influence the entire suite of ecological processes, from individual behavior through population dynamics to ecosystem fluxes. Although particular attributes of the environment determine the existence of natural fragments, most recent habitat fragmentation at the landscape level is...

  80. FRASER ISLAND
    (pp. 330-332)
    BRAD BALUKJIAN

    Fraser Island, the world’s largest sand island, is located off the eastern coast of Australia in the state of Queensland and is both a national park and, since 1992, a World Heritage Area. Seven vegetation zones and a multitude of freshwater lakes, including half of the world’s perched lakes, characterize the island’s landscape. Although recently threatened by human impact, the island now has a comprehensive management plan that promises to preserve its stunning natural beauty for years to come.

    Fraser Island is a land-bridge island that covers 1653 km² of land area and is 123 km long by 25 km...

  81. FRENCH POLYNESIA, BIOLOGY
    (pp. 332-338)
    JEAN-YVES MEYER and BERNARD SALVAT

    Despite their small size and remoteness, the numerous tropical and subtropical oceanic islands of French Polynesia (South Pacific) display a rich array of natural marine and terrestrial ecosystems and habitats. The terrestrial biota provide striking examples of plant and animal speciation and adaptive radiation, high levels of endemism, and a huge number of threatened and extinct species. The large variety of coral reef formations, from open atolls to completely closed lagoons, allows a high diversification of the marine biota. These unique biota are highly susceptible to human impact, particularly resulting from habitat destruction, biological invasion of introduced species, and potentially...

  82. FRENCH POLYNESIA, GEOLOGY
    (pp. 338-343)
    ALAIN BONNEVILLE

    French Polynesia is located in the south-central part of the Pacific Ocean, between 5° and 30°S and 130° and 160° W. It comprises 118 islands representing an area of 16,000 km² above sea level and having more than 5 million km² of water within the limits of its huge exclusive economic zone. All of French Polynesia’s islands are basaltic shield volcanoes that represent only the emerged parts of important submarine mountain chains created by volcanic activity beginning 40 million years ago.

    The sea floor of French Polynesia was formed between 25 and 85 million years ago by sea-floor spreading along...

  83. FRESHWATER HABITATS
    (pp. 343-347)
    ALAN P. COVICH

    The remoteness of many islands strongly limits initial dispersal and colonization of insular springs, rivers, and lakes. Colonization of insular freshwaters generally results in some broadly predictable relationships among changes in species richness and the sizes of islands, their locations relative to continental and other island sources of species, and their climate and age. Geologic age, composition of volcanic or sedimentary rocks, and distributions of rainfall all interact to determine the rates of development of drainage networks and availability of aquatic habitats for colonization. Ultimately, the island is completely eroded, its aquatic habitats are filled with sediments, and it is...

  84. FROGS
    (pp. 347-351)
    RAFE M. BROWN

    Frogs and toads (collectively termed anurans), together with salamanders and caecilians (eel-like amphibians), constitute the living members of the clade Lissamphibia, which contains all modern amphibians. Amphibians on islands are of intense interest to evolutionary biologists because of the perceived improbability of amphibians naturally crossing saltwater barriers, combined with the undeniable fact that some frogs seem to be relatively proficient at accomplishing this difficult feat. Frogs, in particular, provide an opportunity for evolutionary biologists to address a variety of evolutionary questions within a well-defined historical perspective.

    The mysterious distribution of frogs on islands has piqued the curiosity of explorers, herpetologists,...

  85. GALÁPAGOS FINCHES
    (pp. 352-356)
    HEATHER FARRINGTON and KENNETH PETREN

    The Galápagos finches, also known as Darwin’s finches, are a group of 15 passerine bird species, 14 of which are endemic to the Galápagos Islands of the equatorial Pacific. The fifteenth species is endemic to Cocos Island off the west coast of Costa Rica. Darwin’s finches are a textbook example of adaptive radiation, and a valuable model for understanding natural selection in a variable environment. Recent advances in genetic technology have answered many questions regarding the evolutionary history of these birds, yet they continue to captivate and puzzle researchers today.

    The Galápagos finches were first recorded and collected by scientist...

  86. GALÁPAGOS ISLANDS, BIOLOGY
    (pp. 357-367)
    TERRENCE M. GOSLINER

    The Galápagos Islands are the classic example that comes to mind when most people think of islands and evolution. From the time of Darwin to the present, the Galápagos have provided remarkable examples of the process of evolutionary change through natural selection. This evolutionary history begins with the formation of new land and continues with its subsequent colonization. From there, new environmental conditions shape the processes of natural selection and adaptation that ultimately result in the appearance of new forms of life that develop novel lifestyles.

    The oldest rocks of the extant archipelago are about 4–5 million years in...

  87. GALÁPAGOS ISLANDS, GEOLOGY
    (pp. 367-372)
    DENNIS GEIST and KAREN HARPP

    The Galápagos Islands are renowned for their flora and fauna, made famous by Charles Darwin’s visit to the archipelago in 1835. Darwin’s visit provided an essential foundation for his seminal work,The Origin of Species, and the Galápagos remain an important location for the study of evolutionary biology. Even though they are less familiar than his biological discoveries, many of Darwin’s most astute observations in the Galápagos were related to the geology of the archipelago. Over the past half century, detailed investigations into the volcanic origins of the islands have revealed that the unique geology of the islands is inextricably...

  88. GIGANTISM
    (pp. 372-376)
    PASQUALE RAIA

    Gigantism is the development of large body size in a species that colonizes an island and remains confined there. In the literature, any island population (or species, if there are no mainland conspecifics alive) is considered gigantic when its average body size exceeds the body size limits of members of the original, mainland population (if living) or of parental species.

    In discussing island gigantism, we must first be sure that the size change was associated with island colonization. To this end, the first step is to compare an island species’s body size to that of its living mainland relative. Although...

  89. GLOBAL WARMING
    (pp. 376-380)
    DAVID R. LINDBERG

    Islands and their biodiversity are especially vulnerable to global warming because there are fewer options on islands than on larger continental land masses. Island geomorphology and geographical position moderate the effects of global warming and determine the relative importance of sea-level rise, changes in temperature regimes, ocean circulation patterns, and storm tracks. Effects on island ecosystems will likely be severe and will translate into severe social and economic impacts for islanders.

    The Earth’s climate changes on a multitude of scales, including seasonal, decadal, centurial, and multimillennial periods. Other than human activities, drivers of climate change include (1) changes in the...

  90. GRANITIC ISLANDS
    (pp. 380-382)
    MILLARD F. COFFIN

    Granitic islands are extensions or fragments of continents that are isolated from major continental land masses by the sea or by lakes and rivers. Such islands are common along the margins of continents as well as in lakes and rivers, and they are relatively rare in mid-ocean settings. Variations in continental topography, changing sea and freshwater levels, plate tectonic processes, isostasy, and resistance to erosion account for the existence of granitic islands.

    Granite, composed mainly of quartz, feldspar, and mica, is an intrusive igneous rock that typically solidifies from its parent magma at depths of 2 km or more within...

  91. GREAT BARRIER REEF ISLANDS, BIOLOGY
    (pp. 382-386)
    HAROLD HEATWOLE

    The biota of the islands of the Great Barrier Reef of Australia varies enormously from island to island owing to the great diversity of geological origins and history of the islands, their differences in isolation from each other and from the mainland, their great latitudinal extent, the extent of disturbance by humans, their diversity of soil, and the variety of weather and patterns of sea currents that impinge upon them. The islands and their resident life are in a continual state of flux.

    There are about a thousand islands on the Great Barrier Reef of Australia, ranging from tiny, bare...

  92. GREAT BARRIER REEF ISLANDS, GEOLOGY
    (pp. 386-388)
    SCOTT G. SMITHERS

    Around 1000 islands occur on Australia’s Great Barrier Reef (GBR), with the exact number varying depending on where the boundaries of the GBR are drawn and how islands are defined (e.g., when is a sand bar an unvegetated cay?). The numbers cited below are for the Great Barrier Reef Marine Park (GBRMP). Two main island types occur: continental high islands and low reef islands. Continental high islands are continental outcrops that were separated from the mainland as rising seas flooded the continental shelf after the last ice age. The low reef islands are accumulations of reef-derived carbonate sediments deposited on...

  93. GREEK ISLANDS, BIOLOGY
    (pp. 388-392)
    KOSTAS A. TRIANTIS and M. MYLONAS

    The Greek islands are heterogeneous in mode and time of formation. They are the only islands with floral and faunal elements originating from three different geographical regions, namely Europe, Asia, and Africa. Additionally, these islands have faced the intensive influence of humans for more than 8000 years.

    Almost one-quarter of the geographical area of Greece consists of islands, which are divided into two major groups: the Aegean to the east of continental Greece and the Ionian to the west. An amazing number of islands and islets (approximately 7582) constitute what is known today as the Aegean archipelago. The southern limit...

  94. GREEK ISLANDS, GEOLOGY
    (pp. 392-396)
    MICHAEL D. HIGGINS

    The geological diversity of the Greek islands reflects long and complex interactions between the Eurasian, Mediterranean (African), and Anatolian tectonic plates. The Mediterranean climate and common paucity of soil have augmented the influence of geology on the cultural development of these islands for the last 5000 years: The nature of the bedrock and water supply has controlled agriculture; exploitation of marble and metals have been important economic activities; volcanic eruptions and earthquakes have directly influenced the lives of the inhabitants. In turn, study of the geology of the islands has contributed much to our knowledge of geological processes elsewhere.

    Two...

  95. HAWAIIAN ISLANDS, BIOLOGY
    (pp. 397-404)
    JONATHAN PRICE

    The biology of the Hawaiian Islands consists of organisms evolving and interacting in an archipelago characterized by extreme isolation, a distinctive geologic history, and a diverse physical environment. The Hawaiian biota exhibits classic examples of the evolution of endemism, the emergence of ecologic traits typical of islands, and the problems associated with human occupancy and invasive species.

    Lying just inside the tropics in the central Pacific, the Hawaiian archipelago is among the most isolated archipelagoes on Earth. The closest point of continental land is the west coast of North America, nearly 4000 km away. The nearest islands of comparable size...

  96. HAWAIIAN ISLANDS, GEOLOGY
    (pp. 404-410)
    DAVID R. SHERROD

    The Hawaiian Islands described here are the eight principal islands of the Hawaiian Ridge, which, including a series of atolls, extends 2600 km to Kure island (Fig. 1). The ridge is the southeastern part of the Hawaiian–Emperor volcanic chain, the balance of which comprises submarine seamounts that reach to Kamchatka. The chain is convincing evidence for a hotspot melting anomaly deep in the Earth’s mantle, even as the stability and depth of some hotspots are being reexamined by new scientific investigations.

    The main Hawaiian Islands are built of 15 emergent volcanoes. Two other volcanoes, although now submerged, were once...

  97. HONEYCREEPERS, HAWAIIAN
    (pp. 410-414)
    ROBERT C. FLEISCHER

    The Hawaiian honeycreepers, presently classified in the subfamily Drepanidinae (also called drepanidines or Hawaiian finches), are a morphologically and ecologically diverse group of more than 56 species of cardueline finches endemic to the Hawaiian Islands. Molecular data and rate calibrations based on geological age of the islands suggest that they radiated from a single colonizing ancestral cardueline species beginning as little as 3–4 million years ago. The Hawaiian honeycreepers are a highly endangered avian group, with about 70% of the species recently extinct (i.e., recent Holocene), and at least ten of the remaining 17 species currently considered endangered.

    Specimens...

  98. HUMAN IMPACTS, PRE-EUROPEAN
    (pp. 414-418)
    PATRICK V. KIRCH

    Islands, and especially truly oceanic islands (such as those situated on the Pacific Plate), offer numerous historical “experiments” of interactions between previously isolated and often vulnerable ecosystems and colonizing human populations. Because of isolation, biotic disharmony, and lack of competition, island biotas are characterized by high species-level endemism and vulnerability to invasive taxa. Pioneering human populations, such as those of the Lapita and later Polynesian groups, introduced a portmanteau biota along with cultural concepts of land use and ecosystem management. Over time spans ranging from greater than 40,000 to less than 1,000 years, these invading human populations and their “transported...

  99. HURRICANES AND TYPHOONS
    (pp. 418-420)
    THOMAS A. SCHROEDER

    “Hurricane” and “typhoon” are regional terms for intense tropical cyclones. Tropical cyclones are warmcore vortices that develop over tropical oceans. Tropical cyclones are more intense and compact than the extratropical cyclones of middle latitudes (Fig. 1). They impact islands through damaging winds, heavy rains, and coastal flooding.

    Tropical cyclone intensity is determined from either sea-level pressure in the storm center or maximum sustained winds anywhere in the vortex. Intensity class terminology is basin- and/or forecast-agency dependent. The United States Navy/Air Force Joint Typhoon Warning Center, which issues forecasts for U. S. interests in the western North Pacific Ocean, classifies systems...

  100. HYDROLOGY
    (pp. 420-424)
    CHRISTIAN DEPRAETERE and MARC MORELL

    Freshwater is often a critical resource on islands. Island hydrology takes into account the specific effects of the surrounding ocean on the physical processes and water resources budget of islands, and the specific approaches and considerations required to understand and manage freshwater on islands.

    Islands are special compared to continents when it comes to water resources. This is a consequence of the defining characteristics of islands: their limited size and remoteness from large sources of freshwater. In general, groundwater is the main freshwater resource, although its predominance depends on the area and relief of the island: the smaller and the...

  101. HYDROTHERMAL VENTS
    (pp. 424-427)
    ROBERT C. VRIJENHOEK

    Deep-sea hydrothermal vents are submarine hot springs located along the global mid-ocean ridge system, in back-arc basins, and on volcanic seamounts. The vents support lush animal communities fueled by reduced sulfur compounds and methane, rather than sunlight. Chemosynthetic microbes are the primary producers at vents, and they, in turn, are grazed and filtered by a variety of animals or hosted as symbionts by others. Dependence on geochemical energy restricts vent-endemic animals to small island-like habitats scattered throughout the world’s oceans. Studies of larval development and ocean circulation coupled with population genetic analyses have revealed a range of physical and biological...

  102. ICELAND
    (pp. 428-436)
    SIGURDUR STEINTHORSSON

    Iceland is the largest volcanic island (103,000 km²) in the Atlantic Ocean. It is one of the most volcanically active places on Earth, with more than 20 eruptions per century, and owing to its northerly location in the middle of the sea, the forces of erosion are very active as well. For these reasons, Iceland is a “natural laboratory” in which a continuous tug-of-war exists between constructive and destructive processes that can be studied in real time as well as in the geological record.

    In terms of global tectonics, Iceland is a hotspot located near a constructive plate boundary. It...

  103. INBREEDING
    (pp. 436-437)
    LEONARD NUNNEY

    Inbreeding is a process central to understanding the genetics of populations. Although usually thought of as the mating of close relatives, more generally inbreeding is the local build-up of genetic similarity due to common ancestry. It can cause genetic differentiation among island populations of the same species and the loss of genetic variability within populations. It can also reduce population survival over the short term by inbreeding depression and over the longer term by compromising the ability of the population to adapt to environmental change.

    The theory of inbreeding was developed by Sewell Wright between about 1920 and 1950. Inbreeding...

  104. INDIAN REGION
    (pp. 437-446)
    FREDERICK A. FREY

    Like the submarine igneous crust of the Indian Ocean, most Indian Ocean islands are predominantly formed of volcanic rock, usually basalt; however, others, such as Sri Lanka, Madagascar, Zanzibar, and the Seychelles archipelago, are predominantly formed of continental crustal rocks, such as granite, sediment, and their metamorphosed equivalents. This article summarizes major geologic and geographic features of many but not all islands within the Indian Ocean basin and discusses the plate tectonic implications of these islands.

    There are three types of geologic settings that lead to basaltic volcanism on Earth.

    Volcanoes form when plates move apart because the melting temperature...

  105. INDONESIA, BIOLOGY
    (pp. 446-453)
    TIGGA KINGSTON

    Indonesia is one of the most biologically rich countries in the world, yet dramatic land-use changes in recent decades place much of this biodiversity in peril. The high levels of species richness and endemism are in large part attributable to a complex geological history that has both generated a profusion of island speciation centers and brought together two very different biological realms.

    Straddling the equator from 6°N to 11°S, the Indonesian archipelago comprises over 18,000 islands that extend from Sumatra in the Paleotropical realm to New Guinea and the Aru Islands in the Notogean (Australian) realm. Between these two extremes...

  106. INDONESIA, GEOLOGY
    (pp. 454-460)
    ROBERT HALL

    Indonesia is a geologically complex region situated at the southeastern edge of the Eurasian continent. It is bordered by tectonically active zones characterized by intense seismicity and volcanism resulting from subduction. Western Indonesia is largely underlain by continental crust, but in eastern Indonesia there is more arc and ophiolitic crust, and several young ocean basins. The Indonesian archipelago formed over the past 300 million years by reassembly of fragments rifted from the Gondwana supercontinent that arrived at the Eurasian subduction margin. The present-day geology of Indonesia is broadly the result of Cenozoic subduction and collision at this margin.

    Indonesia is...

  107. INSECT RADIATIONS
    (pp. 460-466)
    DIANA M. PERCY

    Insect radiations on islands are the evolutionary product of diversification within an insect lineage on an island or a series of islands forming an archipelago. Radiations, by definition, represent in situ diversification and are often characterized by evolutionarily novel adaptations. Island radiations are one of the most important natural phenomena for evolutionary biologists, and, like other animal and plant groups, insects on islands have undergone radiations that range from a modest diversification of species to explosive radiations over a short period of time. Insect radiations vary not only in the numbers of species but in the rates of speciation and...

  108. INSELBERGS
    (pp. 466-469)
    STEFAN POREMBSKI

    Inselbergs are isolated rock outcrops that frequently consist of granites and gneisses and form old landscape elements that are widespread on crystalline continental shields. The environmental conditions on inselbergs are extreme both edaphically (because they lack soil) and microclimatically (because they are exposed to intense irradiation and high temperatures), and their vegetation is thus demarcated against the surroundings. Widespread are desiccation-tolerant lichens, mosses, ferns, and angiosperms.

    Patchily distributed habitats that are dominated by a hard, stony surface are known as rock outcrops when they protrude above the surroundings. This definition encompasses a broad range of landforms such as the tepuis...

  109. INTRODUCED SPECIES
    (pp. 469-475)
    DANIEL SIMBERLOFF

    Introduced species are those brought purposefully or inadvertently by humans to new regions, whereas a biological invasion is the establishment and spread of an introduced species into one or more habitats in its new home. Bio-logical invasions are particularly pronounced on islands; worldwide, ~1.6 times as many mammal species and three times as many bird species have been introduced successfully to islands than to continents. Introduced carnivores eliminated many island bird species and subspecies, as well as reptiles and amphibians. Introduced grazers such as sheep, rabbits, and reindeer have eliminated many endemic island plants, and rooting by introduced pigs has...

  110. INVASION BIOLOGY
    (pp. 475-480)
    GEORGE RODERICK and PHILIPPE VERNON

    A biological invasion is the establishment and spread of a locally nonindigenous species. Invasive species have had significant ecological and economic impacts on islands, including displacement or extirpation of native species, changes in physical geography such as erosion and silting of streams and offshore habitats, and rising costs associated with management of urban and agricultural pests. Invasive species can colonize new areas on their own, inadvertently through actions of humans, or as a result of purposeful introductions with unexpected consequences. With the expansion of global trade and connectivity, the importance of invasive species is intensifying, and biological invasion is appropriately...

  111. ISLAND ARCS
    (pp. 481-486)
    RICHARD J. ARCULUS

    Island arcs are chains of concurrently or potentially active volcanic islands, consistently associated but displaced spatially more than 100 km from a deep-sea trench. Much of the eruptive activity is strongly explosive. Although some chains are strongly arcuate, others are linear. Adjacent to many island arcs in the western Pacific are back-arc basins floored by crustal spreading centers. Some arcs have associated nonvolcanic individual islands or island chains between the volcanic arc and trench, comprising uplifted, trench-accreted sediment.

    Oceanic lithosphere created at zones of plate divergence (mid-ocean ridges) is returned to the Earth’s interior at sites of plate convergence, specifically...

  112. ISLAND BIOGEOGRAPHY, THEORY OF
    (pp. 486-490)
    JOSÉ MARÍA FERNÁNDEZ-PALACIOS

    The theory of island biogeography, developed by Robert H. MacArthur and Edward O. Wilson successively in 1963 and 1967, argues for the existence of a dynamic balance in species richness on islands, as a function of the addition of species through the immigration of propagules to the island, plus any speciation within it (dictated by the degree of isolation from the mainland), and of species extinction from the island (dictated by island area). The result of these opposing forces, given enough time, is a dynamic equilibrium in which the species number remains approximately constant through time but species composition is...

  113. ISLAND FORMATION
    (pp. 490-492)
    PATRICK D. NUNN

    To understand how islands form, continental islands must be distinguished from oceanic islands, the former being pieces of continents with the connection submerged, the latter being younger islands that originated exclusively within the ocean basins. However they appear today—low or high, limestone or volcanic—all oceanic islands began life as ocean-floor volcanoes. Those that have not yet reached the ocean surface (and many never do so) are referred to as seamounts, whereas those that were once emergent but have since been submerged are often distinctively flat-topped and are called guyots.

    It comes as no surprise to learn that we...

  114. ISLAND RULE
    (pp. 492-496)
    SHAI MEIRI

    The island rule is a name given for the supposed tendency of small-bodied animals to evolve larger sizes on islands whereas large animals evolve toward relatively smaller body sizes. The evolutionary forces that drive the observed patterns and the circumstances under which the phenomenon is manifest are widely debated but are thought to include changes in resource abundance, lower interspecific competition, elevated levels of intraspecific competition, and reduced predation on islands.

    Anecdotal observation can lead to the conclusion that in many clades, island-dwelling species are characterized by extreme body sizes relative to their mainland counterparts, especially on large oceanic islands....

  115. JAPAN’S ISLANDS, BIOLOGY
    (pp. 497-500)
    LÁZARO M. ECHENIQUE-DIAZ, MASAKADO KAWATA and JUN YOKOYAMA

    The Japanese Archipelago consists of 4 major islands (Hokkaido, Honshu, Kyushu, and Shikoku) and 6848 smaller islands, arranged across 3500 km parallel to the eastern coast of the Asian continent, and separated from it by the Sea of Japan. Overall, the Japanese Archipelago extends over a latitudinal range of 25° and a longitudinal range of 31° Japan’s rich biota is reflective of the complex geological history of the archipelago and of the great diversity of climates it encompasses. It lies within two major biogeographic regions: the Palearctic and the Indo-Malay in faunal categories and the Holarctic and the Paleotropic in...

  116. JAPAN’S ISLANDS, GEOLOGY
    (pp. 500-506)
    S. MARUYAMA, S. YANAI, Y. ISOZAKI and D. HIRATA

    The Japanese islands are a bow-shaped chain of islands extending over 3000 km along the eastern margin of Asia. Four arcs—from north to south, the Kurile, Japan, Izu–Mariana, and Ryukyu arcs—are combined to form Japan. The Izu–Bonin arc extends south from the Japan arc (Fig. 1). The climate of Japanese islands is variable depending on latitude, ranging from snowy (from Hokkaido to northeastern Japan) to moderate (southwestern Japan) to subtropical (on the Ryukyu and Ogasawara arcs). One hundred and thirty million people live on the Japanese islands. Over 200 active volcanoes and their accompanying hot springs...

  117. JUAN FERNANDEZ ISLANDS
    (pp. 507-509)
    SIMON HABERLE

    The Juan Fernandez Islands are located in a warm temperate region of the far southeastern Pacific Ocean and consist of three large volcanic islands that harbor a flora of remarkably high endemism (about 67%). Historic human-induced changes to the island environments and their isolation from a continental landmass have contributed to degradation of the island biota, which is rapidly becoming one of the most threatened in the world.

    The Juan Fernandez archipelago is made up of three large volcanic islands—Isla Robinson Crusoe (or Masatierra; 33°37′ S, 78°51′ W; area 47.9 km²; elevation 915 m), Isla Alejandro Selkirk (or Masafuara;...

  118. KICK ’EM JENNY
    (pp. 510-512)
    JAN LINDSAY

    Kick ’em Jenny is a submarine basaltic volcano located approximately 8 km north of Grenada in the eastern Caribbean (Fig. 1). It is the most frequently active volcano in the Lesser Antilles island arc and the only known submarine volcano in the region.

    Kick ’em Jenny is a conical-shaped volcano that rises 1300 m from the sea floor. It is asymmetric, as it abuts the Grenadines shelf to the east. It has a summit crater about 320 m in diameter, and the highest point on the crater rim is about 180 m below sea level. There is an actively degassing...

  119. KĪPUKA
    (pp. 512-513)
    AMY G. VANDERGAST

    “Kīpuka” is one of several Hawaiian terms adopted by geologists to describe volcanic features, and is defined as a fragment of land surrounded by one or more younger lava flows (Fig. 1). Kīpuka are essentially habitat islands, and when present on islands themselves, kīpuka can be thought of as islands within islands. Kīpuka may play a unique role in shaping the ecology and evolutionary trajectories of species. Kīpuka undoubtedly act as refugia during flow events and provide source populations for colonists throughout ecosystem succession on new lava flows. As lava flows age, they are gradually recolonized by plant and animal...

  120. KOMODO DRAGONS
    (pp. 513-515)
    TIM JESSOP

    The Komodo dragon (Varanus komodoensis) is infamous for being the world’s largest lizard, reaching a maximum length of 3 m and a maximum body mass of up to 87 kg (Fig. 1). As adults, this monitor lizard is capable of killing and consuming mammals, including water buffalo (Bubalus bubalis), Timor deer (Cervus timorensis), and wild pigs (Sus scrofa), which coexist on five rugged islands in eastern Indonesia. Monitor lizards are monophyletic and comprise three clades; the Komodo dragon is assigned to the Indo-Australian lineage. Its closest sister species, as inferred from a mitochondrial gene tree, is the Eastern Australian lace...

  121. KON-TIKI
    (pp. 515-516)
    ROBERT C. SUGGS

    In 1947, the Norwegian explorer Thor Heyerdahl made a drift voyage of 101 days from Peru to Polynesia on the balsa-log raftKon-Tiki. Heyerdahl’s stated purpose was to prove his theory that Polynesia was settled from South America by light-skinned followers of a foreign god.

    Heyerdahl named theKon-Tikiafter the god he identified as “Kon-Tiki Viracocha.” This god was described as a bearded, white-skinned individual with reddish or blond hair and blue eyes who came to South America from across the Atlantic. Heyerdahl stated that this god remained in Peru for a time, before being driven out into the...

  122. KRAKATAU
    (pp. 517-520)
    ROBERT J. WHITTAKER

    The complete, or near-complete, sterilization of the Krakatau Islands in a devastating sequence of volcanic eruptions in 1883 provided a remarkable opportunity for natural scientists to monitor the processes and patterns of island recolonization and primary succession. Subsequent survey data, although intermittent in nature, extend to the present day and collectively (1) form a well-specified descriptive account of ecosystem development and (2) provide valuable opportunities for testing theories concerning the turnover and dynamics of insular systems. Most notably, Krakatau was the first case study system of colonization and turnover used by Robert H. MacArthur and Edward O. Wilson in evaluating...

  123. KURILE ISLANDS
    (pp. 520-525)
    ALEXANDER BELOUSOV, MARINA BELOUSOVA and THOMAS P. MILLER

    The Kurile (or Kuril) Islands are one of the last blank spots on the world map, and their very remoteness results in a uniquely pristine environment. The biodiversity of the islands is remarkable, ranging from broad-leaved sub-tropical forests with magnolia, ligneous lianas, and Kurile bamboo in the south to subarctic moss tundra, alder shrubs, and stunted birches in the north. The landscapes are impressive, combining rocky capes, heavy fogs, surrealistic volcanic cones, boiling crater lakes, and almost impenetrable giant grasses. The Kurile Islands have often been compared to the nearby Aleutian Islands, and with good reason in terms of geology,...

  124. LAKES, AS ISLANDS
    (pp. 526-531)
    SHELLEY ARNOTT

    Lakes are like islands; they are islands of water surrounded by a sea of land (Fig. 1). They have discrete boundaries (i.e., the water–land interface), yet there is some flow of materials, energy, and organisms from one system to the other. For example, whale carcasses occasionally wash ashore on islands and provide food energy for terrestrial-based organisms. Similarly, insects, mammals, and birds fall into lakes and are eaten by aquatic organisms. As on islands, organisms residing in lakes are spatially separated from other lakes by an inhospitable matrix. Organisms do not readily move from island to island or lake...

  125. LAND CRABS ON CHRISTMAS ISLAND
    (pp. 532-535)
    PETER GREEN

    Christmas Island (105°40′ E, 10°30′ S) is a small (135 km²), elevated (to 361 m above sea level) oceanic island lying 360 km south of Java in the northeastern Indian Ocean. It is an external territory of Australia, composed mostly of limestone and covered by rain forest where it has not been cleared for phosphate mining. Land crabs are ubiquitous components of the island’s terrestrial fauna. One species, the red land crabGecarcoidea natalis, determines the dynamics of seedling recruitment, a rare example of single-species dominance of this process in tropical rain forest.

    Air-breathing crabs characterize the terrestrial fauna on...

  126. LANDSLIDES
    (pp. 535-537)
    SIMON J. DAY

    Landslides take a wide variety of forms, but all involve the movement of rock, sediment, or soil under the influence of gravity. They may involve sliding of coherent rock or cohesive sediment masses on discrete surfaces or zones, but more commonly they involve rapid movement of fragmented material: The largest and most hazardous landslides are debris avalanches from volcanic islands.

    Mountainous islands at tectonic plate boundaries, such as Papua New Guinea and Taiwan, experience frequent landslides as a result of coastal erosion and cliff formation; rapid incision of rivers in response to tectonic uplift; and the proximity of the ocean...

  127. LAND SNAILS
    (pp. 537-542)
    BRENDEN S. HOLLAND

    Land snails are surprisingly adept at dispersing across vast stretches of open ocean, a fact supported by their presence on virtually all tropical and subtropical islands globally. Island snail radiations make fascinating subjects for the study of biogeography and diversification, as many archipelagoes have well-developed and diverse endemic snail faunas.

    Land snails are familiar molluscs with several characteristics that make them easily identifiable. They usually have paired eyes located at the tips of tentacles, a second pair of sensory tentacles, and a single, coiled shell into which the animals can generally withdraw their soft bodies for protection from predators and...

  128. LAVA AND ASH
    (pp. 542-544)
    KATHARINE V. CASHMAN

    Lava and ash are two different products of volcanic eruptions that cover the surfaces of volcanic islands. These two substrates have different volcanic origins and different physical properties, particularly with respect to their interaction with water (water transmission, storage, and susceptibility to erosion). The prevalence of one component or the other depends on the types of volcanic eruptions responsible for island formation. Eruption style, in turn, is determined primarily by the island’s location with respect to tectonic plates.

    Basaltic lava flows cover much of the surface area of volcanic islands that form over hotspots, such as Hawai‘i. In these settings,...

  129. LAVA TUBES
    (pp. 544-549)
    JIM KAUAHIKAUA, FRANK HOWARTH and KEN HON

    Lava tubes, originally called “pyroducts,” form within lava flows as thermally insulated conduits through which lava is carried away from a volcanic vent and supplied to an active lava flow. After draining and cooling, these same lava tubes, along with the right mixture of water, in the form of trapped humid air, and food, in the form of organic debris and root systems, can provide a very specialized ecological niche that requires organism adaptation. The opportunity to colonize these forbidding environments is responsible for some of the fastest evolutionary adaptation currently known.

    Volcanic islands, known to have lava tube caves,...

  130. LEMURS AND TARSIERS
    (pp. 549-553)
    ROBERT D. MARTIN

    Lemurs and tarsiers—two of the five main groups of living primates—are island inhabitants. Lemurs have undergone a major diversification on Madagascar, resulting in over 100 modern species (including 16 recently extinct representatives). Diversification of tarsiers on islands of Southeast Asia has been more modest, generating 17 modern species. However, 15 of those tarsier species are found on the relatively small island complex of Sulawesi, which is a “hotspot” for evolutionary divergence.

    The mammalian order Primates, to which we ourselves belong, contains five major groups: (1) lemurs; (2) lorisiforms (bushbabies and lorises); (3) tarsiers; (4) New World monkeys; and...

  131. LINE ISLANDS
    (pp. 553-558)
    CHRISTOPHER CHARLES and STUART SANDIN

    Oceanographers are often given to building transects, where contrasting properties can be observed within a relatively narrow geographic area. Such is the opportunity afforded by the Line Islands in the central tropical Pacific, an island chain that stretches from Johnston atoll in the north to the Tuamotu Islands in the south. The very name of the chain invites this transect approach, and, although the basic connotation of “The Line Islands” does not do justice to the complexity of its geological origin, the appellation does quite aptly describe the gradients in geographic properties manifested on the various islands.

    The atolls of...

  132. LIZARD RADIATIONS
    (pp. 558-564)
    MIGUEL VENCES

    Lizards belong to the clade Squamata, together with snakes, and among nonflying terrestrial vertebrates, they are the ones most commonly observed on islands. Lizards are characterized by a great facility in colonizing islands and adapting to novel ecological circumstances by changes in their morphology, physiology, and reproductive biology. They have consequently become an important model group for the inferential and experimental study of adaptive radiations.

    On major land-bridge islands with favorable climates (i.e., in the tropical, dry, and temperate zones) both lizards and snakes are commonly encountered, with snake species richness often being similar to lizard species richness. On 14...

  133. LOPHELIA OASES
    (pp. 564-567)
    SANDRA BROOKE

    The deep-water stony coralLophelia pertusa(Linnaeus 1758) creates extensive and complex structures on hard-bottomed areas in the deep sea, including continental shelf bedrock, lithified sediment mounds, volcanic basalt, and (microbially mediated) authigenic carbonate. Large colonies ofL. pertusahave abundant tangled branches that provide habitats for diverse and abundant associated communities. These long-lived and slow-growing coral ecosystems are currently under threat globally from negative human impact, and although some areas have been placed under protective legislation, continued international effort is needed to ensure the future of these valuable resources.

    There are several species of “framework-building” deep-water corals (Lophelia pertusa,...

  134. LORD HOWE ISLAND
    (pp. 568-572)
    CAROLE S. HICKMAN

    Lord Howe Island is the spectacular remnant of a large shield volcano that was active 7 million years ago in an isolated part of the southwestern Pacific Ocean between Australia and New Zealand. The high proportion of rare and endemic plants and animals, the rugged natural beauty of the landscape, and the occurrence of the southernmost coral reef in the world contribute to its status as a UNESCO World Heritage Site. The Permanent Park Preserve encompasses 75% of the island. Scientific studies dating from the 1850s have provided an unusually detailed documentation of natural history phenomena, making Lord Howe one...

  135. MACQUARIE, BIOLOGY
    (pp. 573-575)
    JENNY SCOTT

    Macquarie Island (54°30′ S, 158°56′ E) is a remote subantarctic island 1500 km south-southeast of Tasmania in the southern Pacific Ocean (Fig. 1). It has luxuriant herbaceous vegetation but no trees or shrubs, and it supports huge concentrations of seabirds and seals. As with all subantarctic islands, the terrestrial ecosystem of Macquarie evolved without mammals. Their introduction by humans has resulted in significant ecological impacts.

    Macquarie Island’s position just north of the Antarctic Polar Frontal Zone gives it a uniformly cool, wet, and windy climate (3.3–7.0 °C, 920 mm precipitation) with no permanent ice or snow. Its remote location...

  136. MACQUARIE, GEOLOGY
    (pp. 575-577)
    ARJAN DIJKSTRA

    Macquarie Island is a unique island of great geological importance, because it is the only locality in the world where a complete section of young ocean crust formed at a spreading center is exposed above sea level. It has thus become a type-locality for ocean crust and has played a major role in the development of theories of seafloor spreading, one of the key processes of plate tectonics. The island was put on the UNESCO World Heritage List in 1997 for this reason. The island also provides a key geological record of a spreading ridge system that became a convergent...

  137. MADAGASCAR
    (pp. 577-582)
    STEVEN M. GOODMAN

    As a result of its plant and animal endemism, nearly unparalleled in other portions of the world, and of the notable levels of threat associated with human activities, Madagascar has been designated as one of the priority biodiversity hotspots. This outstanding biological richness is a result of Madagascar’s long isolation, having been separated from Gondwana some 160 million years ago and having had no subsequent land connection. Furthermore, the island has notable topographic and geological complexity, providing different mechanisms for speciation. One remarkable aspect of this island nation is the number of new taxa being described each year. As it...

  138. MADEIRA ARCHIPELAGO
    (pp. 582-585)
    DORA AGUIN-POMBO and MIGUEL A. A. PINHEIRO DE CARVALHO

    Madeira is a small archipelago of volcanic origin with a highly diversified flora and fauna. A substantial amount of this diversity is harbored in the evergreen laurel forest, a formerly widespread type of vegetation that covered southern Europe and North Africa during the Tertiary period.

    The archipelago of Madeira is located in the Atlantic Ocean between 32 and 33° N and between 16 and 17° W, lying closer to Africa (~635 km) than to Europe (~794 km). Despite its size being less than 800 km², it comprises two inhabited islands, Madeira and Porto Santo; three islets of only 15 km²...

  139. MAKATEA ISLANDS
    (pp. 585-586)
    LUCIEN F. MONTAGGIONI

    The termmakatea, derived from Polynesian words (maka: slingstone;tea: white), relates to tropical Pacific islands possessing emergent (uplifted) limestones, mainly of coral reef origin and dissected by karst.

    Makatea islands possess a volcanic basement built by a number of different mechanisms affecting the Earth’s tectonic plates (hotspots, volcanism at or near divergent plate boundaries, arc volcanism at or near convergent plate boundaries). As the islands drowned due to crustal cooling, coral reefs developed around the volcanic cores. Locally, the volcanic pedestals were totally overtopped by reefal deposits. The time of deposition varies from site to site but was usually...

  140. MALDIVES
    (pp. 586-587)
    PAUL KENCH

    The Republic of Maldives consists of 21 atolls and four reef platforms that straddle the equator in the northern Indian Ocean. Comprising 2041 reefs and 1190 reef islands, the archipelago is globally unique in the reef structures it possesses and their mode of evolution. The reef islands are low-lying and small in size, which has generated wide-spread concern as to their vulnerability to future sea-level and climatic change.

    Located in the northern Indian Ocean, the Maldives archipelago is an 868-km-long network of coral reefs that extends from the northern atoll of Ihavandhippolhu (6°57′ N) to Addu Atoll (0°34′ S), just...

  141. MAMMAL RADIATIONS
    (pp. 588-591)
    LAWRENCE R. HEANEY and STEVEN M. GOODMAN

    Islands that have been isolated since their formation or for very long periods of time often have land mammal faunas that are made up largely or entirely of endemic species, and often these species are members of species-rich endemic clades. Though members of these endemic clades are each other’s closest relatives, they typically show highly diverse body size, morphology, behavior, and ecology. These constitute classic cases of adaptive radiation, in which local speciation has produced spectacular diversity.

    On very isolated and small islands, such as those in the central Pacific and southern Atlantic Oceans, native mammals are either absent or...

  142. MANGROVE ISLANDS
    (pp. 591-593)
    PETER SAENGER

    Mangrove islands are islands composed entirely or partially of mangrove vegetation and comprise microcosms of generally high productivity, high biodiversity, and structurally complex habitats in the nearshore environment. Such mangrove islands are largely confined to the tropics, with their latitudinal limits occurring in those regions where water temperatures never exceed 24 °C throughout the year. In comparison to shoreline mangroves, the vegetation of mangrove islands is subjected to much greater fluctuations in hydrological and meteorological conditions, resulting in its high dynamism and leading to its enhanced susceptibility to drastic change.

    Mangrove islands can be subdivided into two broad types: islands...

  143. MARIANAS, BIOLOGY
    (pp. 593-597)
    GORDON H. RODDA

    The Mariana archipelago is a line of small oceanic islands in the tropical northern Pacific Ocean about 1800 km east of the Philippine Islands. Because of its remoteness from Melanesian and Asian source areas, its small land area, its limited elevational range, and the sparse opportunities for faunal exchange among islands, the native biota of the Mariana Islands is relatively depauperate (species-poor), and native vertebrates are limited to species that can fly (birds, bats) or raft on floating vegetation and withstand contact with seawater (small lizards). Many of these vertebrates have been extirpated, and all but one of the Mariana...

  144. MARIANAS, GEOLOGY
    (pp. 598-603)
    FRANK A. TRUSDELL

    The Mariana Islands are the summits of a large volcanic mountain range that stretches 650 km from Guam to Uracas (Farallon de Pajaros; Fig. 1). The subaerial islands are but a small fraction of the mass, estimated at 0.5 to 1.5% of the volcanoes that form the Mariana Arc.

    The Northern Mariana volcanic islands form the upper 2–3 km of the East Mariana Ridge, which rises about 2–4 km above the ocean floor. To the east of the Mariana Ridge is the Mariana Trench, which is, at a depth of nearly 10 km, the deepest in the world....

  145. MARINE LAKES
    (pp. 603-607)
    MICHAEL N DAWSON, LAURA E. MARTIN, LORI J. BELL and SHARON PATRIS

    Marine lakes are bodies of seawater entirely surrounded by land. They come in a great variety of shapes, sizes, and distances from the “mainland” sea and can be described further in terms of their water-column characteristics and biotic complements, which may exhibit differences due, in part, to dissimilar physical connections with the sea. Marine lakes are “habitat islands” that exhibit the biogeographic, ecological, and evolutionary characteristics of “true islands” (with varying degrees of isolation), mainland fragments, or otherwise patchily distributed habitat.

    The distribution of marine lakes is poorly documented. They are mentioned, often incidentally, in literature for tourists or on...

  146. MARINE PROTECTED AREAS
    (pp. 607-610)
    ALAN M. FRIEDLANDER

    Marine protected areas (MPAs) are any intertidal or subtidal areas, together with their associated flora, fauna, and historical and cultural features, that have been set aside by law or other effective means to protect part or all of the designated environments. Marine reserves are a more restrictive subset of MPAs and are defined as areas permanently and completely protected from extractive harvest and other major human uses.

    As a result of overfishing and overall degradation of marine ecosystems, marine protected areas (MPAs) have increasingly been proposed as an ecosystem-based management tool to conserve biodiversity and manage fisheries. Closing certain areas...

  147. MARSHALL ISLANDS
    (pp. 610-612)
    NANCY VANDER VELDE

    The loosely strung double archipelagoes of Ratak and Rālik, with their 29 atolls and five solitary coral islands, make up what is now known as the Marshall Islands. Marine life associated with these north central Pacific islands is rich and varied. Terrestrial environments range from lush forests and inland mangrove ponds to dry shrublands, with a relatively limited diversity of plant and animal species. All the atolls and islands are low in elevation. Some of the northern atolls were used for nuclear tests, the impact of which is still being studied.

    The atolls and islands of the Marshall Islands were...

  148. MASCARENE ISLANDS, BIOLOGY
    (pp. 612-619)
    CHRISTOPHE THÉBAUD, BEN H. WARREN, DOMINIQUE STRASBERG and ANTHONY CHEKE

    The Mascarenes are an island group lying near the Tropic of Capricorn in the southwestern Indian Ocean ~700 km east of Madagascar. This archipelago comprises three high volcanic islands (Réunion, Mauritius, Rodrigues), scattered along a ~600 km west-east axis, and a group of small coralline islands (Cargados Carajos Shoals) ~400 km to the north of Mauritius, which sit upon a submarine bank of volcanic origin that extends a further 700 km or more to the northeast. The Mascarene Islands have an extraordinary status among islands: Mauritius was the former home of the dodo, the universal symbol of human-caused species extinction...

  149. MASCARENE ISLANDS, GEOLOGY
    (pp. 620-622)
    ROBERT A. DUNCAN

    The west-central Indian Ocean volcanic islands of Reunion, Mauritius, and Rodrigues are collectively known as the Mascarene Islands. They are volcanoes related to an age-progressive trend of north-to-south volcanic activity that includes the coral-capped Mascarene plateau and the Chagos-Maldive-Laccadive ridge, extending northward to the Deccan flood basalts of western India (Fig. 1). The origin and distribution of these elevated features, rising from ocean floor depths of 4–5 km, are thought to be the result of plate motions over the Reunion hotspot, a persistent upper mantle melting anomaly maintained by focused mantle upwelling. The primary evidence for this idea is...

  150. MEDITERRANEAN REGION
    (pp. 622-629)
    JOHN WAINWRIGHT

    Islands make up a significant component of the Mediterranean coastline, with about 19,000 km of length compared to the total of some 46,000 km. However, there are only five large islands—Sicily, Sardinia, Cyprus, Corsica, and Crete, in decreasing order—but numerous groups of smaller islands (Fig. 1). This article describes the groups and individual islands following a clockwise direction from the northwest.

    The Mediterranean Sea has an area of ~2.54 million km², with an average water depth of about 1500 m and a total volume of about 3.7 million km³. It stretches from about 45°42′ N in the northern...

  151. METAPOPULATIONS
    (pp. 629-631)
    DAG ØYSTEIN HJERMANN

    Metapopulations are “populations of populations”—collections of island populations bound loosely together by occasional migration between the islands. Metapopulation theory has been applied to terrestrial environments (where the “islands” are patches of habitat in an “ocean” of unsuitable habitat) as well as to real island archipelagoes. The theory is especially useful in conservation biology.

    A basic concept of MacArthur and Wilson’s theory of island biogeography was that the collection of species found on an island is dynamic. The metapopulation theory, first used by Richard Levins in 1970, shares this dynamic view of animal populations. In contrast to MacArthur and Wilson’s...

  152. MIDWAY
    (pp. 631-633)
    ELIZABETH FLINT

    Midway atoll (28°15′ N, 177°20′ W) consists of three sandy islets (Sand Island: 4.56 km², Eastern Island: 1.36 km², and Spit Island: 0.05 km²), for a total of 5.98 km² in terrestrial area, lying within a large, elliptical barrier reef measuring approximately 8 km in diameter (Fig. 1). Although geographically part of the Hawaiian archipelago, Midway is not part of the State of Hawaii and is an unincorporated territory of the United States.

    The climate of Midway is influenced by the marine tropical or marine Pacific air masses, depending upon the season. During the summer, the Pacific high pressure system...

  153. MISSIONARIES, EFFECTS OF
    (pp. 633-638)
    ALAN I. KAPLAN and VINCENT H. RESH

    Missionaries have gone to islands to convert local populations away from indigenous religions for millennia. They have been successful because of geographical isolation and cultural aspects of island life, as well as internal and external political influences. The activities of missionaries on islands have resulted in improvements in health, agricultural development, and education but also have brought about drastic cultural changes. Missionaries often had positive influences on island peoples’ lives but, having the range of human frailties, sometimes also did irreparable harm.

    Islands have been the recipients of a great deal of missionary activity relative to the size of the...

  154. MOA
    (pp. 638-641)
    ALLAN J. BAKER

    Isolated island archipelagoes with ecologically diverse habitats can be veritable laboratories of evolution for many organisms. Some of the most spectacular examples involve colonizing species of birds, such as Darwin’s finches in the Galápagos Islands and Hawaiian honeycreepers, both of which have undergone adaptive radiations primarily involving incredible differences in bill morphology. Another equally spectacular but less wellknown adaptive radiation occurred in the now extinct moa on the two larger islands of New Zealand, the North and South Islands. Moa were giants of the bird world; species varied in body mass from 20 to 250 kg, with the largest genus...

  155. MOTU
    (pp. 641-642)
    FRANCIS J. MURPHY

    A motu is a small island, made entirely of coral reef sediment, which forms on top of a barrier reef (Fig. 1). These islands are variably capable of supporting vegetation, seabird colonies, and human settlements, but because of their low elevation and small size, they are also highly susceptible to the effects of major storms and changes in sea level.

    Motuis a Polynesian-language term that means “small island” (the plural is alsomotu), and it is most commonly used for all reef islands associated with high islands, almost-atolls, and atolls. In the scientific classification of reef islands, a distinction...

  156. NEW CALEDONIA, BIOLOGY
    (pp. 643-645)
    JÉRÔME MURIENNE

    Because of its extremely diverse biology, New Caledonia is one of few islands to be designated a biodiversity hotspot. The long isolation of the territory (since the breakup of Gondwana 80 million years ago), in conjunction with its climatic stability, was often proposed as an explanation for its outstanding biodiversity. Recent evolutionary studies are more in accordance with submersion of the territory from 65 to 45 million years ago, establishing a new paradigm for the origin of biodiversity in this island.

    New Caledonia is a Melanesian archipelago comprising two sets of islands (Fig. 1). The first includes the main island...

  157. NEW CALEDONIA, GEOLOGY
    (pp. 645-648)
    TIMOTHY J. RAWLING

    The New Caledonia archipelago is a group of islands that form the emergent northern part of the Norfolk Ridge in the Southwest Pacific Ocean. The archipelago consists of six major islands as well as numerous smaller islands. The closest neighboring island group is Vanuatu, 500 km to the northeast, while New Zealand and Australia are situated 1500 km to the south and west, respectively. The New Caledonian territorial boundaries are approximately between latitude 18° and 23° S and longitude 158° and 172° E, and the land area of the archipelago is in the order of 18,600 km².

    The largest island...

  158. NEWFOUNDLAND
    (pp. 649-652)
    HAROLD WILLIAMS

    The island of Newfoundland is a textbook example of a collisional geologic mountain belt. It formed through the opening and closing of an ancient Iapetus Ocean, which preceded the modern North Atlantic. The cycle of opening and closing lasted for about 300 million years. The major geologic divisions of Newfoundland represent the margins and vestiges of Iapetus.

    The island of Newfoundland forms the northeast extremity of the Appalachian Mountain Belt, or Appalachian Orogen, in eastern North America (Fig. 1). The northeast coastline of the island displays a complete cross section of the Appalachians in superb wave-washed cliff exposures. Since the...

  159. NEW GUINEA, BIOLOGY
    (pp. 652-659)
    ALLEN ALLISON

    New Guinea, the world’s largest and highest tropical island, was one of the last parts of the globe to be explored, earning it the nickname “the last unknown.” Although many of its species have yet to be scientifically named, we do know that is inhabited by an extraordinarily rich assemblage of plants and animals, derived from both Southeast Asia and Australia, with diversity exceeding that of the much larger Australian continent and rivaling that of the Amazon Basin. Overall it has ~8% of the world’s biota. At least 70% of species are endemic.

    In this treatment, New Guinea includes the...

  160. NEW GUINEA, GEOLOGY
    (pp. 659-665)
    HUGH L. DAVIES

    The island of New Guinea is made up of elements of Australian and Pacific geology. It is in a dynamic part of the world and has been the subject of benchmark studies into plate tectonics, ophiolite, rifting of continents, Quaternary sea levels, and other fields. Because the geological history of the island is relatively short, it is more readily deciphered than for older regions of Earth’s crust.

    New Guinea lies across the northern margin of Australia. It is the second largest island in the world, 2200 km long and up to 750 km wide, and one of the most mountainous,...

  161. NEW ZEALAND, BIOLOGY
    (pp. 665-673)
    STEVEN A. TREWICK and MARY MORGAN-RICHARDS

    New Zealand, spanning more than 1400 km of latitude on the southwest edge of the Pacific Ocean, supports a distinct assemblage of plant and animal groups. Species-level endemism in the wet temperate forests and alpine habitats is high; however, compared to many other oceanic islands, species diversity is not. New Zealand is a small part of a large continent, Zealandia, that sank beneath the surface of the sea after separation from Gondwanaland and is thus often considered a continental island. Whether any of the New Zealand biota originated in Zealandia is uncertain, but a number of animals that lack close...

  162. NEW ZEALAND, GEOLOGY
    (pp. 673-680)
    HAMISH CAMPBELL and CHARLES A. LANDIS

    In geological terms, New Zealand may be regarded as an emergent portion of a sunken continent. This is unusual globally; the Kerguelen Plateau may be the only other modern example of a large tract of submerged continental crust, or sunken continent. The New Zealand land area represents just 7% of a much larger area of submerged continental crust referred to as Zealandia. New Zealand owes its existence as land to tectonic collision along a northeast-southwest-oriented segment of the plate boundary separating the Australian Plate (to the west) from the Pacific Plate (to the east), a process that has been especially...

  163. NUCLEAR BOMB TESTING
    (pp. 680-685)
    EDWARD L. WINTERER

    Nuclear bomb testing by the United States began just two years after the end of World War II and continued intermittently until late 1962, running up a total of 105 tests of fission (A-bomb) and fusion (H-bomb) weapons, all of them in the atmosphere or in shallow lagoon waters. The tests were conducted not only to evaluate successive bomb designs but also to observe the effects of nuclear explosions on ships and crews.

    Islanders were evacuated from Bikini atoll (now Pikini) successively to a series of other atolls, where they fared poorly because of poor environments for fishing and growing...

  164. OASES
    (pp. 686-689)
    SLAHEDDINE SELMI and THIERRY BOULINIER

    The term “oasis” is often taken in its metaphorical and very broad sense: a spot of life within an inhospitable environment. In that way, it has repeatedly been used to designate patches of vegetation in less-vegetated and dry landscapes, isolated ice-free areas in Antarctica, isolated life-rich areas in marine ecosystems, and every other kind of isolated habitat. Even though these systems are comparable in that they are isolated and different from their surroundings, their structure, origin, and evolution, as well as the factors affecting their dynamics, are widely different. Oases are more classically defined as relatively more fertile areas in...

  165. OCEANIC ISLANDS
    (pp. 689-696)
    PATRICK D. NUNN

    Those of us who live close to the edges of the world’s continents are likely to be familiar with islands, often as places for recreation or retreat. In the past, they were sometimes places of refuge for people or other biota escaping continental calamities ranging from warfare to ice advance. In a geological sense, such islands are commonly slivers of continent, their connections drowned by the high-sea-level conditions in which we live today. Oceanic islands are quite different, often smaller and more remote, and to find them, the continental dweller generally has to travel much farther offshore, into the hearts...

  166. ORCHIDS
    (pp. 696-700)
    DAVID L. ROBERTS and RICHARD M. BATEMAN

    Assisted by their dustlike seeds, orchids are among the first plant families to colonize islands, often speciating into the many unexploited niches on newly formed or newly disturbed islands. Reduced (or at least temporarily reduced) competition on some islands may allow more radical evolutionary shifts, as well as the establishment of new relationships between an orchid lineage and its necessary partners—animals for pollination and mycorrhizal fungi for germination and nutrition. Furthermore, the tendency of orchids to be pollinator-limited, and thus to occur as small populations, has resulted in orchids frequently evolving through founder effect and genetic drift.

    Orchids are...

  167. ORGANIC FALLS ON THE OCEAN FLOOR
    (pp. 700-701)
    CRAIG R. SMITH

    Organic falls are large parcels of organic matter (e.g., dead fish, marine mammal carcasses, wood and other vascular plant debris, masses of macroalgae) that sink largely intact to the sea floor. Because most of the sea floor underlies deep water and is food-limited (fed by a diffuse rain of organic material from surface waters), large organic falls on the deep-sea floor create food-rich islands in an energy-poor desert. Suites of deep-sea species rapidly consume a broad range of organic-fall types, causing these food-rich islands to be relatively ephemeral (i.e., lasting for days to decades).

    The rates and patterns of exploitation...

  168. PACIFIC REGION
    (pp. 702-715)
    ANTHONY A. P. KOPPERS

    The Pacific Region is extraordinary in many aspects. It is the largest ocean on Earth, harbors the deepest trenches, has the highest abundance of islands, and underneath its sea surface it encompasses the largest tectonic plate on Earth. Its enormity is emphasized by the fact that Christmas Island in the center of the Pacific Ocean lies more than 8,000 km away from any continent. As a whole the islands in the Pacific Region are referred to as Oceania, the tenth continent on Earth. Inherent to their remoteness and because of the wide variety of island types, the Pacific Islands have...

  169. PALAU
    (pp. 715-717)
    ALAN R. OLSEN

    Located in the western equatorial Pacific Ocean, Palau is the westernmost group of islands in Micronesia. The archipelago rests on the eastern edge of the continental shelf of the Philippine Plate, approximately 800 km east of Mindanao. Palau is a mixture of old volcanic islands, raised limestone islands, coralline platform islands, and atolls representing an exposed crest of the now-dormant southern section of the Palau–Kyushu Ridge. It is estimated that the volcanic islands emerged approximately 30 million years ago during the late Oligocene.

    Palau, approximately 7º30′ N latitude and 134º35′ E longitude, extends northeast to southwest for 700 km,...

  170. PANTEPUI
    (pp. 717-720)
    VALENTÍ RULL

    Pantepui (pan, Greek for “all,” andtepui, South American indigenous name for “table mountains”) is a discontinuous biogeographical entity shaped by the assemblage of the flat-topped summits of the Guayana (northern South America) table mountains, or Guayana Highlands (Figs. 1 and 2), above 1500 m in altitude. These summits are isolated from each other and from the surrounding lowlands by spectacular vertical cliffs, and they hold a singular biota with unique adaptations and amazing levels of biodiversity and endemism. The origin of such biotic patterns is a still-unresolved evolutionary enigma.

    The indigenous (Pemón) wordtepui, meaning “stone bud,” has been...

  171. PEOPLING THE PACIFIC
    (pp. 720-723)
    PATRICK V. KIRCH

    The islands of the Pacific Ocean were settled by humans in two major episodes. The earliest phase began in the Late Pleistocene, at least 40,000 years ago, and involved the movement of hunting-and-gathering populations into Near Oceania. The second major phase commenced about 4000 years ago and involved the diaspora of the Austronesian-language speakers into Remote Oceania, as well as into the Indian Ocean as far as Madagascar. The most isolated islands and archipelagoes of Remote Oceania, including Hawai‘i, Easter Island (Rapa Nui), and New Zealand (Aotearoa), were settled by Polynesians between AD 800 and 1200.

    The Pacific Islands, or...

  172. PHILIPPINES, BIOLOGY
    (pp. 723-732)
    RAFE M. BROWN and ARVIN C. DIESMOS

    The Philippines (Fig. 1) is one of the Earth’s most spectacular island archipelagoes. The country spans the Asian–Australian faunal zone interface at the sharpest biotic demarcation (Wallace’s Line) on the planet. Although collectively comprising a land mass approximately the size of the U.S. state of Arizona, the Philippines is a complex archipelago with more than 7100 distinct islands. Geographically situated on the edge of multiple colliding tectonic plates, the Philippines has an ancient and complex geological history that has only recently come to light. Ancient land mass movements, environmental gradients along steep volcanic slopes, and sea level–induced alterations...

  173. PHILIPPINES, GEOLOGY
    (pp. 732-738)
    GRACIANO YUMUL JR., CARLA DIMALANTA, KARLO QUEAÑO and EDANJARLO MARQUEZ

    Island arc systems such as the Philippines are produced through accretion brought about by collision of geologic blocks, resulting in volcanism and emplacement of crust and mantle fragments on land. The various igneous, sedimentary, and metamorphic rock types in island arcs reflect the complex processes involved in their generation and evolution. Island arc-related processes involve interactions of geological features (e.g., trenches, volcanoes, and faults) that result in specific tectonic evolution, geologic hazards, and mineral deposits.

    The Philippines, an arc system lying off the Asian land mass, is trapped at the margins of the Eurasian–Sundaland and the Philippine Sea Plates....

  174. PHOSPHATE ISLANDS
    (pp. 738-740)
    JAMES R. HEIN

    Phosphate islands host deposits of phosphate rock (also called phosphorite) of sufficient quantity and quality to be economically mined. Most of the phosphate rock deposits were derived from bird droppings (guano). The phosphate rock was mined at various times in the past, but the only extant mine in the Pacific is on the island of Nauru in the west equatorial Pacific. The most common phosphate minerals in insular phosphate rocks are composed of calcium (Ca2+) and phosphate (PO₄3-), combined with charge-balancing anions such as fluoride (F⁻), chloride (Cl⁻), and hydroxide (OH⁻). Calcium phosphates are used predominantly in agriculture as fertilizer,...

  175. PIGS AND GOATS
    (pp. 741-743)
    ELIZABETH MATISOO-SMITH

    Pigs (Sus scrofa) and goats (Capra hircus) were two important domesticated animals taken to islands by early agriculturalists. Later introductions of these animals by European explorers and sailors, who often left them on islands as provisions for passing ships or shipwreck survivors, further extended their island distributions. Unfortunately, the impact of these animals on island ecosystems has been significant. In recent years eradication measures have been undertaken to remove these invasive species and restore the native island habitats they destroyed.

    Pigs and goats belong to the order Artiodactyla. Both species are omnivores and particularly adaptable, which no doubt was one...

  176. PITCAIRN
    (pp. 744-747)
    NAOMI KINGSTON and NOELEEN SMYTH

    Pitcairn Island is one of four islands in the Pitcairn group, the most easterly island group in Polynesia: Pitcairn, a relatively young, high volcanic island; Henderson, an atoll uplifted by the eruption of Pitcairn; and two non-uplifted atolls, Ducie and Oeno. The group is extremely remote, separated from both New Zealand and South America by over 4500 km; from Easter Island, the nearest neighbor to the east, by 1570 km; and from the Gambier Islands to the west by 450 km. The isolation of Pitcairn makes it of equal interest to those studying the island’s biota and its origins, those...

  177. PLANT DISEASE
    (pp. 747-752)
    ULLA CARLSSON-GRANÉR, LARS ERICSON and BARBARA E. GILES

    Diseases can increase mortality, decrease reproduction and growth of plants, and ultimately influence the sizes and genetic structures of populations and the species composition in plant communities. Plant populations situated on small and distant islands may more easily escape diseases than those on the mainland, where host and pathogen populations lie in close proximity. However, if pathogens spread to island populations that have previously evolved in absence of diseases, their effects may be severe. Studies of patterns of disease in insular systems have shown that the ages and sizes of plant populations and the distance between islands affect disease spread...

  178. PLATE TECTONICS
    (pp. 752-755)
    ROGER C. SEARLE

    Plate tectonics was developed in the 1960s and 1970s as the unifying, global theory of the Earth sciences. It assumes that the outer surface of the Earth is made up of thin, brittle tectonic plates, which have rigid interiors and interact only at their edges, where their relative motions produce earthquakes and volcanoes. By measuring the relative velocities of the plates in a finite number of places, their motions across the world and over the geological past can be computed using relatively simple geometric techniques. The assumption of rigid, undeformable plates breaks down to some extent in some continental areas...

  179. POCKET BASINS AND DEEP-SEA SPECIATION
    (pp. 755-757)
    BRUCE H. ROBISON and WILLIAM M. HAMNER

    Isolation is an important agent in the evolution of new species. When two populations of a single species become sufficiently isolated that there is no exchange of genetic material, then random genetic mutations and genetic drift over time will eventually render them distinct from each other. Thereafter, if the environmental conditions that affect these two populations begin to differ, genetic separation (speciation) can proceed even faster. Island chains at and near the sea surface and pocket basins in the deep seafloor provide the isolation necessary for speciation in the ocean.

    Scientists often rely on the manipulation of natural systems or...

  180. POLYNESIAN VOYAGING
    (pp. 758-761)
    ATHOLL ANDERSON

    Polynesia consists of Samoa and Tonga (West Polynesia), settled initially by Lapita voyagers about 3000 years ago, and the dispersed archipelagoes of East Polynesia, especially Hawaii, French Polynesia, Easter Island, Cook Islands, and New Zealand, colonized 1100–700 years ago (Fig. 1). The term “Polynesian voyaging” refers to the means by which island colonization was effected and the extent to which interaction occurred between distant islands. One extreme of opinion envisages exclusively accidental colonization by one-way voyaging that precluded development of long-range interaction, while at the other extreme, purposeful and navigated voyaging within a strategic system of colonization, multiple contact,...

  181. POPULAR CULTURE, ISLANDS IN
    (pp. 761-765)
    VINCENT H. RESH and JONATHAN P. RESH

    Popular culture is the culture of the people. It includes the fashions, movies, television shows, advertising, and even video games that are easily accessible to individuals with a wide variety of social backgrounds. Emphasis in popular culture is on instant accessibility; no prior or profound knowledge is required. The use of islands in popular culture is an excellent example of how media can use strong images and perceptions to influence people’s taste and behavior.

    Island images are generally positive—they emphasize sensuality, escape, solitude, seduction, and self-sufficiency. However, negative images are there as well—islands also can be lonely, inhospitable,...

  182. POPULATION GENETICS, ISLAND MODELS IN
    (pp. 766-767)
    JEFFREY D. LOZIER

    Species are rarely spatially continuous or homogenous in their distributions; more often they are geographically subdivided into local subpopulations, within which individuals frequently interact but between which interactions are less common. Such population structure is often complex and can alter the way in which evolutionary forces (gene flow, genetic drift, and natural selection) act in nature. Island models and their variants provide a useful framework in which to investigate genetic variation and its potential ecological and evolutionary consequences in subdivided populations.

    In many scientific disciplines, researchers are interested in measuring demographic parameters for the organisms under study, including numbers of...

  183. PRISONS AND PENAL SETTLEMENTS
    (pp. 767-771)
    EPHRAIM COHEN

    Prisons are institutions in which people are confined and deprived of a large range of liberties. The obvious parallel between islands and prisons resides in isolation, whether from mainland or from society. The more distant an island is from the mainland, and the deeper, colder, stormier, and more infested with predators (e.g., sharks) its surrounding waters are, the more effective it is as a prison. Opportunities to escape from such islands are drastically reduced or even completely eliminated. Whereas prisons on the mainland are usually cell prisons, on islands convicts were not always confined but rather held in camps. On...

  184. RADIATION ZONE
    (pp. 772-775)
    KOSTAS A. TRIANTIS and ROBERT J. WHITTAKER

    Species richness on island systems is a function of colonization, speciation, and extinction. In island faunas and floras, there exist radiation zones, in which phylogenesis (including by adaptive radiation) increases with distance from the major source region. Within-island speciation and within-archipelago speciation (sometimes termed simply archipelago radiation) can thus be major contributors to species richness.

    In their seminal bookThe Theory of Island Biogeography, MacArthur and Wilson (1967) wrote, “In equilibrial biotas … the following prediction is possible: adaptive radiation will increase with distance from the major source region and, after corrections for area and climate, reach a maximum on...

  185. RAFTING
    (pp. 775-778)
    CHRISTOPHE ABEGG

    Natural rafting is the rare occurrence in which animals or plants of any kind succeed in crossing a sea strait using tree parts and vegetation. Although rafting has understandably been more often regarded as a means of dispersal for marine plants and animals, it also happens to terrestrial plants and non-volant animals. It is thought that animals are launched by chance from riversides (at any time for reptiles or small mammals but probably at night and during a flood for macaques; Fig. 1), or along the coast (for any animal whenever a tsunami strikes). Once the plant or animal is...

  186. REEF ECOLOGY AND CONSERVATION
    (pp. 779-785)
    ROBERT H. RICHMOND, WILLY KOSTKA and NOAH IDECHONG

    Coral reefs are the most biologically diverse marine ecosystems on Earth, rivaling terrestrial tropical rain forests. They are ecologically, economically, and culturally valuable resources that provide billions of dollars in goods and services to millions of people. An estimated 30% of the world’s reefs have been substantially degraded during the past few decades, with predictions that nearly 60% are in jeopardy of being lost by the year 2050 if present trends continue. Anthropogenic stressors including overfishing, sedimentation, pollution, eutrophication, and warming tied to global climate change are responsible for losses and are reducing natural resilience and the potential for recovery....

  187. REFUGIA
    (pp. 785-787)
    ANGUS DAVISON

    A refugium is a geographic area in which organisms survive during adverse conditions. Although the term is most frequently applied to the glacial–interglacial cycles of the Pleistocene, species that are endangered as a result of human actions or ongoing climate change are restricted to modern-day “refugia.” One common feature of refugia is that they may contain the greatest of relictual biodiversity, meaning that they merit special conservation attention.

    The impact of the Pleistocene glacial–interglacial cycles on the flora and fauna of high latitudes has been well characterized, especially in North America and Europe. In these regions, large tracts...

  188. RELAXATION
    (pp. 787-788)
    KENNETH J. FEELEY

    Relaxation is the process by which species are lost from an island following a disturbance event that increases the rate of local extinction, decreases the rate of colonization, or both. The disturbance is typically a decrease in area or increase in isolation, but it may alternatively be a change in habitat quality or any other disturbance event that decreases the number of species that the island can support at equilibrium (Fig. 1). Relaxation is most commonly referred to in the setting of continental islands or mainland habitat fragments (e.g., sky islands). In both of these settings, habitat that was originally...

  189. RESEARCH STATIONS
    (pp. 788-792)
    NEIL DAVIES

    Most islands have limited indigenous resources (human, financial, and physical) to support research, and they rely on importing the people (skills) and equipment needed for scientific studies. Some island research stations are little more than specialized guest houses, but others rival the most advanced mainland laboratories. Where a station falls along this spectrum depends on a number of factors, including (1) the scientific interest of the location, (2) its socioeconomic context, and (3) its potential to support educational and public service activities. All of these are being radically transformed by (4) new information and communication technologies.

    Studies at research stations...

  190. RODENTS
    (pp. 792-796)
    DAVID TOWNS

    Islands throughout the world have been modified by introduced rodents. A few highly destructive species have been deliberately released to establish a fur industry. Mice and four species of rats have reached islands as passengers during exploration, warfare, and commerce. These have become the perfect invasive species, able to spread over wide distances and with significant ecological effects wherever they colonize.

    There are more species of rodents (around 2000) than of any other group of mammals. Isolation and extraordinary dispersal ability have led to considerable evolutionary radiation on less remote islands and continental fragments, with distinctive faunas in Madagascar, Sri...

  191. ROTTNEST ISLAND
    (pp. 796-798)
    ANNE BREARLEY

    Rottnest Island, 1900 ha in area and located 17 km off the coast of Perth, is an iconic holiday destination for many Western Australians and popular tourist venue for 500,000 visitors each year. Limestone buildings from the colonial period in the 1800s still form the heart of the settlement. Motor vehicles are used only for maintaining services, with visitors riding bicycles, walking, or using buses to explore the island. The scenic bays with clear turquoise waters are ideal for swimming, and the colorful diverse marine life is of great fascination to all (Fig. 1).

    Willem de Vlamingh, a member of...

  192. SAMOA, BIOLOGY
    (pp. 799-802)
    A. C. MEDEIROS

    The Samoan archipelago is a volcanic chain of nine main inhabited islands, high islets, and low coral islands located about 13°–15° south of the equator in the central South Pacific (though disjunct Swains Island is 11° S). The archipelago is divided into two political entities: Western Samoa (officially called Independent Samoa or Samoa) to the west and American Samoa (an unincorporated territory of the United States) to the east. Western Samoa consists of Savai‘i (1820 km² area; 1860 m elevation) and ‘Upolu (1110 km²; 1100 m), the fifth and eighth largest islands of the tropical Pacific, and a number...

  193. SAMOA, GEOLOGY
    (pp. 802-808)
    JAMES H. NATLAND

    The Samoan Islands are at the eastern end of a chain of volcanoes, most of them submerged, and very near the southwestern edge of the main Pacific Basin at the Tonga Trench (Fig. 1). The islands proper span a distance of about 400 km along a trend of about 290°, but the entire chain, in the form of shallow banks and submarine volcanic pinnacles, extends to the west for about another 1200 km. The islands resemble the Hawaiian Islands in many respects, but some features of them are distinct. The principal difference results from being near the Tonga Trench rather...

  194. SÃO TOMÉ, PRÍNCIPE, AND ANNOBON
    (pp. 808-811)
    D. JAMES HARRIS

    The islands of the Gulf of Guinea are part of one of the world’s biodiversity hotspots. Part of a volcanic chain that includes Mount Cameroon on the continent, the islands are Bioko, São Tomé, Príncipe, and Annobon. Although Bioko was connected to the continent during the last interglacial period, São Tomé, Príncipe, and Annobon are all surrounded by deep-sea trenches and are thus true “oceanic islands.” These islands are striking centers of endemism. In contrast to most oceanic islands, where habitat loss is probably the chief conservation concern, in these islands control of introduced species may play a more critical...

  195. SEABIRDS
    (pp. 811-815)
    MARK J. RAUZON and SHEILA CONANT

    From the nearshore waters to the open ocean, seabirds are the most conspicuous component of marine systems. Soaring on brisk winds, floating buoyantly amidst cresting waves or flying underwater, this varied group of birds has adapted to the demanding life at sea, utilizing the marine environment to feed and returning to land, primarily islands, to breed.

    There are approximately 350 species of seabirds in seven orders. Here, we highlight four orders most characteristic of insular systems: Sphenisciformes (penguins), comprising 16–18 species; Procellariiformes (albatross, shearwaters [Fig. 1], petrels, and storm petrels), with over 100 species; Pelicaniformes (pelicans, cormorants, boobies [Fig....

  196. SEA-LEVEL CHANGE
    (pp. 815-818)
    W. H. BERGER

    Sea level has been rising around the world for the last hundred years. For the second half of the last century, the overall rate of the global rise is between 1.5 and 2 mm per year, according to various compilations. When projecting this same rise forward in time, the total rise by the end of the century turns out to be between 15 cm and 20 cm, an estimate that agrees with the latest assessment offered by the Intergovernmental Panel on Climate Change (IPCC) of the World Meteorological Organisation (WMO) and the United Nations Environment Programme (UNEP). It is distinctly...

  197. SEAMOUNTS, BIOLOGY
    (pp. 818-821)
    MALCOLM CLARK

    Seamounts occur in all oceans of the world, from the tropics to the poles, and cover depth ranges from near the surface to the abyss. They provide a wide variety of habitat types for a huge range of animals and often feature high levels of biodiversity and abundance. This can make them important components of oceanic ecosystems, yet also the target of commercial exploitation.

    Seamounts have three important characteristics that distinguish them from the surrounding deep-sea habitat. First, they are “islands” of shallow sea floor, surrounded by the deep ocean, and they provide a range of depths for different communities....

  198. SEAMOUNTS, GEOLOGY
    (pp. 821-825)
    PAUL WESSEL

    Seamounts are traditionally defined as undersea mountains whose summits rise more than 1000 m above the sea floor; however, modern studies describe seamounts down to several tens of meters in height. They generally exhibit a conical shape with a circular, elliptical, or more elongated base. Seamounts are some of the most ubiquitous landforms on Earth and are present in uneven proportions in all ocean basins. Being volcanic in nature, seamounts are mostly found on oceanic crust and to a much lesser extent on extended continental crust. They are generated near mid-ocean spreading ridges, in plate interiors over upwelling plumes (hotspots),...

  199. SEXUAL SELECTION
    (pp. 825-829)
    KENNETH Y. KANESHIRO and RICHARD T. LAPOINT

    Sexual selection is defined as the differential mating success among individuals of the same sex, males in most cases. Sexual selection is viewed as a dynamic, frequency-dependent process, a driver for evolutionary change, and a synergist for the formation of new species.

    Because of their isolated nature, islands are among the best places for investigating evolutionary processes, and research on specific groups of organisms that evolved on islands, or island-like habitats, has begun to shed light on processes by which species diversify and originate, processes such as sexual selection. For example, the Hawaiian Archipelago is often considered to be the...

  200. SEYCHELLES
    (pp. 829-833)
    JUSTIN GERLACH

    The Republic of Seychelles comprises 115 islands spread over 1.3 million km² of the western Indian Ocean. The majority of these are small and uninhabited. Of the Seychelles’ 80,000 human inhabitants, 90% live on the largest island, Mahé (153 km²), and 7% on the next largest, Praslin (28 km²). The islands can be divided into two groups: the northern islands (the granitic islands and the coral cays of Bird and Denis) and the southern coral islands (Fig. 1).

    The granitic islands are mostly composed of Precambrian granite (750 million years old) and represent fragments of the ancient supercontinent of Gondwana....

  201. SHIPWRECKS
    (pp. 833-835)
    JAMES HAYWARD

    Island life and exploration have always necessitated the use of ships and other vessels, be it for transportation, for exploration, for commerce, or for recreation. From rafts and canoes, to sailing ships and steamers, to modern cruise ships and tankers, there have always been some of these vessels that failed to make it safely to their destination. Every shipwreck, whether one unnamed and unknown or an icon in world history such as theTitanic, has the potential to make an impact on island life. While each shipwreck may have a variety of consequences, the most common and most influential include...

  202. SILVERSWORDS
    (pp. 835-839)
    BRUCE G. BALDWIN

    Silverswords belong to an ecologically diverse lineage of endemic Hawaiian woody and semi-woody members of the sunflower family (Compositae) collectively known as the Hawaiian silversword alliance (31 species inArgyroxiphium,Dubautia, andWilkesia). True silverswords and greenswords (Argyroxiphium; five species), named for their narrow, sword-shaped leaves (silvery-hairy in silverswords), are spectacular rosette plants of alpine cinder slopes, forest edges, mesic scrub, and bogs on Maui and Hawai‘i (Fig. 1). These famous, young-island endemics are closely related to the bizarre, fibrous-leaved rosette plants inWilkesia(two species), found on generally dry or exposed slopes of western Kaua‘i, and to trees, shrubs,...

  203. SKY ISLANDS
    (pp. 839-843)
    JOHN E. MCCORMACK, HUATENG HUANG and L. LACEY KNOWLES

    Sky islands are high-elevation habitats that are geographically subdivided and isolated among different mountain ranges (Fig. 1). Because of differences in climatic history and dispersal dynamics, the ecological and evolutionary processes and patterns characterizing sky islands may not always parallel those for traditional oceanic archipelago systems. Nevertheless, like their oceanic counterparts, sky islands are generators of diversity over multiple spatial and temporal scales and offer considerable potential for investigating how different evolutionary processes such as natural selection and genetic drift lead to species formation.

    The term “sky islands” was originally coined by Weldon Heald in his writings on the mountains...

  204. SNAKES
    (pp. 843-846)
    GORDON H. RODDA

    Snakes (3000+ spp.) are a highly specialized and successful limbless form of lizard. Their low metabolic rate combined with jaw anatomy that accommodates the ingestion of relatively prodigious meals allows snakes the energetic option of long fasts between large meals, permitting them to rely on infrequent food sources such as annually nesting birds. Avian and mammalian predators require more continuous food sources and therefore cannot survive on islands lacking year-round prey. Accordingly, snakes are the top predator on many islands, especially land-bridge islands that experience pulses of visiting birds. However, snakes are rare on most oceanic islands because they are...

  205. SOCOTRA ARCHIPELAGO
    (pp. 846-851)
    KAY VAN DAMME

    The Socotra Archipelago (Yemen), situated in the Arabian Sea, consists of four main islands on an ancient microplate. Socotra, the largest island, is known as the “Galápagos of the Indian Ocean” because of its high biodiversity in both terrestrial and marine realms. A long period of isolation from the Afro-Arabian mainland and a significant geological diversity have resulted in a high endemism with remarkable relicts.

    The Socotra Archipelago is located in the Arabian Sea, situated 380 km southeast from the coast of Yemen, to which it politically belongs, and about 100 km east from the Horn of Africa (Cape Guardafui,...

  206. SOLOMON ISLANDS, BIOLOGY
    (pp. 851-854)
    ORLO C. STEELE

    Within the South Pacific Island nation of the Solomon Islands there are hundreds of islands, ranging from large high volcanic islands to low atolls, with a total of 4023 km of coastline and an economic exclusive zone of 1,340,000 km². The biodiversity of the Solomon Islands appears to be the richest among the Pacific Island nations, with the exception of Papua New Guinea. However, the collection of specimens and field observations has been limited, and new species are discovered with each new inventory.

    The Solomon Islands extend 1450 km in a southeast direction from 5° S and 152° E to...

  207. SOLOMON ISLANDS, GEOLOGY
    (pp. 854-857)
    HUGH L. DAVIES

    The Solomon Islands are part of the Outer Melanesian Arc, a discontinuous chain of islands that stretches from the Bismarck Archipelago in the northwest to Fiji and Tonga in the southeast. The islands lie within latitudes 5–12° S.

    The Solomon Islands comprise more than 1000 generally mountainous islands that are distributed in two geographic areas. Most islands are in the western and central area, where they form a 1200-km-long northwest-trending double chain, founded upon a basement ridge (Fig. 1). These islands include Bougainville and Buka, which are politically a part of Papua New Guinea. Islands of the Santa Cruz...

  208. SPECIES-AREA RELATIONSHIP
    (pp. 857-861)
    DAVID A. SPILLER and THOMAS W. SCHOENER

    For over a century, ecologists have been captivated by the tendency for number of species within a taxonomic group to increase with island area. This “species–area relationship” has been found for a broad range of organisms in numerous archipelagoes around the world. A partial list of studies demonstrating the relationship includes land plants on the Galápagos (Fig. 1) and Aleutian Islands; insects on the Tuscan Islands and on subantarctic islands; reptiles on islands in the Gulf of California and in the West Indies; birds on the Canary, Solomon, and Aegean Islands; and mammals on islands in the Philippines and...

  209. SPIDERS
    (pp. 861-865)
    MIQUEL A. ARNEDO

    The ability to produce silk is a distinctive feature of spiders. Silk-mediated airborne dispersal has allowed spiders to colonize even the most remote archipelagoes. Spiders on islands have served as models for the study of the evolutionary and ecological underpinnings of biodiversity. Because of their generalist predatory habits, introduced spiders may pose a serious threat to islands’ native fauna.

    Spiders (order Araneae) comprise a megadiverse group of arthropods that includes close to 40,000 species distributed in 109 families. The origin of spiders can be traced back to the Devonian, about 400 million years ago, representing some of the earliest evidence...

  210. SPITSBERGEN
    (pp. 865-866)
    MARIA WŁODARSKA-KOWALCZUK

    Spitsbergen is the largest island (38,000 km²) of the Svalbard archipelago located at the northeastern edge of the Barents Sea shelf.

    Despite its high Arctic location (74 to 81º N), the island experiences relatively mild weather conditions, with average air temperatures ranging from –12 ºC in February to 5 ºC in July. Heat is transported to these high latitudes by the Atlantic waters of the west Spitsbergen current, a distant branch of the Gulf Stream. The Greenland Sea waters off the west coast are ice-free throughout most of the year. The Barents Sea polar water masses occurring north and east...

  211. SRI LANKA
    (pp. 866-870)
    COLIN GROVES and KELUM MANAMENDRA-ARACHCHI

    Sri Lanka is, for its size, the most biologically diverse of all islands. It has three distinctive climatic zones, each with its own characteristic fauna, two of which show only the most distant biological affinities with nearby India. A tropical (5°55′–9°51′ N) island nation, Sri Lanka is classed as part of South Asia and is separated from southern India by the narrow (20 km wide) Palk Strait. It is teardrop shaped, with a north–south length of 432 km and a maximum east–west width of 224km. The total area is 65,610 km².

    Sri Lanka is geologically part of...

  212. ST. HELENA
    (pp. 870-873)
    PHILIP ASHMOLE and MYRTLE ASHMOLE

    St. Helena—one of the most isolated inhabited islands in the world—lies at latitude 15°58’ S and longitude 5°43’ W, about 800 km east of the Mid-Atlantic Ridge in the southern Atlantic Ocean. The island played a significant part in the development of biological concepts such as endemism, extinction, and the origins of insular biota. Less than a decade after publication of Charles Darwin’sThe Origin of Species, the botanist Joseph Hooker used his firsthand knowledge of St. Helena in a seminal lecture on insular floras to the British Association for the Advancement of Science, and the chapter on...

  213. STICKLEBACKS
    (pp. 873-877)
    MICHAEL A. BELL

    The stickleback fish family (Gasterosteidae) comprises five major subgroups (genera), three of which are primitively marine but commonly colonize freshwater (Fig. 1). The habitats of these freshwater colonists contrast sharply with the marine environment from which they came, and their descendants rapidly evolve behavioral, physiological, and morphological traits that adapt them to diverse freshwater environments. Glaciation and isostatic depression eliminated freshwater fishes over wide areas of the Holarctic. When those areas became exposed, sticklebacks and other fishes that move readily through the ocean but tolerate freshwater quickly colonized these newly formed, fishfree, freshwater habitats. Consequently, freshwater stickleback populations are common...

  214. SUCCESSION
    (pp. 877-879)
    BEATRIJS BOSSUYT

    Succession consists of the often-predictable series of changes in an ecological community over time after a disturbance. These changes occur through colonization and extinction of species. Primary succession involves the assembly of a plant community on a newly formed substrate, whereas secondary succession indicates community changes after a disturbance that has destroyed the vegetation but left the soil to a large extent intact. During primary succession, species accumulate in the plant community through dispersal, environmental selection, and biotic interactions, resulting in an increase of species richness with time. On islands, both dispersal limitations and environmental selection differ from those on...

  215. SURF IN THE TROPICS
    (pp. 879-883)
    GRAHAM SYMONDS and THOMAS C. LIPPMANN

    The wave climate around islands is highly variable in space and time as a result of the level of exposure to incident waves and the frequency of local and distant storm events. The magnitude of the incident waves affects the distribution of benthic communities such as algae, corals, and fish assemblages, as well as the distribution of sediment and the accretion and erosion of shorelines. Topographic effects often provide waves highly sought by surfers. Waves breaking on coral reefs around islands can have a significant impact on sea level and mean currents in an otherwise sheltered lagoon, flushing water, nutrients,...

  216. SURTSEY
    (pp. 883-888)
    STURLA FRIDRIKSSON

    Off the southern shore of Iceland in the North Atlantic Ocean is a group of 14 islands and a number of skerries called Vestmannaeyjar or the Westman Islands. The largest of these is Heimaey at 11.6 km², the only populated member in the archipelago. The youngest and the outermost island is Surtsey. It was formed during a volcanic eruption that started on November 14, 1963.

    That morning a fishing boat was situated some 20 km southwest off Heimaey. At dawn the captain saw a column of smoke coming out of the sea and realized that a volcanic eruption had started....

  217. SUSTAINABILITY
    (pp. 888-896)
    R. R. THAMAN

    Sustainability, or “sustainable development,” is the ability of island nations or communities to acquire the income needed to purchase material and non-material goods from the modern cash economy that are needed to make life healthier, safer, more productive, and more enjoyable, but, at the same time, doing so without destroying the local natural and cultural capital needed for the material and cultural survival of future generations. Sustainability is about balancing these two, often conflicting, objectives: achieving the right balance between cash and subsistence economies, between self-reliance and dependency. For many traditional and indigenous peoples, sustainability is not so much about...

  218. TAIWAN, BIOLOGY
    (pp. 897-902)
    MAN-MIAO YANG and KUANG-YING HUANG

    Taiwan, an island of approximately 36,000 km², is situated in the western Pacific Ocean and separated from China by the Taiwan Strait. It is also known as Formosa (Fig. 1), meaning “the beautiful island,” a name given to it by Portuguese mariners who encountered it in the sixteenth century. Around the main island of Taiwan, there are more than 80 smaller islands, including the granite-origin continental islands, volcanic oceanic islands, cubic basalt-formed Pescadores (Penghu archipelago) (Fig. 2A), and coral-reef based islands (e.g., Pratas atoll [Fig. 2B]). This article focuses on the main island of Taiwan.

    Lying directly in the center...

  219. TAIWAN, GEOLOGY
    (pp. 902-904)
    YUE-GAU CHEN

    Taiwan, located in the western margin of the Pacific with a center at 24° N, 121° E, is an olive-shaped island with a length and width of ~400 km and 200 km, respectively. The highest mountain peak, Jade Mountain, rises ~4000 m above sea level. Approximately two-thirds of the island’s area is characterized by mountains, hills, and tablelands. Only the remaining one-third is settlement-suitable plain, an area that is mainly distributed along the western coast.

    Taiwan is dominated by mountain ranges because of its tectonic setting. Based on geologic and seismologic lines of evidence, Taiwan has been defined as one...

  220. TASMANIA
    (pp. 904-909)
    ALASTAIR M. M. RICHARDSON

    Tasmania is a medium-sized continental island lying southeast of the Australian mainland. It is topographically diverse, largely forested, and supports a number of relictual and endemic species. It has been occupied by aboriginal people for at least 30,000 years and by Europeans for just over 200 years.

    Tasmania is a continental island of about 68,400 km², lying between latitudes 40 and 43° S, about 200 km off the coast of southeastern Australia, from which it is separated by Bass Strait. Several substantial offshore islands are associated with the mainland of Tasmania, notably Bruny and Maria Islands off the east coast,...

  221. TATOOSH
    (pp. 909-912)
    EGBERT GILES LEIGH JR. and ROBERT T. PAINE

    Tatoosh (Fig. 1) is a set of islets covering 17 to 18 ha at 48°24´ N, 124°44´ W, 0.6 km off Cape Flattery, the northwest tip of the Olympic Peninsula. A lighthouse on the largest islet marks the southern lip of the strait of Juan de Fuca, which leads from the Pacific Ocean to Seattle and Vancouver. These islets’ rocky shores support a luxuriant community of intertidal organisms. Research there by Robert Paine and his students and colleagues has revealed many of the factors that govern what lives where on rocky shores, and has shed light on other, very different...

  222. TAXON CYCLE
    (pp. 912-913)
    MANDY L. HEDDLE

    The taxon cycle was originally conceived to explain species distributions on islands where, within a particular species complex, some species are widespread, abundant, and found in coastal habitats, whereas others are fragmented, rare, and occupy montane habitats. The mechanism for the cycle is driven by new colonists (early-stage species) that establish populations on coastal, marginal habitats, outcompeting established populations, which experience shifts in ecological adaptations as they are forced toward more interior habitats. As more colonists arrive, older taxa (late-stage species) become further specialized for particular ecological conditions and occupy increasingly interior habitats, such that their populations become fragmented and...

  223. TIDES
    (pp. 914-917)
    MARLENE NOBLE

    Tidal sea-level fluctuations, which are fundamentally caused by the gravitational attractions between the rotating Earth and the moving positions of the sun and the moon, not only cause the sea level to regularly cover and expose beaches over most of the Earth but also transport water, suspended material, nutrients, larvae, and debris onto or off of the adjacent landmass. Because of their regularity, these tidal fluctuations are well known at any particular location not only by humans, who predict the depth of water in a harbor in order to dock a ship, but also by the many living organisms in...

  224. TIERRA DEL FUEGO
    (pp. 917-918)
    MATTHEW J. JAMES and JOHN M. WORAM

    Tierra del Fuego is the extensive archipelago of large and small islands at the southern tip of South America, separated from the mainland by the Strait of Magellan. Its total area is 73,746 km², two-thirds of which is owned by Chile, one-third by Argentina. The largest island within the archipelago is Isla Grande de Tierra del Fuego (Fig. 1).

    The archipelago is further divided by the Beagle Channel running along the southern coast of Isla Grande. Along the Argentine territory, it forms the border with the Chilean islands to the South. The Chilean territory contains Cape Horn and False Cape...

  225. TONGA
    (pp. 918-921)
    DONALD R. DRAKE

    Tonga is an archipelago of small, tropical, Pacific islands consisting of limestone or volcanic rock. The natural vegetation is tropical rain forest, and the native vertebrate fauna includes bats, birds, and lizards. The terrestrial environment has been strongly modified by humans, resulting in deforestation, animal extinctions, and invasion by alien species, although significant remnants of the native biota still exist.

    The Kingdom of Tonga is a South Pacific nation consisting of about 700 km² of land divided among 170 scattered islands (Fig. 1). The archipelago lies just west of where the Pacific tectonic plate is being subducted beneath the Indian-Australian...

  226. TORTOISES
    (pp. 921-926)
    CHARLES R. CRUMLY

    Size change is one of the most common patterns of evolution on islands—dwarfism in some cases and gigantism in others. Land tortoises become giants. Three independently evolved lineages of giant tortoises survived until historic times (Figs. 1–4). The Galápagos Islands tortoise populations include a dozen or so species, some extinct and others with small but recovering populations. Two other lineages of giants evolved on different island groups of the Indian Ocean. Only one species of these two lineages survives, mostly on the isolated atoll of Aldabra. Land tortoises represent, in the public conscience, both the pattern of insular...

  227. TRINIDAD AND TOBAGO
    (pp. 926-929)
    CHRISTOPHER K. STARR

    Trinidad and Tobago are two small islands with a combined land area of about 5100 km², lying just off the northeast edge of the South American continent (Fig. 1) at 10°02´–11°21´ N and 60°31´–61°55´ W. Southwest Trinidad is separated from the mainland by an 11-km strait, whereas in the northwest there are steppingstone islands between Trinidad and the mainland. Tobago is separated from Trinidad by a 36-km strait. Trinidad’s Northern Range and Tobago are eastern extensions of Venezuela’s long Coastal Range.

    The islands are characterized by moderate topography—maximum elevation 940 m for Trinidad, 576 m for Tobago—...

  228. TRISTAN DA CUNHA AND GOUGH ISLAND
    (pp. 929-932)
    PETER G. RYAN

    Renowned for supporting the most remote human community, the Tristan archipelago and Gough Island are small, cool-temperate, volcanic islands in the central South Atlantic. The islands range in age from 0.2 to 18 million years, resulting in a wide diversity of topography. Their isolation has led to high levels of endemism among the biota. Despite being discovered more than 500 years ago, Tristan was settled only in the early 1800s and is the only permanently inhabited island. The other islands have been relatively little impacted by humans. Currently, the main threats to native species are introduced rodents as well as...

  229. TSUNAMIS
    (pp. 933-936)
    EMILE A. OKAL

    Tsunamis are gravitational oscillations of the entire body of water of an ocean basin, following a disruption in the bottom (or exceptionally the surface) of the ocean. They differ from more conventional swells by their much longer periods (typically from 10 min to 1 hr) and relatively faster speeds over deep ocean basins (typically 220 m/s, or the speed of a modern jetliner). Tsunamis are capable of exporting death and destruction across entire ocean basins, their propagation being limited only by continental masses.

    Although tsunamis were once called “tidal waves,” they are not caused by tides. Most tsunamis are generated...

  230. VANCOUVER
    (pp. 937-939)
    MARTIN L. CODY

    Vancouver Island, 48–51° N latitude, is the largest island off the Pacific coast of North America, part of the western Canadian province of British Columbia, and the location of its provincial capital Victoria. The island is renowned for its soaring mountains, abundant lakes and waterfalls, spectacular coastal scenery, and imposing coniferous forests especially along the cooler and wetter western coastlines. It measures 450 km on its long axis (Cape Scott in the northwest to Victoria in the southeast), about four times its maximum width, with an area of 32,000 km²; the 2200-m Mt. Golden Hinde, in Strathcona Provincial Park,...

  231. VANUATU
    (pp. 939-941)
    JÉRÔME MUNZINGER

    Vanuatu, an archipelago in the southwestern Pacific, is famous for its active volcanoes, both emergent and under the ocean’s surface. Largely because of its relatively modest terrestrial biodiversity, Vanuatu was recently included in the newly expanded East Melanesian Islands hotspot. The archipelago’s recent volcanic origin, the result of interaction between the subducting Australian plate and the Pacific plate, is often proposed as an explanation of its relative low level of distinctiveness. However, Vanuatu has also been poorly investigated, and some islands have never been explored; thus, it may provide surprises in the future.

    Vanuatu, officially the Republic of Vanuatu, is...

  232. VEGETATION
    (pp. 941-947)
    DIETER MUELLER-DOMBOIS

    Vegetation is, simply, the plant cover of landscapes. It can be subdivided into plant communities on the basis of differences in structure (such as forest, shrubland, savanna, open forest, closed forest, summer deciduous forest, etc.), species dominance and composition (for example, eucalyptus forest, pine forest, softwood/hardwood forest, etc.). Vegetation is the most obvious and important biological component of terrestrial ecosystems and provides basic environmental services: Through its role as an absorber of carbon dioxide, an oxygen emitter, and a primary producer, it provides for life in terrestrial environments; it acts as an air filter or air conditioner in the Earth’s...

  233. VICARIANCE
    (pp. 947-950)
    MICHAEL HEADS

    In plants and animals, closely related species and groups of species often occur in different areas, and this pattern is called vicariance. Its origin can be explained by a process, also termed vicariance, in which a widespread common ancestor differentiates and breaks up, more or less in situ, into related descendants. For example, consider a variety of plant or animal that is found only on (i.e., is endemic to) a certain island. It may have its closest relative on a nearby mainland. Isolation and differentiation of the island population from the mainland one could have arisen by vicariance if the...

  234. VOLCANIC ISLANDS
    (pp. 950-954)
    JOHN M. SINTON

    In the broadest sense, volcanic islands include all islands that form by volcanic processes, even those islands that represent ancient volcanic terranes that have been tectonically exposed, such as Gorgona Island offshore of Colombia or Macquarie Island in the southwestern Pacific. It also should be noted that most atolls represent a calcareous carapace surmounting oceanic volcanoes, the volcanic part of which has subsided below sea level, a concept originally proposed by Charles Darwin and subsequently confirmed by drilling through shallow carbonate atolls into the underlying volcanoes of the Hawaiian and Tuamotu island chains. However, attention here will be restricted to...

  235. VOYAGE OF THE BEAGLE
    (pp. 954-961)
    JERE H. LIPPS

    HMSBeagle, with Capt. Robert FitzRoy and young Charles Darwin aboard, left the island of Britain for hydrographic surveying, particularly in the Southern Hemisphere, on December 27, 1831, on a voyage spanning nearly five years, to October 2, 1836. Over 40 islands were visited or closely approached, including the Galápagos Islands, which Darwin later made famous. Darwin observed and recorded information about the geology, biology, and people of the many places he visited, which was then used in his later books and papers.

    Robert FitzRoy had been an officer on the earlier voyage of theBeagle(1828–1831) to southern...

  236. WALLACE, ALFRED RUSSEL
    (pp. 962-967)
    ELIN CLARIDGE

    Alfred Russel Wallace (1823–1913) is best known as the co-author of the theory of evolution by natural selection, with Charles Darwin. However, he was also an influential British scientist and social thinker of his time. As a young man, he traveled extensively in the Amazon River basin, and then in the Malay Archipelago, working as a professional collector, naturalist, and explorer. Besides his contributions to the development of evolutionary theory, Wallace is considered a founding father of the field of biogeography. He published articles and books covering a wide array of topics in both the natural and social sciences....

  237. WALLACE’S LINE AND OTHER BIOGEOGRAPHIC BOUNDARIES
    (pp. 967-971)
    JEREMY D. HOLLOWAY

    Wallace’s Line represents the first attempt to establish a boundary between two major biotic regions of the world within an entirely archipelagic context. A prerequisite is the recognition of such biotic regions: gross areas that support distinctive but generally distributed assemblages of plants and animals. These regions are all continent-based, with climate being a secondary factor in the Northern Hemisphere: temperate versus tropical. A regional boundary must represent the most significant transition between two regions in terms of losses and gains of components. This transition should also be relatively abrupt: a discontinuity.

    The eighteenth century saw a significant increase in...

  238. WARMING ISLAND
    (pp. 971-973)
    KURT M. CUFFEY

    Warming Island, situated at the north end of Liverpool Land in eastern Greenland (71°29’ N; 21°51’ W), is not particularly significant as a physical feature. Instead this island is noteworthy because of its connection to two major themes: the formation of new islands and the impacts of climate warming on glacial landscapes. Warming Island became an island only recently—between 2002 and 2005—when the glacial isthmus connecting it to the mainland was destroyed by melt and disintegration of ice, a consequence of climate warming (Fig. 1).

    Quaternary glaciation has sculpted the island into three narrow parallel ridges, whose sides...

  239. WHALE FALLS
    (pp. 973-975)
    AMY BACO

    “Whale fall” is the general term for a sunken whale carcass resting on the sea floor. Whale falls pass through a series of successional stages ranging from scavenging of soft tissue through to a highly diverse chemoautotrophic assemblage, fueled by sulfides from the anaerobic breakdown of lipids contained in the whale bones. Whale falls have species overlap with hydrothermal vents and cold seeps and thus have been hypothesized to have played a role in the dispersal and evolution of vent and seep fauna. In addition to these shared species, whale fall communities have components of endemic and specialized fauna that...

  240. WHALES AND WHALING
    (pp. 975-979)
    JOE ROMAN

    Whaling has impacted all species of great whales. It has also changed island ecosystems and cultures, spread invasive species and disease, and brought some island species, such as the Galápagos tortoise, to the brink of extinction. As hunting has declined, whale watching has risen as an important economic activity on many islands.

    There are currently about 80 recognized species of cetaceans, divided into two suborders, the Mysticeti, or filterfeeding baleen whales, and the Odontoceti, or toothed whales, a category that includes dolphins, porpoises, and sperm whales. The great whales, a group based on the cultural history of whaling rather than...

  241. WIZARD ISLAND
    (pp. 979-981)
    DAVID W. RAMSEY

    Rising steeply above the water like a sorcerer’s pointed hat, Wizard Island is the most prominent and recognizable feature in Crater Lake, Crater Lake National Park, Oregon. Crater Lake, the deepest lake in the United States and the seventh deepest lake in the world (594 m depth relative to the shoreline), partially fills the caldera that formed approximately 7700 years ago by the eruption and subsequent collapse of an approximately 3700-m volcano called Mount Mazama. Since the climactic eruption of Mount Mazama, there have been several less violent, smaller post-caldera eruptions within the caldera itself. Wizard Island is one of...

  242. ZANZIBAR
    (pp. 982-986)
    N. D. BURGESS and R. A. D. BURGESS

    The tropical archipelago of Zanzibar comprises two large islands and 53 smaller ones. It is located in the Indian Ocean at longitude 39° E and latitude 6° S. The larger island has traditionally been referred to as Zanzibar Island but is known locally as Unguja. It is 35 km offshore of the Tanzanian mainland, from which it is separated by the Zanzibar Channel, and it is distinct from its sister island of Pemba, which is located further north across the deep-water Pemba Channel (Fig. 1). These islands are a part of a global center of species diversity in the terrestrial...

  243. GLOSSARY
    (pp. 987-1018)
  244. INDEX
    (pp. 1019-1075)
  245. [Map]
    (pp. 1076-1077)