Pollination and Floral Ecology

Pollination and Floral Ecology

Pat Willmer
Copyright Date: 2011
Pages: 828
https://www.jstor.org/stable/j.ctt7rn7p
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  • Book Info
    Pollination and Floral Ecology
    Book Description:

    Pollination and Floral Ecologyis the most comprehensive single-volume reference to all aspects of pollination biology--and the first fully up-to-date resource of its kind to appear in decades. This beautifully illustrated book describes how flowers use colors, shapes, and scents to advertise themselves; how they offer pollen and nectar as rewards; and how they share complex interactions with beetles, birds, bats, bees, and other creatures. The ecology of these interactions is covered in depth, including the timing and patterning of flowering, competition among flowering plants to attract certain visitors and deter others, and the many ways plants and animals can cheat each other.

    Pollination and Floral Ecologypays special attention to the prevalence of specialization and generalization in animal-flower interactions, and examines how a lack of distinction between casual visitors and true pollinators can produce misleading conclusions about flower evolution and animal-flower mutualism. This one-of-a-kind reference also gives insights into the vital pollination services that animals provide to crops and native flora, and sets these issues in the context of today's global pollination crisis.

    Provides the most up-to-date resource on pollination and floral ecologyDescribes flower advertising features and rewards, foraging and learning by flower-visiting animals, behaviors of generalist and specialist pollinators--and moreExamines the ecology and evolution of animal-flower interactions, from the molecular to macroevolutionary scaleFeatures hundreds of color and black-and-white illustrations

    eISBN: 978-1-4008-3894-3
    Subjects: Ecology & Evolutionary Biology, Zoology, Biological Sciences, Botany & Plant Sciences

Table of Contents

  1. Front Matter
    (pp. i-iv)
  2. Table of Contents
    (pp. v-vi)
  3. PREFACE
    (pp. vii-viii)
    Pat Willmer
  4. ACKNOWLEDGMENTS
    (pp. ix-x)
  5. PART I ESSENTIALS OF FLOWER DESIGN AND FUNCTION
    • Chapter 1 WHY POLLINATION IS INTERESTING
      (pp. 3-10)

      The flowering plants (angiosperms) account for about one in six of all described species on earth and provide the most obvious visual feature of life on this planet. In the terrestrial environment, their interactions with other living organisms are dominant factors in community structure and function; they underpin all nutrient and energy cycles by providing food for a vast range of animal herbivores, and the majority of them use animal pollinators to achieve reproduction. Most of the routine “work” of a plant is carried out by roots and leaves, but it is the flowers that take on the crucial role...

    • Chapter 2 FLORAL DESIGN AND FUNCTION
      (pp. 11-54)

      Flowers are essentially the containers for a plant’s sex organs, but they must perform several interrelated functions. Most obviously, and taking center stage here, they make and mature the gametes and then dispense the male gametes in such a way that they will be transported to another appropriate flower in the process of pollination, leading to fusion with female gametes. However, the flower must also be structured so that it protects the crucial sex organs through pollination and seed set, both from the environment (excessive rain or drought, freezing, heat load in full sun or during flash fires, physical damage...

    • Chapter 3 POLLINATION, MATING, AND REPRODUCTION IN PLANTS
      (pp. 55-87)

      Reproduction in plants, as in most organisms, can be either sexual or asexual, but the generation of new variants (which is the underlying necessity for adaptation to new or changing conditions and for evolutionary change) requires that at some point in the life cycle sexual reproduction occurs. Diploid cells must undergo meiotic division to produce haploid cells (gametes) with half the normal chromosome number, and a gamete from one individual must then interact with another gamete (preferably but not necessarily from another individual) to effect fertilization and so reinstate the diploid state, resulting in an embryo that grows into the...

    • Chapter 4 EVOLUTION OF FLOWERS, POLLINATION, AND PLANT DIVERSITY
      (pp. 88-102)

      Animals of various kinds must have been interacting with green plants—both for shelter and to find food—almost as soon as land plants evolved. Any foliage would provide some shelter, both in terms of alleviating the microclimatic conditions and by offering some possibility of hiding from predators. It would also offer decomposing plant material as potential food, where microorganisms had already softened and partially digested the plant walls. However, eating fresh, green plant tissue was a later development, as true herbivory is a difficult skill that requires modifications to the gut to extract the maximum nutrition from rather poor-quality...

  6. PART II FLORAL ADVERTISEMENTS AND FLORAL REWARDS
    • Chapter 5 ADVERTISEMENTS 1: VISUAL SIGNALS AND FLORAL COLOR
      (pp. 105-133)

      Visual attraction by flowers is substantially related to flower shape and size, and the basic aspects of these were covered in chapter 2. But above all, for most visitors, color and color patterns are attractive. Trichromatic color vision occurs in many terrestrial animals, and in the evolution of insects it certainly predates the flower-visiting habit. Undoubtedly most of today’s key pollinating taxa have good color vision, and flowers should have been selected to interact with their visitors’ visual abilities. So it is not surprising that plants use color signals to make their flowers conspicuous in a mainly “green” world. Since...

    • Chapter 6 ADVERTISEMENTS 2: OLFACTORY SIGNALS
      (pp. 134-153)

      The previous chapter concentrated on visual signaling by flowers, but it is usually not appropriate to look only at flower color and shape as attractants, given the abilities of most flower visitors, and insects in particular, to detect and respond to scents or odors as well; the latter are often the major component of floral attraction to visiting animals.

      Floral scents mostly result from the production of small amounts of simple volatile organic compounds. The molecular size of these components largely determines their volatility, and hence the distance they will travel from the plant over a given time span. In...

    • Chapter 7 REWARDS 1: THE BIOLOGY OF POLLEN
      (pp. 154-189)

      A pollen grain contains the male gamete of the angiosperm plant and is thus the equivalent of a spore in many other plants. In essence, the structure of a pollen grain is adapted to protect and nourish the male gamete during its maturation and subsequent transit between plants, and then to ensure that one of its nuclei reaches and fertilizes an ovule within another plant. The grain must alight on an appropriate stigma and germinate, then develop a pollen tube down through the style along which the nucleus can travel so that the nucleus passes down to the ovary at...

    • Chapter 8 REWARDS 2: THE BIOLOGY OF NECTAR
      (pp. 190-220)

      Nectar is the main secondary floral reward in an evolutionary sense, appearing on the scene probably in the late Cretaceous in angiosperms, later than pollen. But it has very often become the primary offering of a flower (chapter 4), thereby protecting the plant’s investment in the reproductively useful pollen. As a commodity, nectar is easy for plants to produce and easy for animals to handle, its sugars being simple to metabolize and thus to use as a readily available fuel for an animal’s activities. The general properties of nectar are usefully reviewed by de la Barrera and Nobel (2004) and...

    • Chapter 9 OTHER FLORAL REWARDS
      (pp. 221-233)

      Occasionally flowers offer neither pollen nor nectar as a foodstuff to their visitors but instead yield other rewards; or they may offer these as “extras” in addition to some pollen. This chapter reviews these possibilities, considering a range of oils, waxes, scents, and resins (on which topics Simpson and Neff [1981, 1983] provided earlier reviews), as well as some less tangible rewards that can be obtained from flower visits.

      First described in detail by Vogel (1969), fatty oils as an offering in flowers are now known from at least 80 genera across several families (table 9.1) and from nearly 1%...

    • Chapter 10 REWARDS AND COSTS: THE ENVIRONMENTAL ECONOMICS OF POLLINATION
      (pp. 234-258)

      Pollination is usually thought of as a mutualism, of benefit to both partners, each of which gains in fitness. In such a relationship, both should be trying to maximize their survival and ultimately their reproductive success, which will require balancing their costs against the rewards and hence assessing the net benefits gained. Disentangling the economic aspects of the interaction for each participant has become a major area of study in pollination ecology, and this chapter explicitly considers the costs that may be incurred and that have to be offset against the rewards gathered, as outlined in the last three chapters....

  7. PART III POLLINATION SYNDROMES?
    • Chapter 11 TYPES OF FLOWER VISITORS: SYNDROMES, CONSTANCY, AND EFFECTIVENESS
      (pp. 261-287)

      In the next few chapters, different kinds of flower visitor are reviewed in some depth, using the literature accumulated for over a century documenting their flower visits and floral selection, their color and scent preferences, their food and energy requirements, and aspects of their behavior on flowers. Here, this is all set in context with an explicit introduction to the idea of pollination syndromes, and a review of evidence that syndromes are both real and useful. Without this background, a newcomer to the field might have difficulty understanding or disentangling the arguments. Once the syndromes themselves have been covered, chapter...

    • Chapter 12 GENERALIST FLOWERS AND GENERALIST VISITORS
      (pp. 288-303)

      Many insects that have other core diets (especially entomophagous species, and a range of herbivores) will top up on some floral nectar at times for an easy energy boost, and thus become potential occasional generalist pollinators. However, alongside these there are some rather more regular flower visitors, spending some part of most of their adult lives feeding in flowers, and they can be seen as a generalist flower visitor cohort, constituting a predictable part of the visitor spectrum of some kinds of flowers. These regular visitors include a range of beetles, and some social and solitary wasps, together with a...

    • Chapter 13 POLLINATION BY FLIES
      (pp. 304-321)

      The flies (order Diptera) constitute a very diverse group of insects, all characterized by just one pair of wings, the ancestral rear pair being modified as flightand balance-control organs termed halteres. Hence flies are often very agile fliers, able to take off and land in any direction and often to hover (rare in other insects). Fly mouthparts are essentially suctorial, but can be either piercing and sucking (using either plant or animal fluids) or merely sucking and lapping without the ability to pierce tissues. Many types of fly have the ability to regurgitate saliva onto potential foodstuffs, making the material...

    • Chapter 14 POLLINATION BY BUTTERFLIES AND MOTHS
      (pp. 322-336)

      The order Lepidoptera contains the butterflies and moths and represents around 10%–11% of all described insect species. The types that are relevant here are mostly rather large insects (although there are also many thousands of species of small micromoths), but they are usually not particularly strong fliers, flying effectively only over short ranges. Their larval stages (caterpillars) are herbivorous, feeding on plant leaves or occasionally woody material or flowers; but as adults all are liquid feeders, sucking up fluids using a long, coiled, and elastic proboscis. This unusual tongue can be used to feed on many possible liquids, including...

    • Chapter 15 POLLINATION BY BIRDS
      (pp. 337-355)

      Bird pollination orornithophilyis a widespread phenomenon, underappreciated in early literature as it is absent in Europe; but it is familiar through much of the United States and as far north as Alaska and occurs throughout the tropics, in the eastern Mediterranean and Middle East (although not in the more northern parts of Asia), as well as in most of Australasia and Africa. Flower-visiting birds are also surprisingly widespread taxonomically, the habit being recorded in at least 50 families, although many of these are only occasional visitors and do more damage to flowers than they do good in transferring...

    • Chapter 16 POLLINATION BY BATS
      (pp. 356-369)

      Flowers visited and pollinated by bats constitute the syndrome termed chiropterophily, as bats were traditionally united in the mammalian order Chiroptera although they are now classified as two distinct and separately evolved orders, Megachiroptera and Microchiroptera. Bats are primarily nocturnal, and as flying endothermic mammals have extremely high energy demands (chapter 10). Furthermore, their flower visits often require hovering for short periods (with wing beats of 12–16 per second and involving an upward tilt of the wings to generate lift); this increases their energy demand further, although—somewhat surprisingly—not by an enormous amount (see Winter and van Helversen...

    • Chapter 17 POLLINATION BY NONFLYING VERTEBRATES AND OTHER ODDITIES
      (pp. 370-377)

      Birds and bats are well known as pollinators, and each has merited its own chapter, but there are also some rather infrequent instances of pollination by other vertebrates, lacking any kind of true flight but able to access flowers either by climbing and gliding among trees or by seeking pendant flowers close to the ground. Most are mammals, but we deal first with a few cases of pollination from the lower vertebrates.

      Are the vertebrate ectotherms—fish, amphibians, and reptiles—of any value to flowers as pollinators? Fish are not recorded as flower visitors, for fairly obvious reasons. But they...

    • Chapter 18 POLLINATION BY BEES
      (pp. 378-417)

      Bees are very special as flower visitors, because almost uniquely they use both nectar and pollen as foods and rely totally on them for both adult and larval nutrition. Adults eat nectar and usually some pollen as well; larvae eat large quantities of both pollen and nectar (converted into honey). Thus any one bee is collecting not just for her own needs but for the offspring; her own sons and daughters if she is solitary, as most bees are, or the queen’s offspring in the less common (but often much more noticeable) social species. The sheer number of visits made...

    • Chapter 19 WIND AND WATER: ABIOTIC POLLINATION
      (pp. 418-433)

      Abiotic pollination involves the transmission and capture of pollen through a fluid medium, either air or water, and it occurs in at least 60 angiosperm families. Although it was once thought to be a somewhat random process, it is now clear that abiotic pollination is quite sophisticated, with significant adaptations in both the pollen releasing and pollen capturing processes that improve pollination efficiency (Cox 1991; Ackerman 2000). Phylogenetically controlled analyses show that, contrary to some earlier views, abiotic pollination gives rise to similar levels of species richness to those found in biotically pollinated sister groups, and that flowering periods are...

    • Chapter 20 SYNDROMES AND WEBS: SPECIALISTS AND GENERALISTS
      (pp. 434-480)

      In recent years, many pollination biologists have embarked upon a reassessment of the classical approach to their subject, as established above all by Sprengel, Darwin, Vogel, and van der Pijl. For about 150 years the main emphasis was on showing the adaptive value of floral traits in relation to particular visitors, and then in showing how neatly plants can control these visitors to achieve cross-pollination. In turn this led to the establishment of particular relationships as pollination syndromes set out in chapter 11 and pursued in detail through chapters 12–19, where major groups of flower visitors were associated with...

  8. PART IV FLORAL ECOLOGY
    • Chapter 21 THE TIMING AND PATTERNING OF FLOWERING
      (pp. 483-502)

      Plants should flower in ways that maximize their own reproductive success. The “flowering pattern” is a composite of the timing and frequency of individual flowers opening, and also of flower longevity. These phenological factors vary between species but also within a species (and often between sexes for dioecious species). They may additionally be affected by abiotic phenomena, as well as by conflicting selection from pollinators, herbivores, and seed dispersers. Phenology can also in its turn affect pollinator attraction and, by altering pollinator behavior, can change pollinator efficiency. Flowering phenology can influence the plant’s manipulation of its visitors in ways that...

    • Chapter 22 LIVING WITH OTHER FLOWERS: COMPETITION AND POLLINATION ECOLOGY
      (pp. 503-523)

      Plants rarely occur in isolation, but grow and flower as part of a community of mixed species; and they are rarely visited by just one kind of animal, but receive visits from several potential pollinator types, some of which will be shared with other plants. Thus plantpollinator interactions have a strong community component, and both plants and animals are subject to potential competitive interactions. This was recognized very early on in pollination biology (e.g., Robertson 1895; and see review by Mitchell et al. 2009). However, many early studies largely side-stepped the issue, merely looking at a single plant and its...

    • Chapter 23 CHEATING BY FLOWERS: CHEATING THE VISITORS AND CHEATING OTHER FLOWERS
      (pp. 524-541)

      Since pollination is not an altruistic exercise, and there is a conflict of needs, both plants and pollinators are liable to cheat to their own benefit, and deception is very common in pollination biology (reviewed by Wiens 1978; Little 1983; Dafni 1984; Renner 2006). For a plant, this essentially means getting pollinated and hence fertilized without giving up any reward or resources. This can commonly be achieved by resembling a rewarding species, so attracting scouting animals by deceit, or less commonly by mimicry of objects other than flowers to which pollinators might be attracted for reproductive purposes. For a visiting...

    • Chapter 24 FLOWER VISITORS AS CHEATS AND THE PLANTSʹ RESPONSES
      (pp. 542-553)

      In the last chapter we saw many examples of plants cheating in the plant-pollinator interaction. However, the reverse can also be true—it should at least sometimes pay visitors to gather food from a flower yet resist being manipulated into carrying pollen around, by avoiding the anthers or indeed by eating all the pollen before they move on. This chapter examines some of the kinds of cheating shown by flower visitors and considers what plants can do to avoid the costs of being cheated.

      Many visitors to a flower are classed as illegitimate, meaning that they interact with the flower...

    • Chapter 25 THE INTERACTIONS OF POLLINATION AND HERBIVORY
      (pp. 554-564)

      Herbivores in the broadest sense include not just folivores whose diet is green leaves, but also browsers on twigs and bark, seed predators, underground root feeders, florivores, and even nectar robbers. Herbivory is not just due to animals, though: the effects of fungal spores are often very evident on flowers and flowering patterns, and other decomposers that gain entry through any damage to the plant’s protective surfaces can also have a massive effect on overall plant growth and hence on resources allocated to flowering. Pollinators and herbivores therefore rarely operate completely independently, and although in the past there was a...

    • Chapter 26 POLLINATION USING FLORIVORES: FROM BROOD SITE MUTUALISM TO ACTIVE POLLINATION
      (pp. 565-574)

      In chapter 23 various one-sidedbrood site mimicrieswere described where the plant benefits from cheating its visitor, whose progeny usually die because their mother has been deceived into laying on a floral tissue that was mimicking the normal egg-laying site. This chapter deals instead withbrood site mutualisms, where there may be no mimicry involved and where the pollinators also benefit: their eggs hatch and the progeny survive by feeding on plant tissues, so they are sometimes termednursery pollinators. Here pollination success affects not only plant fitness but also pollinator fitness, and the balance between costs and benefits...

    • Chapter 27 POLLINATION IN DIFFERENT HABITATS
      (pp. 575-604)

      Thus far pollination has been dealt with in a collective sense, but it will have been apparent that examples from different habitats have often given rather different impressions of the complexity and level of specialization involved. This chapter therefore dissects the issues that are to the fore in current debates in different kinds of ecosystems and habitats, in search of some messages on community structures and how they affect plant-pollinator interactions.

      Deserts occur in many low-latitude areas just to the north and south of the equator, between 15⁰ and 40⁰ latitude (fig. 27.1). Most are both hot and dry by...

    • Chapter 28 THE POLLINATION OF CROPS
      (pp. 605-619)

      The importance of bee pollination to crops has been well known for at least two millennia, and several ancient civilizations cultivated honeybees or stingless bees in wooden or pottery hives. Likewise, humans have attempted to improve crop productivity for millennia, first by selecting the plants with the more desirable traits but latterly using plant breeding and hybridization techniques, whether at the whole-plant level or more directly at the genetic level. Today there is a critically important applied aspect to pollination ecology, and much room for improvement in our knowledge of what makes a good pollinator for different kinds of crops,...

    • Chapter 29 THE GLOBAL POLLINATION CRISIS
      (pp. 620-638)

      For nearly three decades now there have been well-substantiated reports of declines in pollinators worldwide, and the problems were explicitly recognized in the UN Sao Paulo declaration (1998–99), so that pollination disruption is at last being emphasized as a major issue (Kearns et al. 1998). The International Pollinator Initiative (IPI) was set up in 2000 to coordinate worldwide activities. However, the direct evidence for ecosystem-level effects has been slow to appear (Cane and Tepedino 2001; Kevan and Phillips 2001), with uncertainty still over the extent of pollen limitation (Ashman et al. 2004; see chapter 3, sectionPollen Limitation) or...

  9. APPENDIX
    (pp. 639-642)
  10. GLOSSARY
    (pp. 643-662)
  11. REFERENCES
    (pp. 663-750)
  12. SUBJECT INDEX
    (pp. 751-767)
  13. INDEX OF ANIMAL GENERA
    (pp. 768-770)
  14. INDEX OF PLANT GENERA
    (pp. 771-778)