Ecological Genetics

Ecological Genetics

David J. Merrell
Copyright Date: 1981
Edition: NED - New edition
Pages: 512
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  • Book Info
    Ecological Genetics
    Book Description:

    Ecological Genetics was first published in 1981. Population genetics and population ecology originally developed independently, but are now merging into a discipline known as ecological genetics. Thus far, the union has been an uneasy one, and this book is an effort to further the union. The ecological geneticist is an experimental naturalist, concerned not just with the distribution and abundance of populations but with their genetic compositions as well. The methodology involves field and laboratory research and permits study of the ways that natural populations adapt to their physical and biological environments. In essence, ecological genetics is the study of evolution in progress. This approach can be applied to a variety of biological problems of both theoretical and practical interest, ranging from the origin of species to the origin of pesticide resistance. With this perspective, David J. Merrell discusses the population dynamics and the mechanism of evolution and speciation which includes mutation, selection, migration, and genetic drift. This book will be useful for advanced undergraduate and graduate level courses in the biological sciences, especially for those dealing with population biology or evolution.

    eISBN: 978-0-8166-5520-5
    Subjects: Health Sciences

Table of Contents

  1. Front Matter
    (pp. i-iv)
  2. Preface
    (pp. v-vi)
  3. Acknowledgments
    (pp. vii-viii)
  4. Table of Contents
    (pp. ix-2)
  5. CHAPTER 1 The Nature of Ecological Genetics
    (pp. 3-12)

    Ecological genetics represents a union between population genetics and population ecology, combining certain aspects of each discipline, but also differing in certain respects from both. Even though both population ecology and population genetics are concerned with populations, the two fields developed independently until quite recently. Population genetic theory, developed initially by R. A. Fisher, J. B. S. Haldane, and S. Wright, is based on the principles of heredity established by Mendel, Morgan, and their successors. Population ecology developed in the absence of a comparable set of general ecological principles. The union of population genetics and population ecology has been an...

  6. CHAPTER 2 Adaptation
    (pp. 13-28)

    With the approach of winter in the northern United States, some species migrate south. The nighthawks, chimney swifts, and swallows start their migrations in late August and are followed by other species in September and October, with some of the hawks and eagles and waterfowl not leaving until November when the lakes begin to freeze. Other species, especially small mammals, go into hibernation, a period of dormancy that lasts through the winter. The snowshoe hare remains active, but the prospect of a northern winter turns his coat white from its drab summer brown. Although they do not breed in winter,...

  7. CHAPTER 3 Biological Variation
    (pp. 29-56)

    If someone were to ask you about variation in wild populations of gray squirrels, or robins, or cottontail rabbits, you would probably respond that, to you, one squirrel, robin, or rabbit looks pretty much like another. Superficially, this appears to be true, for marked individual variation seems to be rare in wild populations. However, in humans we can readily recognize individual differences between people. Closer observation of wild populations of other species would undoubtedly enable us to begin to recognize individual differences even though it is true that natural populations of species are usually quite uniform phenotypically. It is probably...

  8. CHAPTER 4 Mutation
    (pp. 57-71)

    The modern concept of evolution stems from several sources. Mendel’s discovery of the particulate nature of inheritance (1866) formed the basis for the Castle-Hardy-Weinberg equilibrium (Castle, 1903; Hardy, 1908; Weinberg, 1908). Darwin, in hisOriginof Species (1859), developed the theory of natural selection as the mechanism for adaptation. In 1901 de Vries postulated that mutations also played a role in the evolutionary process. These separate strands were woven into a single pattern by the work of R. A. Fisher (1930) inThe Genetical Theory of Natural Selection,Sewall Wright (1931) in “Evolution in Mendelian Populations,” and J. B. S....

  9. CHAPTER 5 Natural Selection
    (pp. 72-116)

    The concept of natural selection won wide acceptance following the publication of Darwin’sOrigin of Speciesin 1859. Darwinian natural selection was based on several observations and the logical conclusions to be drawn from them. First, Darwin observed that the reproductive potential of any species was far greater than needed to replace the parents in the previous generation. The reproductive capacity is geometric or logarithmic. Even for elephants, which he assumed to produce, between the ages of 30 and 90, only six progeny, he estimated that one pair would have 19 million living descendants after just 750 years. Second, despite...

  10. CHAPTER 6 Balanced Polymorphism
    (pp. 117-133)

    In the literal sense, polymorphic means having many forms. Thus, not all polymorphisms in natural populations are necessarily genetic. In species with several generations per year, the different environmental conditions at different seasons may cause individuals with different phenotypes to develop, even though their genotypes are essentially the same. Furthermore, individuals developing at the same time, but under different environmental regimes, may have different phenotypes. In some species juvenile and adult forms (bird plummage, for example) may be quite distinct and therefore polymorphic. These developmental and environmental polymorphisms may lead to some confusion in the study of natural populations because...

  11. CHAPTER 7 Polymorphism and Population Dynamics
    (pp. 134-177)

    Before continuing the discussion of polymorphism, we must first consider the factors influencing the numbers of individuals in a given species. To deal with this, some definitions are required. One word widely used and often undefined ispopulation.For the purposes of this discussion, apopulationis a group of organisms of the same species occupying a particular space at a particular time. Some of the attributes of a population are derived from the nature of its individual members. Other attributes are unique to the group as a whole and are not characteristics of individuals. Some characteristics of populations are...

  12. CHAPTER 8 Genetic Loads
    (pp. 178-193)

    Chetverikov (1926) was the first to report that many “normal” individuals in wild populations carried recessive mutant genes in the heterozygous condition, a finding subsequently confirmed repeatedly. Most of these recessives were found to be detrimental to some degree when homozygous. Therefore, these homozygotes represent a reproductive waste and reduce the overall fitness of the population, and thus constitute agenetic loadthe population has to bear. If the mutants are not completely recessive but have adverse effects in the heterozygotes, the load includes the heterozygotes as well. The concept was first dealt with by Haldane (1937) and the expression...

  13. CHAPTER 9 Chromosomal Polymorphism
    (pp. 194-225)

    Thus far, we have dealt primarily with diploid, sexually reproducing species in which the chromosome complement has been assumed to be constant among individuals and the variation confined to allelic variation at many different loci within the fixed framework provided by the chromosomes. However, the broad definition of mutation in Chapter 4 included chromosomal changes as well as gene mutations as a possible source of variation in natural populations. The fact is that chromosomal changes are found in natural populations, both within a given species and between closely related species. Thus, chromosomal variation appears to play a significant role in...

  14. CHAPTER 10 Random Genetic Drift
    (pp. 226-244)

    Natural selection, mutation, and migration or gene flow can be thought of as directional evolutionary forces, producing predictable changes in gene frequency if the mutation rates, the selection coefficients, and the migration coefficients are known. For this reason they are also sometimes known as evolutionary pressures. Although mutation is treated as a directional force, it also has its random aspects. For example, even though mutation rates can be estimated, it is not possible to predict which particular gene will mutate at a given time. Moreover, even though mutagenic environmental agents such as radiation and chemicals are known to increase mutation...

  15. CHAPTER 11 Migration and Gene Flow
    (pp. 245-277)

    Even if agreement were possible on just what constitutes a species, it would not be possible to say how many living species there are. New species are being described all the time, but there is no way of knowing how many more unknown species remain to be identified and described. Even the number of known species is uncertain, but the estimates seem to be of the order of a million or more, and the speculations about the total number of living species range from about two to four million. It is even more hazardous to try to guess the total...

  16. CHAPTER 12 The Origin of Races
    (pp. 278-316)

    We have discussed variation in natural populations, primarily in terms of polymorphic variation within a single breeding population or deme. In the previous chapter, we dealt with population structure and gene flow between populations, but our primary concern was still the effect of subdivision and gene flow on gene frequencies within a single deme. Now we shall consider geographical or polytypic variation in an effort to understand the nature and origin of the genetic differences between different populations of the same species.

    When two populations of the same species are compared, the observed differences may be due to genetic differences,...

  17. CHAPTER 13 Neutralist vs. Selectionist
    (pp. 317-357)

    The first analyses of electrophoretic variation in enzymes and soluble proteins in natural populations were conducted by Harris (1966) in humans, by Hubby and Lewontin (Hubby and Lewontin, 1966; Lewontin and Hubby, 1966) inD.pseudoobscura,and by Johnson et al. (1966) inD.ananassae.As pointed out in Chapter 3, they reported what was at that time considered to be a remarkably high level of genetic variation in natural populations. The studies in humans and inDrosophilaagreed in the finding that, on the average, about a third of all loci studied were polymorphic and that the average proportion of heterozygous...

  18. CHAPTER 14 The Species Concept
    (pp. 358-399)

    The full title of Darwin’s major work wasThe Origin of Species by Means of Natural Selection or The Preservation of Favoured Races in the Struggle for Life. In the second chapter, “Variation under nature,” he discussed the problems involved in distinguishing between individual differences and varieties, between varieties and subspecies, and between subspecies and species, and then pointed out that no clear lines of demarcation had as yet been drawn among these different forms. He used this as an argument favoring the o o idea that species are not immutable creations, that these different forms are different stages in...

  19. CHAPTER 15 The Origin of Species
    (pp. 400-421)

    The origin of species is a complex process. For the most part, thus far we have adhered to the conventional concept of the origin of species, that of geographic or allopatric speciation, whose most vigorous advocate has been Mayr (1963, 1970). The following statement (Mayr, 1970) reflects a widespread attitude about the origin of species.

    That geographic speciation is the almost exclusive mode of speciation among animals, and most likely the prevailing mode even in plants, is now quite generally accepted. [Further on he wrote] The theory of geographic speciation . . . states that in sexually reproducing animals a...

  20. CHAPTER 16 Competition
    (pp. 422-450)

    Thus far, we have considered only the population dynamics of a single species. However, now we shall consider the nature of interactions between two different species.

    The population size of a species is affected by its own innate characteristics, its γ value, for example, and by the carrying capacity of the environment— that is, by the environmental conditions that determine K. In addition, the size of a population may be influenced in positive or negative ways by the presence of another species, the possibilities of which are outlined in Table 16-1. Interactions 7 through 9 are positive. Interactions 5 and...

  21. References
    (pp. 453-492)
  22. Index
    (pp. 495-500)