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Sex Allocation

Sex Allocation

Copyright Date: 2009
Pages: 482
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  • Book Info
    Sex Allocation
    Book Description:

    Recent decades have witnessed an explosion of theoretical and empirical studies of sex allocation, transforming how we understand the allocation of resources to male and female reproduction in vertebrates, invertebrates, protozoa, and plants. In this landmark book, Stuart West synthesizes the vast literature on sex allocation, providing the conceptual framework the field has been lacking and demonstrating how sex-allocation studies can shed light on broader questions in evolutionary and behavioral biology.

    West clarifies fundamental misconceptions in the application of theory to empirical data. He examines the field's successes and failures, and describes the research areas where much important work is yet to be done. West reveals how a shared underlying theoretical framework unites findings of sex-ratio variation across a huge range of life forms, from malarial parasites and hermaphroditic worms to sex-changing fish and mammals. He shows how research on sex allocation has been central to many critical questions and controversies in evolutionary and behavioral biology, and he argues that sex-allocation research serves as a key testing ground for different theoretical approaches and can help resolve debates about social evolution, parent-offspring conflict, genomic conflict, and levels of selection.

    Certain to become the defining book on the subject for the next generation of researchers,Sex Allocationexplains why the study of sex allocation provides an ideal model system for advancing our understanding of the constraints on adaptation among all living things in the natural world.

    eISBN: 978-1-4008-3201-9
    Subjects: Developmental & Cell Biology, Ecology & Evolutionary Biology

Table of Contents

  1. Front Matter
    (pp. i-vi)
  2. Table of Contents
    (pp. vii-x)
  3. Acknowledgments
    (pp. xi-xii)
  4. CHAPTER 1 Sex Allocation
    (pp. 1-13)

    In this chapter, I describe my reasons for writing this book. In order to provide some context, I start by presenting the problems of sex allocation and a short, potted history of the field. I then provide a discussion of why I hope this book will prove useful, a description of the book contents, and tips on how to read it.

    Sex allocation is the allocation of resources to male versus female reproduction in sexual species (Charnov 1979c, 1982). Sex allocation depends on the breeding system of a species, as well as on how reproduction is carried out within each...

  5. CHAPTER 2 The Düsing-Fisher Theory of Equal Investment
    (pp. 14-32)

    Fisher’s theory of equal investment provides the basic null model for sex allocation theory, but it is also the foundation for all subsequent theoretical developments. This theory has firm theoretical foundations, established both before and after Fisher’s influential work. However, attempts to test Fisher’s prediction of equal investment in the sexes will usually be in vain, because the conditions required for this are likely to be extremely rare. Instead, it is more productive to test the frequency-dependent nature of Fisher’s theory by perturbing the population sex ratio and then examining whether it evolves back toward equal investment. Some species with...

  6. CHAPTER 3 Interactions between Relatives I: Cooperation and Competition
    (pp. 33-72)

    Biased sex allocation can be favored when relatives compete or cooperate over a very wide range of biological circumstances. Cooperation or competition between relatives has been suggested as an explanation for biased sex allocation in a variety of organisms, including birds, mammals, reptiles, insects, mealy-bugs, and plants. In some cases, there is strong empirical support for the predictions of theory. However, much of the work in this area is still at the suggestive phase. Previous empirical research has frequently (1) focused on overall population sex ratios, where unambiguous predictions can rarely be made, and (2) described biases in sex allocation,...

  7. CHAPTER 4 Interactions between Relatives II: Local Mate Competition
    (pp. 73-108)

    When populations are structured such that mating takes place locally and related males compete for mates, a female biased sex ratio is favored by a process that has been termedlocal mate competition(LMC). Work on this topic has provided some of the clearest support for the theory of sex allocation. Specifically, LMC theory (1) is able to explain female biased sex allocation in a wide variety of organisms, including insects, mites, spiders, protozoan parasites, nematodes, snakes, fish, and flowering plants; (2) is able to explain variation between species/populations, as well as cases in which individuals adjust their sex allocation...

  8. CHAPTER 5 Interactions between Relatives III: Extended Local Mate Competition Theory
    (pp. 109-161)

    In the previous chapter, I reviewed Hamilton’s (1967) classic model of local mate competition (LMC) and empirical tests of this model. Here, I describe how LMC theory has been expanded in numerous directions to fit more closely the biology of particular organisms. This work has provided some striking support for sex allocation theory. In addition, bringing this body of work together suggests two recurring themes: (1) predictions for the overall patch sex ratio are relatively unaffected when different individuals on the same patch are selected to produce different sex ratios, and (2) the most common explanations for when empirical data...

  9. CHAPTER 6 Conditional Sex Allocation I: Basic Scenarios
    (pp. 162-209)

    If environmental conditions differentially influence the fitness of males and females, then selection favors conditional sex allocation. This idea, often termed theTrivers and Willard hypothesis, has been applied to explain sex ratio adjustment, environmental sex determination, and sex change. In many cases, this research has been very succesful, explaining empirical patterns and providing qualitive and in some cases even quantitative support for the predictions of theory. However, this is also one of the most misunderstood areas of sex allocation, with it frequently not appreciated that multiple selective factors can be operating, making it very hard to make clear predictions...

  10. CHAPTER 7 Conditional Sex Allocation II: Population Consequences and Further Complications
    (pp. 210-256)

    In the previous chapter, I discussed situations when individuals are selected to adjust their sex allocation in response to environmental conditions. I focused on relatively basic scenarios of what is often termed the Trivers and Willard hypothesis and how it could be applied to situations involving sex ratio adjustment, sex change, and environmental sex determination (ESD). In this chapter, I will discuss the population-level consequences of this conditional sex allocation and a number of more complicated scenarios that can occur. While some of these provide amazing support for sex allocation theory, such as the relative frequency of early maturers in...

  11. CHAPTER 8 Sex Allocation When Generations Overlap
    (pp. 257-275)

    If generations overlap, then perturbations of the stable age distribution can select for facultative adjustment of sex allocation. Such perturbations can occur unpredictably, due to periods of exceptional mortality or recruitment, or predictably, due to cyclical (seasonal) variation in the amount of overlap between generations. This area has received comparatively little theoretical and empirical attention. To date, (1) there is some, but mixed, experimental and observational support for the prediction that individuals adjust their offspring sex ratio in response to adult sex ratios, producing an excess of the rare sex; (2) there are no empirical tests for the predicted influence...

  12. CHAPTER 9 Conflict I: Between Individuals
    (pp. 276-315)

    The evolutionary stable strategy (ESS) sex allocation may differ between the points of view of different individuals, such as parents and their offspring, or between the sexes. The most studied area of sex allocation conflict between individuals is the parent–offspring conflict that occurs in the eusocial hymenoptera—the ants, bees, and wasps. The haplodiploid genetics of these species means that asymmetrical patterns of relatedness occur between individuals, which leads to predictions for how sex allocation should vary across and within populations, depending on whether the workers or the queens are in control. This has allowed some extremely elegant tests...

  13. CHAPTER 10 Conflict II: Sex Allocation Distorters
    (pp. 316-352)

    Evolutionary stable strategy (ESS) sex allocation may differ between the point of view of different genes within an individual. Consistent with this, a diverse range of sex allocation distorting elements have been found that distort the sex allocation toward their selfish interests. These include nuclear genes and cytoplasmic elements, including a number of endosymbionts, such as the much lovedWolbachiaandCardinium(the newWolbachia). Early work in this area focused on showing that sex allocation distorters existed and elucidating the causative agents. More recently, there has been a growing interest in trying to explain the prevalence and diversity of...

  14. CHAPTER 11 General Issues
    (pp. 353-378)

    Sex allocation theory provides an extremely useful tool for addressing very general issues about natural selection. In this chapter, I consider how sex allocation can be exploited for such general purposes, such as furthering our understanding of inclusive fitness and the levels of selection debate, providing some of the clearest examples of the constraints on adaptation, and supplying a case study of how to develop and test evolutionary theory. From an applied perspective, sex allocation theory can inform conservation programs of endangered species, reduce by up to 50% the cost of biocontrol programs, and provide a useful technique for measuring...

  15. References
    (pp. 379-462)
  16. Index
    (pp. 463-466)
  17. Back Matter
    (pp. 467-468)