Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

The Theory of Island Biogeography

A DNA test to sex most birds.

Conditions experienced during early development affect survival and reproductive performance in many bird and mammal species. Factors affecting early development can therefore have an important influence both on the optimization of life histories and on population dynamics. The understanding of these evolutionary and dynamic consequences is just starting to emerge.

Early development and fitness in birds and mammals

The past two decades have seen extensive growth of sexual selection research. Theoretical and empirical work has clarified many components of pre- and postcopulatory sexual selection, such as aggressive competition, mate choice, sperm utilization and sexual conflict. Genetic mechanisms of mate choice evolution have been less amenable to empirical testing, but molecular genetic analyses can now be used for incisive experimentation. Here, we highlight some of the currently debated areas in pre- and postcopulatory sexual selection. We identify where new techniques can help estimate the relative roles of the various selection mechanisms that might work together in the evolution of mating preferences and attractive traits, and in sperm‐egg interactions.

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Sexual selection and mate choice.

Sperm are produced in astronomical numbers compared with eggs, and there is good evidence that sperm competition is the force behind the evolution of many tiny sperm. However, sperm production inevitably has costs. Recent research shows that male ejaculate expenditure is dynamic in both time and space, and that males are sensitive to risks of sperm competition and can vary ejaculate size accordingly. We focus on studies showing that males assess mating status and relative fecundity of females, and reveal that modulation of ejaculate investment by males can sometimes result in sperm limitation for females.

Sperm competition, male prudence and sperm-limited females

A waning success in siring counters a ram's high score in competition for ewes.

/pdf/dominant-rams-lose-out-by-sperm-depletion-3n4vx7oa3p.pdf

Dominant rams lose out by sperm depletion

Most animal species are infected with multiple parasite species; however, the role of interspecific parasite interactions in influencing parasite dynamics and shaping parasite communities has been unclear. Although laboratory studies have found evidence of cross-immunity, immunosuppression and competition, analyses of hosts in the field have generally concluded that parasite communities are little more than random assemblages. Here we present evidence of consistent interspecific interactions in a natural mammalian system, revealed through the analysis of parasite intensity data collected from a free-ranging rabbit (Oryctolagus cuniculus) population, sampled monthly for a period of 23 yr. The wild rabbit plays host to a diverse gut helminth community that reflects the communities seen in other economically important domestic herbivores. These findings suggest that parasite interactions could have profound implications for the dynamics of parasite communities. The efficacy of parasite control programmes could be jeopardized if such interactions are not taken into account. In contrast, a clear understanding of such interactions may provide the basis for the development of more environmentally acceptable methods of parasite control.

/pdf/competition-and-mutualism-among-the-gut-helminths-of-a-3eslc37dfx.pdf

Competition and mutualism among the gut helminths of a mammalian host

Male contests for access to receptive females are thought to have selected for the larger male body size and conspicuous weaponry frequently observed in mammalian species. However, when females copulate with multiple males within an oestrus, male reproductive success is a function of both pre- and postcopulatory strategies. The relative importance of these overt and covert forms of sexual competition has rarely been assessed in wild populations. The Soay sheep mating system is characterized by male contests for mating opportunities and high female promiscuity. We find that greater horn length, body size and good condition each independently influence a male's ability to monopolize receptive females. For males with large horns at least, this behavioural success translates into greater siring success. Consistent with sperm-competition theory, we also find that larger testes are independently associated with both higher copulation rates and increased siring success. This advantage of larger testes emerges, and strengthens, as the number of oestrous females increases, as dominant males can no longer control access to them all. Our results thus provide direct quantitative evidence that male reproductive success in wild populations of mammals is dependent upon the relative magnitude of both overt contest competition and covert sperm competition.

/pdf/overt-and-covert-competition-in-a-promiscuous-mammal-the-1tajm3lyzy.pdf

Overt and covert competition in a promiscuous mammal: the importance of weaponry and testes size to male reproductive success.

Although climate change apparently affects the breeding patterns of many animals1,2,3, the wider implications for breeding success are unclear. Here we describe an energy trade-off between reproduction and maintenance that occurs during cold weather in great tits (Parus major L.), pointing to a thermal constraint on the timing of egg laying. Our observations indicate that the fine-scale pattern of climate change could be critical to the reproduction of some species and underlies previously unexplained variation in the breeding success of other temperate birds.

Climate change and constraints on breeding

1. Though models of life-history decisions are traditionally based on age-related changes in the costs and benefits of reproduction, in nature both costs and benefits vary with individual differences in phenotype as well as with environmental changes. 2. Using long-term records of individual reproduction and survival in the Soay sheep of St Kilda, we show that the costs and benefits of breeding to animals of different weight categories vary with population density. 3. Subsequently, we use stochastic dynamic programming to predict the optimal fecundity of animals belonging to each category at high and low population density. Optimal strategies of fecundity vary with population density as well as between different weight categories of sheep. However, there is no evidence that the sheep track density-related changes in optimal fecundity. Instead, their behaviour approximates to an average, weight-related optimum that is well adapted to the range of conditions that they encounter.

https://www.jstor.org/stable/pdfplus/5667.pdf

Ian R. Stevenson

Papers

Dominant rams lose out by sperm depletion

Competition and mutualism among the gut helminths of a mammalian host

Overt and covert competition in a promiscuous mammal: the importance of weaponry and testes size to male reproductive success.

Climate change and constraints on breeding

Population fluctuations, reproductive costs and life-history tactics in female soay sheep