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

Statistical method for testing the neutral mutation hypothesis by DNA polymorphism.

▪ Abstract Changes in ploidy occurred early in the diversification of some animal and plant lineages and represent an ongoing phenomenon in others. While the prevalence of polyploid lineages indicates that this phenomenon is a common and successful evolutionary transition, whether polyploidization itself has a significant effect on patterns and rates of diversification remains an open question. Here we review evidence for the creative role of polyploidy in evolution. We present new estimates for the incidence of polyploidy in ferns and flowering plants based on a simple model describing transitions between odd and even base chromosome numbers. These new estimates indicate that ploidy changes may represent from 2 to 4% of speciation events in flowering plants and 7% in ferns. Speciation via polyploidy is likely to be one of the more predominant modes of sympatric speciation in plants, owing to its potentially broad-scale effects on gene regulation and developmental processes, effects that can produce immed...

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Polyploid Incidence and Evolution

Many species are experiencing sustained environmental change mainly due to human activities. The unusual rate and extent of anthropogenic alterations of the environment may exceed the capacity of developmental, genetic, and demographic mechanisms that populations have evolved to deal with environmental change. To begin to understand the limits to population persistence, we present a simple evolutionary model for the critical rate of environmental change beyond which a population must decline and go extinct. We use this model to highlight the major determinants of extinction risk in a changing environment, and identify research needs for improved predictions based on projected changes in environmental variables. Two key parameters relating the environment to population biology have not yet received sufficient attention. Phenotypic plasticity, the direct influence of environment on the development of individual phenotypes, is increasingly considered an important component of phenotypic change in the wild and should be incorporated in models of population persistence. Environmental sensitivity of selection, the change in the optimum phenotype with the environment, still crucially needs empirical assessment. We use environmental tolerance curves and other examples of ecological and evolutionary responses to climate change to illustrate how these mechanistic approaches can be developed for predictive purposes.

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Adaptation, plasticity, and extinction in a changing environment: towards a predictive theory.

Theoretical studies of life history evolution almost unanimously incorporate some form of tradeoff between life history variables, such as reduced parental survival due to increased reproductive effort. These tradeoffs, or costs of reproduction, are fundamental in predicting the optimal life history in any given environment. The importance of such costs in theoretical models has motivated researchers to check that they exist by seeking an association between some component of reproductive effort, such as fecundity, and some form of cost, such as parental survival. Four methods have been used for making these evaluations: 1) Phenotypic correlations, where some index of reproductive effort is correlated with a potential cost, 2) Experimental manipulations, where reproduction is directly manipulated and a cost-related response is measured, 3) Genetic correlations, where formal quantitative genetic designs are used to estimate the genetic correlation between some component of reproductive effort and some component of cost, and 4) Correlated responses to selection, where artificial selection causes correlated changes in reproductive effort and some component of costs. Because the theoretical studies are models of evolution, I argue that a relevant empirical study must deal with genetically based tradeoffs. By this criterion, only the last two methods (which represent a small minority of the reviewed studies) properly address the "costs" dealt with by theoreticians; however, this evaluation is not intended as a litmus test for the merits of a given approach to the problem. I discuss both the important contributions of the first two methods to our understanding of the costs of reproduction and the limitations of the last two methods in assessing "costs".

Costs of reproduction: an evaluation of the empirical evidence

Combined effects of salinity and temperature on survival and reproduction of five species of Artemia

The principles of island biogeographic theory are applied to the species diversity and distribution of various taxa within lakes of central New York state. Greater emphasis is placed on mollusc species, owing to the extensiveness of surveys, but data for zooplankton and fish species are also presented. Species diversity was found to correlate positively with lake surface area, with best descriptive equations being power curve functions. z-values of 0.23, 0.17 and 0.24 were found respectively for mollusc, zooplankton, and fish species-area equations. Species turnover rates over a half-century interval were calculated to be 0.50%/year for molluscs in a large lake, and 0.28%/year for the zooplankton communities of twelve lakes. Zooplankton turnover rates were negatively correlated with lake surface area and initial species number.

Lakes as Islands: Biogeographic Distribution, Turnover Rates, and Species Composition in the Lakes of Central New York

The genus Artemia Leach 1819 is an exceptionally favorable system for the study of evolutionary processes. With regard to the study of evolutionary genetics, sexual populations may be compared with asexual forms. This chapter aims to anticipate some taxonomic problems with examples of partial barriers to gene flow. It examines the influence of heterozygosity on female reproductive success. The chapter discusses the presence of partial reproductive isolation within the A. franciscana superspecies subsequently under the headings "Ecological Isolation" and "Hybridization". The genus Artemia is a complex of sibling species and superspecies defined by the criterion of reproductive isolation. The chapter reviews the cross-fertility tests which were the basis of the diagnosis of sibling species in Artemia. Among the bisexual populations, the first demonstrations of reproductive isolation were between wild-type Mediterranean saltern shrimps and either "California shrimps" or A. persimilis. In an ideal experimental design, each of the known Artemia populations would be crossed in a matrix.

Taxonomy and population genetics of Artemia

Reproductive and lifespan characteristics were determined for 12 populations of the brine shrimp, Artemia Based upon geographical distribution and reproductive mode these could be separated into three distinct groups: obligate parthenogenetic populations, Old World sexual popu- lations, and New World sexual populations The three groups were found to be distinctly different in regard to reproductive and lifespan characteristics Variance levels were compared between uniparental and biparental populations, allowing estimates to be made of the relative contribution of the genetic and environmental components for 11 life history traits The environmental portion was estimated to be 100% for encystment traits and for the length of the prereproductive period, while the number of offspring produced (both as a lifetime total and a production rate) and the recovery period between broods had genetic components of variance > 50% To test for the interrelatedness of life history traits, a correlation coefficient matrix was constructed In contradiction to most theoretical assumptions, extremely low correlation coefficients were found between the length of the female prereproductive period and the remaining lifespan and reproductive traits However, recovery time between broods showed a significant positive correlation with number of broods produced, total offspring produced, and female lifespan

Partitioning genetic and environmental components of reproduction and lifespan in Artemia.

During the colder climates of the Pleistocene, the ranges of high-elevation species in unglaciated areas may have expanded, leading to increased gene flow among previously isolated populations. The phylogeography of the pygmy salamander, Desmognathus wrighti, an endemic species restricted to the highest mountain peaks of the southern Appalachians, was examined to test the hypothesis that the range of D. wrighti expanded along with other codistributed taxa during the Pleistocene. Analyses of genetic variation at 14 allozymic loci and of the 12S rRNA gene in the mtDNA genome was conducted on individuals sampled from 14 population isolates throughout the range of D. wrighti. In contrast to the genetic patterns of many other high-elevation animals and plants, genetic distances derived from both molecular markers showed significant isolation by distance and genetic structuring of populations, suggesting long-term isolation of populations. Phylogeographical analyses revealed four genetically distinct population clusters that probably remained fragmented during the Pleistocene, although there was also evidence supporting recent gene flow among some population groups. Support for isolation by distance is rare among high-elevation species in unglaciated areas of North and Middle America, although not uncommon among Plethodontid Salamanders, and this pattern suggests that populations of D. wrighti did not expand entirely into suitable habitat during the Pleistocene. We propose that intrinsic barriers to dispersal, such as species interactions with other southern Appalachian plethodontid salamanders, persisted during the Pleistocene to maintain the fragmented distribution of D. wrighti and allow for significant genetic divergence of populations by restricting gene flow.

Robert A. Browne

Papers

Combined effects of salinity and temperature on survival and reproduction of five species of Artemia

Lakes as Islands: Biogeographic Distribution, Turnover Rates, and Species Composition in the Lakes of Central New York

Taxonomy and population genetics of Artemia

Partitioning genetic and environmental components of reproduction and lifespan in Artemia.

Testing Pleistocene refugia theory: phylogeographical analysis of Desmognathus wrighti, a high-elevation salamander in the southern Appalachians.