Evolution in a Variable Environment

Abstract

We develop a general model for the effects of variation in reproductive success on gene-frequency change and phenotypic evolution. Our approach is based on distinguishing among individual, genotypic, and population-level reproductive success and on relating these three levels through correlations. For example, the variance of genotypic reproductive success can be expressed by individual-level variance and by the correlations among individuals. We use these correlations to show the simple relationship among earlier models of selection on the variance of reproductive success, of temporal variation in selection, of spatial variation in selection, and of variation in behavioral traits. Our approach also applies to diploid individuals by regarding diploidy as a way to induce correlations in reproductive success between pairs of alleles. We apply our method to patterns of developmental homeostasis, the evolution of iteroparity, and the effects of variability in resource acquisition under nonlinear gains. Finally, we discuss the uses and limitations of the geometric-mean principle, and we provide a precise description and formal methods of analysis for bet hedging and risk aversion