Population Dynamics in Variable Environments. V. The Genetics of Homeostasis Revisited

Abstract

A one-locus stochastic environment model in which genotypes differ in homeostatic ability is analyzed. Each genotype is assigned a set of Leslie matrices, the vital rates of which vary between environments to differing degrees depending on genotype. In contrast to the classical assumption and the results of previous theoretical analyses, the least variable genotype does not necessarily have a selective advantage. In particular, the relative advantage of homeostasis is dependent on environmental frequencies and, more significantly, on the environmental autocorrelation. For a given set of environments, changing autocorrelation can change the allele which is ultimately fixed, or allow a polymorphism to be maintained. In addition, for given environmental conditions, the direction of evolution can qualitatively change depending on which part of the life history is subject to selection. Covariances between vital rates can enhance or eliminate the advantage of the least variable genotype. Finally, it is shown, in contradiction to the prediction of the theory of "genetic homeostasis," that overdominance for homeostatic ability does not necessarily lead to maintenance of polymorphism within a population.