Genetic variation in heterogeneous environments

Abstract

The genetic respponse of a population to the pattern of the environment can be divided into direct and indirect effects. Direct effects refer to adaptive responses due to selective differences between the genotypes. Indirect effects result from the fact that environmental variation affects the population demography (size, subdivision etc.) and this affects the stochastic processes which shape genetic variation. Although the deterministic models show that environmental heterogeneity can help to maintain genetic polymorphism of specific characters, the parameter space leading to a stable polymorphism is heavily constrained, for example due to stochastic changes. Genotype-specific habitat selection and the reversal of genetic dominance in different environmental patches help maintenance of polymorphism considerably. Theories concerning single characters have been extended to explain the overall gene diversity detected by studies of proteins and DNA. Genetic variation in quantitative characters depends both on the pattern of environmental variation and on the genetic correlation of the character states expressed in different habitats. -from Author