Ecological population genetics: the interface between genes and the environment.

We review recent studies in ecological genetics considering the way genes interact with the environment. Studies on morphological and allozyme polymorphisms continue to highlight problems in identifying selective factors. Selection on allozymes as well as quantitative traits may only occur under specific conditions. Responses to toxins illustrate how adaptive changes can be based on major genes with polygenic modifiers. Analyses of continuous variation in ecologically relevant traits suggest low levels of heritable variation in some natural situations and emphasize the importance of genetic interactions. It is still not clear if adaptive responses in quantitative traits tend to involve major or minor genes. There is some evidence for genetic tradeoffs among environments and life history traits. Low levels of genetic variation, tradeoffs, and gene flow may restrict distributions and habitats occupied by species, but their relative importance remains unclear.