GENETIC AND PHENOTYPIC DIFFERENTIATION AND GEOGRAPHIC DISTANCE IN FOUR SPECIES OF LEPIDOPTERA.

Abstract

Genetic differentiation between geographic populations is the result of local adaptation. Since any local population is most likely to differentiate from the least isolated neighboring population rather than from one that is more closely adapted to parallel environmental conditions but is more isolated, the amount of genetic differentiation that occurs across a species' range depends on and should be proportional to the absolute amount of environmental change that has occurred over this distance rather than on the corresponding net amount of change. The result may be the accumulation of considerable genetic differentiation over a geographic distance even though the net amount of environmental change has been little or nothing. Genetic differentiation between populations involves the accumulation of differences in single genes and other functional units (such as inversions), affecting a large number of polygenic systems. Genetic differentiation should cause many phenotypic changes of varying degrees of apparentness, and some idea of relative degree of differentiation should be arrived at by totalling up all of the perceptible phenotypic differences between populations. When polygenic systems differing in a substantial number of genetic units are combined in a single zygote, there should be a breakdown in the integration of the genotype that is produced. Thus, the relative differentiation of populations should also be evidenced by