Polymorphism and predictability at the ?-glycerophosphate dehydrogenase locus in Colias butterflies: Gradients in allele frequency within single populations

Abstract

Heterozygosity at the α-glycerophosphate dehydrogenase locus of five species of Colias butterflies is widespread in montane populations; alpine and lowland populations are not heterozygous. Within a single demographically characterized population of C. meadii where the population extends from alpine down into montane habitats, a marked cline in allele frequency is seen. Such within-population clines suggest the involvement of strong selection across the marked ecological interface. Thermal factors are the most likely causative agents, but associative overdominance is not excluded.