Adaptation at specific loci. IV. Differential mating success among glycolytic allozyme genotypes of Colias butterflies.

Male mating success as a function of genotype is an important fitness component. It can be studied in wild populations, in species for which a given group of progeny has exactly one father, by determining genotypes of wildcaught mothers and of sufficient numbers of their progeny. Here, we study male mating success as a function of allozyme genotype at two glycolytic loci in Colias butterflies, in which sperm precedence is complete, so that the most recent male to mate fathers all of a female's subsequent progeny.--For the phosphoglucose isomerase, PGI, polymorphism, we predict mating advantage and disadvantage of male genotypes based on evaluation of their biochemical functional differences in the context of thermal-physiological-ecological constraints on the insects' flight activity. As predicted, we find major, significant advantage in mating success for kinetically favored genotypes, compared to the genotype distribution of males active with the sampled females in the wild. These effects are repeatable among samples and on different semispecies' genetic backgrounds.--Initial study of the phosphoglucomutase, PGM, polymorphism in the same samples reveals heterozygote advantage in male-mating success, compared to males active with the females sampled. This contrasts with a lack of correspondence between PGI and PGM genotypes in other fitness index or component differences.--Epistatic interactions in mating success between the two loci are absent.--There is no evidence for segregation distortion associated with the alleles of either primary locus studied, nor is there significant assortative mating.--These results extend our understanding of the specific variation studied and suggest that even loci closely related in function may have distinctive experience of evolutionary forces. Implications of the specificity of the effects seen are briefly discussed.