Does the evolutionary ability of Colias butterflies to mate

Does the evolutionary ability of Colias butterflies to mate successfully depend on heterozygosity?

Solution

Yes. The heterozygous males of Colias butterflies have reproductive advantage over homoygous males. This is because, in Colias butterflies multiallelic polymorphisms of the enzymes are common at the phosphoglucose isomerase (PGI) locus. Due to presence of specific PGI alleles, the heterozygotes are able to fly farther distances under broader range of temperatures and exhibited successful mating rates than homozygotes. Ward Watt, Patrick Carter, and Sally Blower hypothesized the mating success of heterozygotes over homozygotes.

Source:

Watt, W. B., P. A. Carter, and S. M. Blower. 1985. Adaptation at specific loci. IV. Differential mating success among glycolytic allozyme genotypes of Colias butterflies. Genetics 109: 157–175.

http://www.genetics.org/cgi/reprint/109/1/157

To test this hypothesis, wild butterflies iare captured and their genotypes are determined. The females are allowed to lay eggs in captivity, and the genotypes of the offspring are determined. The resultant data was useful to determine the genotype of the fathers and mating success rate was measured . It was reported that in two different species of butterflies, Colias eurytheme and Colias philodice, the heterozygous males represented in flying population were only 46 percent and 54 percent respectively. In contrast, these males were accounted for 72 percent and 80 percent, respectively, of successful matings. Therefore, the data was consistent with the hypothesis that heterozygous males have a mating advantage over homozygous males. This also proves that the evolutionary ability of these Colias butterflies to mate successfully depend on heterozygous advantage.