Genetic hitchhiking associated with life history divergence and colonization of North America in the European corn borer moth.

A primary goal for evolutionary biology is to reveal the genetic basis for adaptive evolution and reproductive isolation. Using Z and E pheromone strains the European corn borer (ECB) moth, I address this problem through multilocus analyses of DNA polymorphism. I find that the locus Triose phosphate isomerase (Tpi) is a statistically significant outlier in coalescent simulations of demographic histories of population divergence, including strict allopatric isolation, restricted migration, secondary contact, and population growth or decline. This result corroborates a previous QTL study that identified the Tpi chromosomal region as a repository for gene(s) contributing to divergence in life history. Patterns of nucleotide polymorphism at Tpi suggest a recent selective sweep and genetic hitchhiking associated with colonization of North America from Europe ~200 generations ago. These results indicate that gene genealogies initially diverge during speciation because of selective sweeps, but differential introgression may play a role in the maintenance of differentiation for sympatric populations.