Summary: Wittkopp et al. (2009)

Intra- and interspecific phenotypic variation may be influenced by genetic mechanisms, but the allelic relationship underlying intraspecific polymorphism and interspecific divergence is unknown. Wittkopp et al. (2009) examined the genetic basis of variation in pigmentation within and between two closely related Drosophila species (D. americana and D. novamexicana) to investigate the relationship between intraspecific polymorphism and interspecific divergence. They found that changes linked to both the tan and ebony genes in closely related Drosophila species contributes to divergence in pigmentation. Furthermore, they found that the alleles linked to these two genes in one species contributed to the variation in the other species, suggesting the similar phenotypes in a population may have different underlying genotypes. The genetic variation present in the common ancestor of these two species likely gave rise to both intraspecific polymorphism and interspecific divergence, as the alleles appear to predate speciation.