Genetics of sexual isolation in females of theDrosophila simulansspecies complex

Abstract

Summary: Genetic analysis of hybrids betweenDrosophila simulansandD. sechelliashows that sexual isolation in females is caused by at least two genes, one on each major autosome, while the X chromosome has no effect. These results are similar to those of a previous study of hybrids betweenD. simulansand another sibling species,D. mauritiana. In this latter hybridization, each arm of the second chromosome carries genes causing sexual isolation in females, implying a total divergence of at least three loci. The genetic similarity between theD. simulans/D.mauritianaandD. simulans/D.sechelliahybridizations probably results from independent evolution and not phylogenetic artifacts, because the dominance relationships and behavioural interactions differ between the two hybridizations. The lack of an X-chromosome effect on sexual isolation contrasts with genetic studies of post-zygotic reproductive isolation, which invariably show strong effects of this chromosome.