The purpose of the proposed research is to identify the number and locations of genetic factors underlying differences in adult male genital morphology in the Drosophila melanogaster species subgroup. The approach will involve labeling individual genomic segments of the mauritiana genome with a P-element construct containing an eye- color marker. The study will also be aided by the use of molecular markers. We propose a program of hybridization with simulans followed by repeated backcrossing to create a large number of simulans strains each true-breeding for a separate introgressed segment to the mauritiana genome. These strains will be analyzed for characters of the male genitalia which differ of these characters. Knowledge of the number of genetic factors that underlie genitalic differentiation between closely related species is crucial to our understanding of this widespread phenomenon, especially in the construction of evolutionary models to account for it. Additional aspects of the study will address whether the effects of the introgressed loci show additivity or dominance, and the degree to which these loci interact epistatically to produce this divergent morphology.
