The phylogeny of closely related species as revealed by the genealogy of aspeciation gene, Odysseus

Molecular differentiation between races or closely related species is often incongruent with the reproductive divergence of the taxa of interest. Shar ed ancient polymorphism and/or introgression during secondary contact may b e responsible for the incongruence. At loci contributing to speciation, the se two complications should be minimized (1, 2); hence, their Variation may more faithfully reflect the history of the species' reproductive different iation. In this study, we analyzed DNA polymorphism at the Odysseus (OdsH) locus of hybrid sterility between Drosophila mauritiana and Drosophila simu lans and were able to verify such a prediction. Interestingly, DNA variatio n only a short distance away (1.8 kb) appears not to be influenced by the f orces that shape the recent evolution of the OdsH coding region. This locus thus may represent a test case of inferring phylogeny of Very closely rela ted species.