Phylogenetic reconstruction of the Drosophila obscura group, on the basis of mitochondrial DNA

We have constructed restriction-site maps of the mtDNAs in 13 species andone subspecies of the Drosophila obscura group. The traditional division ofthis group into two subgroups (affinis and obscura) does not correspond tothe phylogeny of the group, which shows two well- defined clusters (theNearctic affinis and pseudoobscura subgroups) plus a very heterogeneous setof anciently diverged species (the Palearctic obscura subgroup). The mtDNAof Drosophila exhibits a tendency to evolve toward high A+T values. Thisleads to a "saturation" effect that (1) begets an apparent decrease in therate of evolution as the time since the divergence of taxa increases and(2) reduces the value that mtDNA restriction analysis has for thephylogenetic reconstruction of Drosophila species that are not closelyrelated.