Phylogenetic relationships among species groups of the virilis-repleta radiation of Drosophila.

r nae is the virilis–repleta radiation, as evaluated by the umber of species and species groups (Throckmorton, 962, 1975). The virilis and repleta species groups have een extensively used as model systems in the studies f mechanisms of speciation, mapping genes, and chroosomal rearrangements (Patterson and Stone, 1952; owell, 1997). Drosophila virilis is a prominent refernce species for comparison with D. melanogaster in regard to patterns and mechanisms of molecular and genomic evolution (Nurminsky et al., 1996; Hartl and ozovskaya, 1995). The Drosophila repleta group ithin this radiation is potentially very promising for he study of speciation mechanisms, because it dislays a range of different degrees of reproductive isoation among its members (Patterson and Stone, 1952). t also provides an example of a very rapid and sucessful radiation in the deserts. The phylogenetic relationships of species groups in he virilis–repleta radiation are largely unresolved in hrockmorton’s classifications. Moreover, there are ome discrepancies between his earlier (1962) and ater (1975) schemes. Improvement in the understandng of the phylogenetic relationships among the species roups and subgroups of the virilis–repleta radiation as come from cytological studies (reviewed in Wasseran, 1982, 1992; Powell, 1997), but there were few olecular studies considering intergroup and subroup relationships of the radiation. In a study based n 28S rRNA genes, Pélandakis and Solignac (1993) ncluded representatives of many groups of the virilis– epleta radiation. With the exception of D. polychaeta, hese groups form a monophyletic lineage, but with low ootstrap support (less than 50%) for the clade as a hole and for the relationships among species groups. ecently, Durando et al. (2000) have conducted a deailed phylogenetic analysis of the repleta species roup, which also includes three other groups of the