Chromosomal phylogeny of the Drosophila fasciola species subgroup revisited (Diptera, Drosophilidae)

Abstract

The analysis of polytene chromosomes in 26 strains of seven species in the Drosophila fasciola subgroup, from several locations in Brazil, in addition to strains of two species belonging to the Drosophila mulleri subgroup (D. aldrichi and D. mulleri), enabled us to determine that the 3c inversion found in the latter species differ in one of its break points from that present in the species of the fasciola subgroup. Therefore, a change in the mulleri complex denomination from inversion 3c to inversion 3u is proposed. Accordingly, the fasciola subgroup is no longer a lesser phylogenetic part within the mulleri subgroup. Rather, it is directly related to the likely ancestor of the repleta group, called Primitive I. This information removes the main obstacle to considering the Drosophila fasciola subgroup as an ancestral group within the Drosophila repleta species group, according to the hypothesis of Throckmorton. Our data also support the conclusion that D. onca and D. carolinae are closely related species based on one new inversion in chromosome 4 (4f²), in both species. D. fascioloides and D. ellisoni also form a pair of sister species based on the presence of fusions of chromosomes 2-4 and 3-5. D. rosinae is related only to the likely ancestor of the fasciola subgroup, where the 3c inversion was fixed.