New African species in the Drosophila obscura species group: genetic variation, differentiation and evolution

Abstract

The Drosophila obscura species group was known in the Afrotropical region from a single species, D. microlabis. This species was recently rediscovered in Kenya in addition to the discovery of three new obscura group species: D. kirumensis, D. cariouae and D. krimbasi. The patterns of allozyme variation in two African species, D. microlabis and D. kitumensis is compared to that of nine species of the obscura group. Genetic distances have been estimated from allelic frequencies at 35 loci and phylogenies inferred by methods assuming both constant as well as variable evolutionary rates. D. microlabis and D. kitumensis are evolutionary related and close to the Palearctic D. tristis and D. ambigua even if relatively distant. The data support Lakovaara and Saura's hypothesis recognising three species subgroups within the obscura group. In addition, we propose a fourth one for the new African species, the microlabis species subgroup.

The phylogeny of nine species of the Drosophila obscura group inferred by the banding homologies of the chromosomal regions. IV. Element C

“…A similar disposition is also found in Loukas et al (1984). The tree of Cariou et al (1988) groups together all species of the subobscura cluster, but not in the right order; the position of the African species is between the branches of D. tristis and D. ambigua. D. tristis is the one closely related to D. obscura and this last is directly connected to the subobscura cluster.…”

Reevaluation of Phylogeny in the Drosophila obscura Species Group Based on Combined Analysis of Nucleotide Sequences

“…This microlabis-subobscura clade is nested within a larger Old World clade, which contains the remaining species placed in the obscura subgroup. Support for this hypothesis comes from biogeographic information (Throckmorton, 1975), previous morphological and molecular studies (Lakovaara and Saura, 1982;Cariou et al, 1988;Ruttkay et al, 1992), and cladistic analyses (Fig. 6 and data not shown).…”

“…The common ancestor of these species groups likely colonized the western Nearctic region prior to mid-Miocene times, approximately 20 million years ago (Throckmorton, 1975). Recent expeditions in sub-Saharan Africa (Tsacas et al, 1985;Cariou et al, 1988) have discovered an additional subgroup, microlabis, which is found exclusively in the Afrotropical region (Fig. 1C).…”

Differences in gene activity in a Drosophila species cluster belonging to the Obscura group

“…Drosophila subobscura, D. guanche and D. madeirensis are closely related species that form a cluster which differs from the other Drosophila species of the obscura group Cariou et al, 1988;Brehm & Krimbas, 1990;Gonzalez et al, 1990). In a previous work (Moltó et al, 1988) we compared the gene activity of D. subobscura and D. guanche throughout pre-pupal development, establishing that the latter species is less active.…”