Mitochondrial DNA evolution in themelanogaster species subgroup ofDrosophila

Abstract

Detailed restriction maps (40 cleavage sites on average) of mitochondrial DNAs (mtDNAs) from the eight species of themelanogaster species subgroup ofDrosophila were established. Comparison of the cleavage sites allowed us to build a phylogenetic tree based on the matrix of nucleotide distances and to select the most parsimonious network. The two methods led to similar results, which were compared with those in the literature obtained from nuclear characters. The three chromosomally homosequential speciesD. simulans, D. mauritiana, andD. sechellia are mitochondrially very related, but exhibit complex phylogenetic relationships.D. melanogaster is their closest relative, and the four species form a monophyletic group (theD. melanogaster complex), which is confirmed by the shared unusual length of their mt genomes (18–19 kb). The other four species of the subgroup (D. yakuba, D. teissieri, D. erecta, andD. orena) are characterized by a much shorter mt genome (16–16.5 kb). The monophyletic character of theD. yakuba complex, however, is questionable. Two species of this complex,D. yakuba andD. teissieri, are mitochondrially indistinguishable (at the level of our investigation) in spite of their noticeable allozymic and chromosomal divergence. Finally, mtDNA distances were compared with the nuclear-DNA distances thus far established. These sequences seem to evolve at rather similar rates, the mtDNA rate being barely double that of nuclear DNA.