Russo CA, Takezaki N, Nei M.

Mol Biol Evol. 1995 May;12(3):391-404 doi:10.1093/oxfordjournals.molbev.a040214

Molecular phylogeny and divergence times of drosophilid species.

Study of Adh genes, nuclear 18S rRNA and mitochondrial DNA suggests that D. mel and D. pseudoobscura diverged 24.9 +/- 2.88 My ago, based on the assumption that D. picticornis and D. silvestris diverged 5.1 My ago.