The Drosophila subobscura Adh genomic region contains valuable evolutionary markers.

We have sequenced 4 kb of the genomic region comprising the Adh (Alcohol dehydrogenase) gene of Drosophila subobscura. In agreement with other species which belong to the same subgenus, two structural genes, Adh and Adh-dup, are contained in this region. The main features of these two genes of D. subobscura have been inferred from the sequence data and compared with the homologous region of D. ambigua and D. pseudoobscura. Drosophila subobscura Adh and Adh-dup differ from those of D. ambigua at a corrected estimation of 10.1% and 12.5%, respectively, while from those of D. pseudoobscura they differ by 9.5% and 8.1%, respectively. Our data suggest that Adh and Adh-dup are evolving independently, showing a species-specific pattern. Moreover, particular features of some regions of these genes make them valuable evolutionary hallmarks. For instance, replacement substitutions in the third exon of Adh may indicate the branching of the melanogaster-obscura groups, whereas replacement substitutions in the third exon of the Adh-dup could be used to assess speciation within the obscura group.