Characterization and evolution of the Adh genomic region in Drosophila guanche and Drosophila madeirensis.

We have sequenced the genomic region of the Adh (alcohol dehydrogenase) gene of Drosophila guanche and Drosophila madeirensis. Two genes, Adh and Adh-dup, whose main features are shared by other Drosophila species, are contained in this region. Interspecies comparisons of this genomic region of these two species with the region in D. subobscura have been made. Our data are in agreement with the phylogenetic relationship of the three species and particularly with the very close proximity of D. madeirensis and D. subobscura. The correct alignment of the noncoding as well as the coding sequences allows us to infer how this region has evolved. The degree of divergence of D. madeirensis and D. subobscura Adh sequences is low and replacement substitutions are as frequent as silent substitutions. In addition, heterogeneous divergence rates for coding and noncoding sequences have been observed. Our data also reveal that a recent evolutionary event is responsible for the branching of the three species.