A MOLECULAR PHYLOGENY OF THE DROSOPHILA WILLISTONI GROUP: CONFLICTS BETWEEN SPECIES CONCEPTS?

The six sibling species of the Neotropical Drosophila willistoni group have a long history in studies of evolutionary biology, yet to date only one molecular study, which used allozymes, has been published on the phylogeny of the group. Here we present a phylogeny of the siblings based on the sequences of two nuclear genes, period (per) and Alcohol dehydrogenase (Adh), as well as the mitochondrial gene Cytochrome oxidase I (COI). Taken individually, only per has a strong phylogenetic signal supporting a well-resolved phylogeny of the group, and this phylogeny is different from that obtained using allozymes. The COI dataset by itself produces trees that disagree with per, and neither that data nor the Adh data have a strong phylogenetic signal, as indicated by low bootstrap values for all analyses. Combining the Adh and COI datasets results in the same tree as per alone. Combining all three genes results in the same topology, which is strongly supported. Two problematic taxa, D. pavlovskiana and a “Carmody strain,” which were identified as potentially separate species based on reproductive isolation, clearly cluster in the phylogenetic analyses within D. paulistorum and D. equinoxialis, respectively. Thus, there appears to be a conflict between the biological species concept and the phylogenetic species concept.