Hierarchical structure in the Drosophila mojavensis cluster (Diptera: Drosophilidae).

Sequences from three gene regions from the nuclear and mitochondrial genomes were used to examine the extent and nature of hierarchical structure in the Drosophilamojavensis cluster (Drosophila arizonae, D. mojavensis and D. navojoa) of the D. repleta species group. To determine the genetic divergence of these three species, sequence data were analyzed using maximum parsimony and population aggregation analysis. Individual and combined gene genealogies indicate that D. arizonae and D. mojavensis are neither diagnosable nor monophyletic with respect to one another. Although D. navojoa has differentiated from D. arizonae and D. mojavensis, as diagnosed by nuclear gene sequences, it may have undergone a reticulation event with D. arizonae. Our results suggest that either these taxa are still undergoing differentiation at the molecular level or have experienced gene flow in the recent past.