Character congruence of multiple data partitions and the origin of the Hawaiian Drosophilidae.

We address two systematic questions, the origin and monophyly of the Hawaiian Drosophilidae and the question of how to analyze multiple data partitions containing disparate kinds of information, in this study. New evidence, from analysis of characters from morphology, mitochondrial DNA, and nuclear DNA suggests that the Hawaiian Drosophilidae are a monophyletic assemblage. Although we are not able to suggest a single species group which may represent the continental sister taxon to the Hawaiian Drosophilidae, the candidates suggested by our analysis, the melanicarobusta lineage and the virilis-repleta lineage, have been suggested by other investigators as probable sister taxa. Through analyses of our data partitions separately and in a variety of combinations, we conclude that the best phylogenetic hypothesis to be generated from multiple data partitions will be obtained if the data from these partitions are combined and analyzed simultaneously. We advocate performing tests for congruence between and among data partitions not to justify keeping them apart, but for understanding the interactions among the signals included in the analysis and how they affect the topology of, and support for, the total evidence tree.