| The Old World fruit-bat genus Dobsonia includes approximately 13 species distributed throughout the islands of the southwest Pacific, from the Philippines to the Solomons, as well as northeastern Australia. The species have been divided into four "natural groups" distinguished by anatomical differences. I constructed a molecular phylogeny from mitochondrial cytochrome b sequences which, in conjunction with analyses of an expanded collection of anatomical data, was employed to explore the character-evolution and taxonomic validity of these groups and their constituent taxa. The dated molecular phylogeny was then used to infer the influence of the region's geologic history on the diversification of Dobsonia species and their current distributions.; The phylogenetic trees corroborate Aproteles' position as the sister-genus of Dobsonia, but neither the monophyly of the morphologically defined D. VIRIDIS and D. MOLUCCENSIS "natural groups" nor the species-rank of D. magna are supported. Distinct haplotypes from Sulawesian populations suggest the sympatric occurrence of D. viridis and D. exoleta on Kabaena, and provide further evidence for a distinct subgroup of D. viridis (perhaps crenulata).; Morphological analyses indicate that the "natural groups" differ significantly in greatest skull length, as do the species of most sympatric pairs, the first component in principal-components analysis (measures of skull size) capturing 94.5% of the variability within the cranial data set. Relatively little variability was accounted for by differences in skull shape.; My review of the literature suggests that the primary determinant of resource partitioning between sympatric Dobsonia species is day-roost habitat together with social structure (colonial cave-roosting vs. small-group foliage-roosting), which may be correlated with spatial dispersion of food resources, in turn relating to body-size differences via the energetic costs of commuting distances. Although my work provides some evidence of species diversification reflective of ecological pressures, the relationships among geologic and phylogenetic events indicate that the exceptionally dynamic geologic history of the islands inhabited by Dobsonia has been at least as important as biological interactions in the diversification of genus. |
