| Most cetologists consider the genus Tursiops, bottlenose dolphins, to be comprised of one species, Tursiops truncatus (Montagu, 1821), which is distributed worldwide in tropical and temperate waters. However, marked geographic variation among bottlenose dolphins--in particular, morphological variation between inshore and offshore animals--has contributed to uncertainties regarding stock structure and taxonomy within the genus. Stock delineations are necessary to assess the impacts of die-off and fishery mortalities on bottlenose stocks, and to conserve population units.; One hundred and twenty-seven mitochondrial DNA control region sequences (402bp) were used to investigate intra- and interspecific differences among bottlenose dolphins in a worldwide context. Seventy-three haplotypes were identified. Two fixed and three frequency nucleotide substitutions were present between inshore bottlenose dolphin haplotypes from the western North Atlantic Ocean/Gulf of Mexico and offshore bottlenose dolphin haplotypes from all ocean basins (western North Atlantic and Gulf of Mexico, eastern and western Pacific, and Indian Oceans). Parsimony analyses revealed the monophyly of inshore bottlenose dolphins from the western North Atlantic Ocean and Gulf of Mexico, but relationships among offshore bottlenose dolphins were unresolved. These results, combined with information on morphology and ecology, supported the suggestion that there are species-level differences between inshore and offshore bottlenose dolphins in the western North Atlantic/Gulf of Mexico.; To investigate the phylogenetic relationship of the nominal species Tursiops aduncus to Tursiops truncatus, I sequenced a portion of the control region in sixty-eight individuals. There were one fixed and two frequency nucleotide differences between Tursiops aduncus and Tursiops truncatus datasets. Parsimony analysis indicated the separation of Tursiops aduncus and Tursiops truncatus into two clades. Parsimony analysis also was used to examine the relationships of Tursiops aduncus and Tursiops truncatus to six other delphinine species (Stenella attenuata, Stenella longirostris, Stenella coeruleoalba, Stenella frontalis, Stenella clymene, and Delphinus delphis). A bootstrap consensus tree reflected results similar to those of analyses based on the mitochondrial DNA cytochrome b gene. Tursiops aduncus was not a sister group to Tursiops truncatus. Evidence from non-maternal genetic markers and morphological investigations throughout the distribution of the genus Tursiops may provide further support to identify separate species. |
