Mitochondrial DNA analysis of sympatric morphotypes of bottlenose dolphins(genus : Tursiops) in Chinese waters

The classification within the bottlenose dolphin (genus Tursiops) is contro versial. Although many morphological variants exist, most authors have conc luded that the genus is composed of a single species, Tursiops truncatus (M ontagu 1821). Two distinct morphotypes of bottlenose dolphins, which have b een referred to as T. truncatus and T. aduncus, exist in sympatry in Chines e waters. Comparisons of a 386-bp fragment of the mitochondrial DNA (mtDNA) control region (n = 47) indicated that the two sympatric morphotypes were genetically distinct, with seven fixed site differences and a sequence dive rgence of approximately 4.4%. Phylogenetic analyses using maximum likelihoo d, neighbour-joining and maximum parsimony approaches showed that the trunc atus-type dolphins from Chinese waters were more closely related to Atlanti c Ocean truncatus-type than to the sympatric aduncus-type dolphins. The Atl antic truncatus-type dolphins also shared the same diagnostic sites that se parated Chinese truncatus-type from aduncus-type dolphins. The molecular da ta agreed completely with the morphological classifications of the specimen s. This congruence is strong evidence that the sympatric morphotypes in Chi nese waters are reproductively isolated and comprise two distinct species. These findings have important implications for the conservation of bottleno se dolphins in Chinese waters.