Application of Mitochondrial DNA Sequences in the Species Identification of Common Dolphins (Genus Delphinus) in Chinese Waters

Common dolphins, genus Delphinus, are regarded to be composed of two species, i.e., long-beaked common dolphins (D. capensis) and short-beaked common dolphins ( D. delphis). However, the taxanomic status of Chinese common dolphins is still uncertain up to date. In this study, 366 base pairs (bp) of mitochondrial DNA (mtDNA) control region and 336 bp of mitochondrial cytochrome b (cyt b) gene from 12 common dolphins collected in Chinese waters were sequenced and combined with previously published homologous sequences of common dolphins from the Eastern Pacific waters, to address the systematic status and patterns of genetic variation of common dolphins in Chinese waters. Sequence comparison showed that the Chinese common dolphins share the same diagnostic site with recognized long-beaked common dolphins from the Eastern Pacific waters. The sequence divergence between haplotypes from Chinese common dolphins and long-beaked dolphins was much lower than that from short-beaked common dolphins. Phylogenetic tree reconstructed by using neighbor-joining algorithm implemented in the computer software MEGA (molecular evolutionary genetic analysis) version 2.0 found a monophyletic clade including Chinese common dolphins and long-beaked common dolphins, suggesting a relatively close relationship between them. Therefore, the Chinese common dolphins should be referred to as long-beaked common dolphins, Delphinus capensis.