Phylogenetic Relationships Among Eastern Pacific Common Dolphins (Delphinus spp.)

Common dolphins in the eastern Pacific are currently recognized as separate subspecies, a long-beaked form (Delphinus delphis bairdii) and a short-beaked form (Delphinus delphis delphis), which are sympatric across portions of their ranges in waters off California. While the taxonomic status of these forms is still unclear, several studies have shown that they represent different evolutionary trajectories. Most of this work has been conducted on common dolphins in the Eastern North Pacific. In this study, the phylogenetic relationship of these two forms was examined, in addition to long-beaked common dolphins occurring off Peru in the Eastern South Pacific, using complete mitochondrial genomes. Peruvian and Californian long-beaked common dolphins formed a monophyletic clade with respect to short-beaked common dolphins from California and common dolphins from Senegal and the Black Sea. This clade of eastern Pacific long-beaked common dolphins was estimated to have zero connectivity with the Californian short-beaked form. Within the long-beaked clade, Peruvian long-beaked common dolphins were monophyletic, although Californian long-beaked dolphins were paraphyletic. These results are consistent with long-beaked common dolphins in the eastern Pacific being a species distinct from short-beaked common dolphins in the same region. Furthermore, evidence showed that Peruvian long-beaked common dolphins may represent a separate subspecies.