Phylogenetic relationships and population structure among humpback dolphins based on mtDNA variation

The taxonomy, systematic relationships, and population structure of humpback dolphins (genus Sousa) have been controversial. Various nominal species have been described or subsumed. Recent reports have suggested the division of Sousa into one to three distinct species or sub-species. However, many of these analyses have not been conducted in a proper systematics framework, did not include all representative putative taxa or were lacking specimens from parts oftheir geographic range, and have not been in published in peer-reviewed journals (typically necessary for revising taxonomy). In order to address relationships and taxonomic status among Sousa species, we present a preliminary genetic analysis of humpback dolphins primarily from Southeast Asia, the coast of Oman, and South Africa. A total of 110 samples were sequenced for 501 bp of mtDNA control region and significant population structuring at the regional level was revealed. Population aggregation and phylogenetic analyses ofmtDNA control region lineages and a subset of lineages analyzed for a 358 bp fragment of Cytochrome B revealed a series of complex relationships among humpback dolphins in the Indian and Pacific Oceans. These preliminary data are a critical first step to better understanding the taxonomy and systematics in the genus Sousa. Additional molecular character data from other mitochondrial and nuclear genes will be essential for resolving relationship and taxonomic status for humpback dolphins.