MOLECULAR SYSTEMATICS OF RIVER DOLPHINS INFERRED FROM COMPLETE MITOCHONDRIAL CYTOCHROME-B GENE SEQUENCES

1,140 bp of the complete mitochondrial cytochrome- b gene sequences of baiji ( Lipotes vexillifer ), franciscana ( Pontoporia blainvillei ), and Ganges river dolphin ( Platanista gangetica gangetica ) were determined to address the systematic position and phylogeny of extant river dolphins with combination of homologous sequences of other cetaceans. The neighbor-joining (NJ), maximum parsimony (MP), and maximum likelihood (ML) phylogenetic analyses all identified the river dolphins into three lineages, i. e., Platanista, Lipotes , and Inia + Pontoporia . The Lipotes did not have sister relationship with either Platanista or Inia + Pontoporia , which strongly supported the referral of Lipotes to a separate family, i. e. , Lipotidae. There were very high sequence divergences between all river dolphin genera, suggesting a relatively longer period of separation time than those among other odontocete families.