The phylogeny of humpback dolphins genus Sousa

The relationships within the genus Sousa presented here show clear differences and similarities between regions, which are contradictory to the complex morphological patterns of the genus (Ross et al. 1996). Chinese and east Australian animals display similarities in colour and fin shape, but are divergent in their mtDNA. In dolphins from Australian waters the tympanoperiotic bones are of the chinensis form, while in dolphins from South Africa, the tympanoperiotics are of the plumbea form -yet their mtDNA haplotype pattern is exactly opposite. Tympanoperiotic bones in dolphins from India matched the plumbea form, while the Indonesian (borneensis) animal used in this study (S. chinensis) resembled the chinensis form in three of five tympanoperiotic bone characters. The complex morphological relationships within the genus Sousa are reviewed in Ross et al. (1996). In addition, humpback dolphins seem to display strict female philopatry (Goodwin, 1997). This may have prevented the historically recent dispersal of mtDNA haplotypes. The corollary of this, predominantly male dispersal, may have caused the intergradation and exchange of contemporary morphological characters. The phylogeny presented here supports the inclusion of the Indonesian (Bornean -borneensis ‘ plumbea) specimen in chinensis and the northern Indian Ocean sample (co-type) in plumbea (Ross et al. 1996). But, it places haplotypes from south east Africa with those from Hong Kong and Indonesia and places the plumbea co-type from India with those from Australia. This is puzzling, and contrary to the currently held opinion that Pacific humpback dolphins are represented by the chinensis form and are distinct from Indian Ocean Sousa, represented by the plumbea form (Zhou Kaiya et aI., 1980; Ross, 1984).