Population genetic structure of the Burrunan dolphin (Tursiops australis) in coastal waters of south-eastern Australia: conservation implications

The Burrunan dolphin, Tursiops australis, is a newly described species endemic to southern Australian coastal waters. The current distribution ranges from South Australia, east to Victoria and south to Tasmania. In the eastern region of their range, only two known resident populations of T. australis occur, Port Phillip Bay and the Gippsland Lakes. Little else is known about the population status and migration patterns of the species. Here we examine population genetics of T. australis using ten microsatellite loci and two sequences of mitochondrial DNA, the control region (~450 bp) and cytochrome b (~1,200 bp). A total of 163 T. australis samples were collected from various locations across the Victorian and Tasmanian coastlines. Genetic data showed the highest differentiation between the Port Phillip Bay and both Gippsland Lakes and Tasmanian samples. Network analysis, using concatenated mtDNA sequences, showed geographic segregation and Bayesian analysis, using microsatellite data, also supported the presence of two genetic clusters. Both microsatellite and mtDNA data indicated low genetic diversity when compared to levels reported for other dolphins. Maternal philopatry was suggested for Port Phillip Bay in particular. Our data suggest that T. australis from coastal waters of south-eastern Australia consists of two populations with little or no contemporary gene flow; one occurs in Port Phillip Bay; the second extends from the east coast of Tasmania across Bass Strait to Gippsland Lakes. Tursiops australis appears to be characterised by small, localised, genetically distinct populations and should thus be further assessed under local, national and international threatened species criteria.