Genetic assessment of population boundaries and gene exchange in Hector's dolphin

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Summary

A genetic assessment of local population structure and dispersal rates in Hector's dolphin (Cephalorhynchus hectori) is presented as an aid to conservation managemetnt of this endangered endemic cetacean. The results confirm previous genetic analyses of mtDNA population structure showing the presence of four regional populations-North Island, East Coast South Island, West Coast South Island, and South Coast South Island- that are connected by little or no female dispersal.

It was demonstrated that the local populations within regions were connected by gene flow only with immediately adjacent populations (fitting a one-dimensional stepping-stone model) while the relationship of sub-populations between the regions was more consistent with a complete isolation model, equivalent to geographic barriers. A measure of expected mtDNA diversity suggested decline in eight of the ten local populations. Microsatellite heterozygosity was also lower than expected in the East Coast South Island and North Island regions, suggesting further regional sub-structuring, or loss of diversity due to population decline. The possibility of male-mediated gene flow and estimates of local inbreeding require further investigation.