Geographic isolation of Hector's dolphin populations described by mitochondrial DNA sequences

To describe the genetic structure of Hector's dolphin (Cephalorhynchus hectori) populations, we used the polymerase chain reaction to amplify and sequence a 360 base-pair fragment of the mitochondrial DNA control region from 34 beachcast or gillnet-caught specimens. Variation in these sequences identified 11 distinct haplotypes differing from one another by 0.28-1.67% and by an average of 4.47% from the closely related Commerson's dolphin. The genealogical relationship of these haplotypes showed a strong concordance with the geographic origins of the samples. An analysis of variance modified for molecular data showed that 74% of the sequence variation could be explained by the three primary sampling regions: the North Island, the west coast of the South Island, an dth east coast of the South Island. Such a marked segregation of maternal lineages across a small geographic range is unusual among cetaceans. The low rate of female dispersal, as indicated by this mitochondrial DNA structure, could increase the vulnerability of local populations to extinction due to fisheries-related mortality.