Abstract
Limpets of the genus Cellana are important grazers in the intertidal zone throughout New Zealand and in many ways serve as models for understanding biogeographic patterns along heterogeneous coastlines. This genus is speciose in New Zealand, with some being widely distributed. The C. strigilis species complex in particular provides a good model for population connectivity because it is spread over the southern coast of New Zealand and throughout the Sub-Antarctic Islands, a region of complex hydrography from around 45 degrees to 52 degrees south latitude. In the present study we investigated genetic connectivity and phylogeographic structure of the C. strigilis complex from mainland New Zealand, the Chatham Islands and the Sub-Antarctic Islands using mitochondrial gene sequence data. Partial sequences from mitochondrial cytochrome b, 12S and 16S genes revealed 2 genetic lineages that separate the Chatham, Bounty and Antipodes Island populations from the New Zealand mainland, Auckland and Campbell Island populations. Application of a relaxed molecular clock suggests that these lineages diverged 2 to 5 million years ago. The genetic homogeneity observed among populations of the 2 lineages, in conjunction with larval modelling, suggests that these populations are presently isolated but may have been colonised through long-distance dispersal from the southern island populations within the last 100 000 yr. Alternatively, the lack of genetic differentiation may suggest that the populations experience ongoing bottleneck effects.