Phylogeography of the intertidal marine bivalve Lasaea hinemoa (Mollusca: Bivalvia) in New Zealand

Genetic investigations of members of the bivalve genus Lasaea have revealed unexpected diversity in the genus, as well as close affiliations between geographically distant populations. Here we investigate the phylogeography of the New Zealand species L. hinemoa using mitochondrial and nuclear gene sequences (cytochrome c oxidase subunit III and Internal Transcribed Spacer 2, respectively) from populations around the country. Additionally, we designed novel microsatellite markers, which enabled us to check the specific species status implied by the two single-gene markers. Lasaea hinemoa individuals fell into four clades. Clades I and III were numerically dominant, with a suggestion of some biogeographic structure around the coasts of mainland New Zealand, and we argue they represent separate cryptic species. Samples from the subantarctic Antipodes Island contained individuals from two clades (I and II). The latter clade is close to populations from the Kerguelen Islands, which suggests possible transoceanic dispersal via the Antarctic Circumpolar Current. Clade IV, represented by small numbers of individuals from Picton and Mahia, appears to be the result of transoceanic dispersal by yet another Lasaea species.