Molecular phylogenetics and biogeography of the nacellid limpets of New Zealand (Mollusca: Patellogastropoda).

The origin and radiation of nacellid limpets (genera, Cellana and Nacella) are not well-resolved, but fossil records provide evidence of a historical range spanning throughout the PaciWc, including North America (Lindberg and Hickman, 1986) north and south Australia, New Zealand, Java, Chile, and east and west Antarctica (Powell, 1973). The modern biogeographic range of Cellana is mostly tropical, extending north to Japan, East to Juan Fernandez and Hawaii, south to South Africa, Madagascar, south east Australia, New Zealand and the sub-Antarctic Islands, where it co-exists on Campbell Island with the sister taxon Nacella (Powell, 1973). Nacella is restricted to the sub-Antarctic and Megallenic region (Powell, 1973). Molecular phylogenetic studies of Patellogastropods (Koufopanou et al., 1999; Nakano and Ozawa, 2004) have conWrmed the monophyletic grouping of the Nacellidae limpets relative to the sister taxon Patellidae. The Nacellidae classiWcation was Wrst proposed in 1975 by Golikov and Starobogatov (1975), but was not widely accepted until Lindberg and Hickman (1986) conWrmed the familial split through shell microstructure analysis. New Zealand species of Cellana represent the southern most limits of the genus range (Powell, 1973) and are geographically placed between two potential sources of species immigrants: the tropics and the sub-Antarctics. Two species, Cellana ornata and Cellana radians, are distributed around the entire coastline of New Zealand. Cellana Xava and Cellana denticulata are restricted to the north east coast while Cellana strigilis redimiculum is restricted to the south east. Cellana stellifera is the only sub-tidal species of this