The coastal molluscan fauna of the northern Kermadec Islands, Southwest Pacific Ocean

Abstract

A total of 358 species of molluscs (excluding pelagic species) is recorded here from coastal marine habitats around the northern Kermadec Islands. The fauna is dominated by species that are widely distributed in the tropical western and central Pacific Ocean. The majority of these are restricted to the tropics and subtropics, but some range south to temperate latitudes. Sixty‐eight species, comprising 19% of the fauna, are thought to be endemic to the Kermadec Islands. That group includes several species that have an in situ fossil record extending back to the Pleistocene. The fauna also includes a number of non‐endemic species that are restricted to subtropical or subtropical‐temperate latitudes in the southern Pacific Ocean. Some of these are restricted to the southwestern Pacific, others are shared with subtropical central and eastern Pacific islands. The Kermadec Islands’ coastal molluscan fauna is depauperate at the species/genus level in comparison with faunas in the tropical western and central Pacific Ocean, and is less diverse than the subtropical south Pacific faunas of Lord Howe, Norfolk and Pitcairn islands. The species composition of the Kermadec molluscan fauna in part reflects the present‐day biogeographic isolation of the islands, their subtropical location and the small range of habitat types present. It is also an inheritance of a geological and paleo‐oceanographic history that gave rise to faunal turnover and allopatric speciation.