Subfossil Land Snails from Easter Island, Including Hotumatua anakenana, New Genus and Species (Pulmonata: Achatinellidae).

Abstract

The depauperate modern terrestrial biota of Easter Island contrasts with that of most other southeastern Polynesian high islands, which characteristically support a number of endemic species of insects, land snails, birds, and plants. We investigated cultural and noncultural late Holocene deposits at Anakena, Easter Island, establishing the former presence of endemic land snails on the island. These include an unidentified helicinid, a Nesopupa species, and a previously undescribed extinct achatinellid land snail, Hotumatua anakenana Kirch, Christensen & Steadman, n. genus and n. sp. A human-introduced achatinellid, Pacificella variabilis, occurs in later stratigraphic contexts of the same site. Prehistoric deforestation may have been the primary cause of the extinction of Hotumatua, although predation by rats or other alien species may have been involved as well. Along with recently discovered extirpated species of angiosperms, seabirds, and land birds, the extinction of Hotumatua reflects the nearly complete loss of the native biota of Easter Island after Polynesian colonization about 1,000 yr ago.