Rissooidean freshwater gastropods from the Vanuatu archipelago

During expeditions to Santo and the Torres islands belonging to the Vanuatu archipelago in 2006 and 2007, ten new species of tateid gastropods confined to springs, the upper most, slowly flowing regions of streams or the groundwater had been discovered. These species were now described based on shell morphology and anatomy. In accordance with geography, these characters placed the species from Vanuatu between those from New Caledonia and Fiji, suggesting a stepping stone-like dispersal across the Pacific with an origin in New Zealand and the far end on the Austral islands. We also assessed the threat status of the new species according to the IUCN Red List criteria and concluded that they should be amended by explicit incorporation of the scale of potential human impact or stochastic natural events relative to the size of the habitat of organisms. © Springer Science+Business Media B.V. 2009.