Organisms
Research Projects	Research Group	Organisms	Collection	DNA Labs
The land snails of Sabah The East-Malaysian state of Sabah (formerly North-Borneo) supports a rich and diverse land snail fauna. The current grand total for the state is c. 270 species. Many of these are small species known primarily from limestone outcrops. The most prominent among these are the bizarre snails of the genus Opisthostoma. The species of its subgenus Plectostoma are not only extremely numerous on limestone outcrops, but also obligately calcicolous, that is: they cannot live on non-limestone soils. As a result, many species are restricted to just a single outcrop, and the same appears to apply to certain other species of the same family, the Diplommatinidae, as well. For this reason, 18 of these species were recently placed on the IUCN Red List. Nine species of Bornean Opisthostoma (subgenus Plectostoma). Drawings: Jaap Vermeulen. Due to the high abundance, diversity, and endemism of land snails on limestone outcrops, malacological work on non-limestone areas has been neglected. My students and I have tried to rectify this situation, by focusing our expeditions largely on underexplored, non-calcareous areas, such as Danum Valley, the Crocker Range, Kinabalu Park, and the Ulu Tungud area. Some of these areas are highly acidic and calcium-poor, and would seem to be very snail-unfriendly areas. Indeed, population densities seem very low. Nevertheless, many new and unexpected taxa have been encountered in these regions, and their species diversities appear to be as high as many limestone hills. A paper describing all (c. 45) new species is currently in preparation. A field guide to the land snails of Sabah is also in preparation and will be published by Natural History Publications (Borneo). It will contain descriptions of snail habitats in Sabah and instructions for the study of land mollusks. All species will be briefly described and illustrated with pencil drawings by Jaap Vermeulen, and photos by Peter Koomen and Menno Schilthuizen. Snail samples taken from plots adjacent to a limestone outcrop (hatched area) do not contain any Plectostoma, whereas species of this subgenus dominate all samples taken from within the limestone area.