Conservation biogeography of terrestrial molluscs on tropical limestone karsts

Abstract

In the first chapter, I perform a literature review to show that limestone karsts are considered a??arksa?? of biodiversity and elaborate on their importance to humanity and increasingly threatened status. Although karsts require greater protection due to their high levels of endemism, reserve location is not always performed within a scientific framework. Conservation planners must incorporate biogeographical patterns of karst- endemic species into their decision making processes, but such information is severely lacking. In the second chapter, I identify biogeographical variables (i.e., karst area, isolation, surrounding soil type and geological age) hypothesised to correlate with endemic richness of terrestrial molluscs on karsts, and investigate molluscan species compositional trends across karsts in two different biogeographical regions: Peninsular Malaysia and Sabah. Generalized linear mixed-effect models revealed an important contribution of karst area and surrounding soil type on molluscan endemic richness, while non-metric multidimensional scaling showed that karsts separated by vicariant barriers in different parts of Peninsular Malaysia and Sabah had distinct malacofaunas. In Malaysia, large karsts surrounded by podzolic soils within biogeographically distinct groups of karsts should therefore be conserved to maximise the protection of endemic molluscs. Having identified karst area as an important predictor of endemic richness, I utilized this information to create irreplaceability and vulnerability maps for karsts in the final chapter. These maps indicated that 10 out of 62 karsts in Peninsular Malaysia should be prioritized for conservation. In addition, I discuss how regional karst conservation initiatives are complicated by issues such as resource shortages, ad-hoc conservation planning, inadequate protective measures and deficient baseline data.