Land snails on islands: building a global inventory

Abstract

Land snails are one of the most diverse groups of terrestrial animals and are commonly used as model organisms in ecology, biogeography and conservation biology. Despite being poor dispersers, they form crucial components of island faunas and exhibit high percentages of endemism. Insular land snails are also among the most threatened animals on Earth, already having suffered extensive human-caused extinctions. However, current estimates of global insular land snail diversity are based on sporadic records published at the scale of individual islands and/or archipelagos. To tackle this shortfall, we herein present the major features of a global inventory of island snails. We recovered full species lists from existing literature and available species checklists for 727 islands across the globe and collated a database which currently includes the occurrence of 11,139 species, that is approximately 48% of all known land snail species (of which there are an estimated 23,000). Seventy-five percent of the species are single-island endemics, underlining the exceptional nature of islands as global biodiversity hotspots. Overall, our attempt is one of few to examine insular invertebrate diversity at coarser scales and a crucial step to the study of global patterns in island biodiversity.