Molluscan diversity in the unconserved Vohimena and the conserved Anosy mountain chains, southeast Madagascar Original Research Article

We sampled terrestrial molluscs from replicated, 0.04 ha, altitudinal transects through primary forests on one mountain each in the southern Anosy chain (near Andohahela Reserve) and in the southern and the northern Vohimena chain in southeast Madagascar. Species richness (range 4–23 per sample) was significantly higher on the Vohimena mountains (mean 14.8±0.8) than on the Anosy mountain (mean 10.5±0.7), a difference of 41%. A similarly significant difference (26%) occurred in diversity as measured by the Shannon index. Full distributional data were available for 41 species, all of which meet IUCN criteria as either Critically Endangered (27%), Endangered (68%), or Vulnerable (5%). Species limited to only one of the two mountain chains number 20, of which the Vohimena chain has 17, or 5.7 times as many as the Anosy chain. These results support previous studies and call for conservation and further surveys in the Vohimena chain, which is undergoing increasingly rapid deforestation.