Land molluscs of Zanzibar Island (Unguja), Tanzania, including a new species of Gulella (Pulmonata: Streptaxidae)

The land molluscs of Zanzibar island (Unguja), Tanzania are reviewed based on a) published records and b) a quantatitive survey undertaken at Jozani Forest, Unguja in 2000. 58 species are recorded from Unguja, including 716 new records and a new species of Gulella (Pulmonata: Streptaxidae). Two E. African species and one Aldabran species are placed in synonymy. The resulting annotated checklist allows a comparison of the Unguja fauna with that of other parts of E. Africa and more oceanic Indian Ocean islands. Only three additional taxa are yet recorded from the other major Tanzanian coastal islands, Pemba and Mafia. Of the 61 species, seven (11%) are putative endemics for Unguja and/or Pemba/Mafia, 14 (23%) show coastal E. African distributions, 24 (39%) show wider E. African distributions, and 16 (26%) show very wide distributions in which anthropogenic introduction has often played a part. 11(18%) also show affinities with the oceanic Indian Ocean islands; these are briefly discussed. Levels of endemism in Jozani and on Unguja as a whole are comparable to mainland E. African coastal forests that have been subject to similar surveys. Relative to these forests, species richness at Jozani is high (29 species) but variable and skewed towards a few abundant species. Data are provided on a further 25 species recorded from “Zanzibar” but of dubious localisation or identity, as a reference for future work in the region.