The land snail fauna of a square kilometer patch of rainforest in southwestern Cameroon, high species richness, low abundance and seasonal fluctuations

Systematic sampling of a single square km patch of rather acidic, undisturb ed, fairly uniform Cameroonian rainforest during two different rainy season s yielded 97 species of land snails, belonging to at least 12 families. Up to 45 species were collected within a single sampling site of 20 m x 20 m d uring a single visit, and up to 51 during two visits in different seasons. This might be the world's highest sympatric land snail diversity reported t o date, Variation in species composition among the sampling sites appeared to be largely random, and not due to geographic or ecological replacement. Three (super) families make up 86% of the species, the carnivorous Streptax idae (34%) being the most diverse. Overall snail abundance was rather low, and many species were rare. Of 64% of the species, the abundance was less t han 1% of all specimens (2,654) collected. A substantial difference was obs erved in overall snail abundance between the two sampling periods. About 27 % of the species were uniquely found in one of the two sampling periods, an d many species differed more than 50% in relative abundance between these s easons. At least 27% of the species were largely or completely arboreal, an d 19% were found to live both on the ground and in the vegetation; 46% of t he species appear to be confined to the ground, and of 7% insufficient info rmation was available. Major adult shell dimensions (height or diameter) ra nge between approximately 1 and 165 mm, but the vast majority (74%) of spec ies has adult shells smaller than 10 mm. The shell height:diameter ratio di stribution is bimodal, but differs from those previously reported for other faunas by relatively many "globose" (H/D 0.8-1.2) and very tall (H/D 2.8-4 .4) shells. The distribution of neither shell size nor shell shape differed between ground-dwelling and (partly) arboreal species.