The land snail diversity in a square kilometre of tropical rainforest in Okomu Natioal Park, Edo State, Nigeria

The land mollusc fauna in a single square kilometer of undisturbed tropical rainforest in Okomu National Park, Edo State, Nigeria was surveyed by sampling thirty 20-m2 plots. Sampling methods were similar to those used in the rainforests in Cameroon and Sabah. Samples were collected by sieving leaf litter, topsoil and by hand picking within the forest floor or vegetation. A total of 1442 individual molluscs belonging to 46 species in 11 molluscan families were collected. In number and diversity, the Streptaxidae was the most dominant family constituting 33% of the total number of species collected and 35% of the total number of individuals. Few species were abundant as most species were rare. The diversity of land molluscs in Okomu National Park is much lower than that reported for Cameroon and Sabah. Possible causes may be due to poor knowledge of the molluscan fauna and inability to sample the entire available habitat in the rainforest. Further studies in other parts of the rainforest in West Africa will provide more information on the molluscan diversity.