HIGH DIVERSITY AND REGIONAL ENDEMISM IN LAND SNAILS OF EASTERN TANZANIA

In February/March 1995 we collected land snails (including slugs) at 1 2 stations in eastern Tanzania. A total of 571 person-hours yielded 91 74 snails assigned to 159 morpho-species. The richest two sites each ( < 4 ha of uniform forest) had 50 species (Amboni Cave) and 48 species (near Amani, Usambaras), nearly as great as the most species-rich site s known in the world; sieving of litter and soil would probably yield more species. In lowland (coastal) forests, both diversity and endemis m seemed to decrease from north to south. Most snail species were foun d within only one of four coastal or one montane geographic regions, i ndicating substantial regional endemism. Only one species (Achatina fu lica) appeared in all five regions, and 84 % of all other species were found in only one (61 %) or two regions (23 %). The predatory strepta xids comprised about half the species and a third of the individuals a t the Usambara site, an extremely high ratio of carnivores. Small snai ls (< 5 mm greatest adult shell dimension) - many of which are probabl y undescribed species - comprise a substantial proportion of Tanzanian molluscan diversity; more surveys are needed, especially because of h uman pressures on the few forest patches remaining.