FOREST AND SCRUB SNAIL FAUNAS FROM NORTHERN MADEIRA

The island of Madeira has two major natural vegetation types, a damp f orest association at higher altitudes, with below it a dry association of grasses, herbs and low scrub. The open scrub is predominantly on t he south coast and the eastern peninsula. The land mollusc fauna of th e high forest and the north coast has been surveyed, and compared with that of other regions. Presence or absence of 84 species, 56 of them endemic, has been recorded in 51 samples. The forest samples are very clearly separated from those of the other regions; species in the fami lies Pupillidae and Vitrinidae have radiated there, whereas radiation of Helicidae is characteristic of the other areas. Where non-endemics are present, they increase the species richness and do not displace en demics. There is no evidence of subdivisions within the forest fauna. Previous work has shown that at lower and drier locations an eastern p eninsula fauna is differentiated from that of the south coast. The exi stence of the forest accounts for some of the species richness of the Madeiran archipelago, but much of it is attributable to species prolif eration, especially in the Helicidae, between similar scrub habitats o n different islands and on different parts of the same island.