DIVERSITY AND DURABILITY - RESPONSES OF THE MADEIRAN AND PORTO-SANTANSNAIL FAUNAS TO NATURAL AND HUMAN-INDUCED ENVIRONMENTAL-CHANGE

The snail fauna of the Madeiran Archipelago has the high regional dive rsity and endemism, and high species and genus differentiation between islands characteristic of oceanic island faunas. It is unusual in two respects: the existence of good Pleistocene/Holocene fossil records, and the apparent durability of the endemic fauna in the face of massiv e human disturbance and the introduction of non-indigenous species. We use the fossil record, the present microdistributions of species, and the environmental records available to track the generation of divers ity and the response to human disturbance. The nature of the environme nt available and the life-habits of endemic species appear to account for the relative resilience of these species.