NESTEDNESS, BIOGEOGRAPHIC THEORY, AND THE DESIGN OF NATURE-RESERVES

I examine the relationship between nested distributional patterns and the degree to which several small reserves will contain more species t han would a single reserve of equal total area (SLOSS). Nestedness is a common property of species distributions on real and habitat islands . However, there is considerable variation in nestedness among species distributions, some of which is related to the physical and biologica l background of the archipelagoes. Nestedness does not vary according to the taxonomic group examined (with the exception of aquatic inverte brates). Nestedness does vary between real and habitat islands (with a quatic invertebrates excluded), but not between oceanic and land-bridg e islands. The more a biota is nested, the more likely it is that a si ngle large reserve would preserve more species. However, nestedness is a rather poor predictor of SLOSS, as the vast majority of archipelago es support a strategy of several small reserves, even though almost al l of them are significantly nested. Nestedness says little about optim al reserve design and management, and appears to be a weak conservatio n tool.