DISTRIBUTIONS OF BATS ALONG AN ELEVATIONAL GRADIENT IN THE ANDES OF SOUTH-EASTERN PERU

At least 193 species of mammals are known to occur within the Manu Bio sphere Reserve in south-eastern Peru, contributing to its stature as o ne of the world's richest protected areas. Bats (Order Chiroptera) com prise more than 42% (82 species) of this diversity. Analyses of bat ca pture records over a transect extending more than 3 km in elevation sh ow that most bat species at Manu are widely distributed in the Amazon Basin. Few are montane endemics or are localized in south-eastern Peru , although exceptions to this generalization include two species new t o Science. Highland bat faunas tend to be attenuated versions of those found below, and the elevational zonation of bat communities is weak. Species turnover with elevation Is monotonic and more-or-less smooth, with Jaccard's similarity values falling to 0.5 for sites differing b y 750 m in elevation. Subtle and orderly change in species composition with elevation is also reflected in the nested-subset structure of th ese communities; over 19 different levels, this pattern Of hierarchica l structure is both striking and highly significant. Elevational range s of species generally increase with elevation, in accordance with Ste vens' extension of 'Rapoport's rule' of range amplitude. However, Supp ort for 'Stevens' rule' may be trivial, given Amazonian richness and A ndean impoverishment. Reduced richness and poorly developed endemism i n Andean bat communities contrast with patterns shown by Sympatric rod ent faunas, which are diverse and Strongly endemic on the Altiplano an d markedly zoned along the Eastern Versant. Contrasts are less sharp w ith bird communities, which nevertheless exhibit stronger zonation and higher endemicity. Factors responsible for these distinctive distribu tional patterns are discussed.