DIVERSITY OF SMALL MAMMALS IN THE PACIFIC COASTAL DESERT OF PERU AND CHILE AND IN THE ADJACENT ANDEAN AREA - BIOGEOGRAPHY AND COMMUNITY STRUCTURE

Species diversity patterns of small mammals (sigmodontine rodents) in the Chilean-Peruvian Pacific coastal desert and adjacent Andean area ( Puna) were analysed by means of latitudinal and altitudinal transects. The statistical analyses of the patterns show: (1) a wide variation i n latitudinal species diversity, with a peak in the region where the P una reaches its greatest areal extent; (2) the differentiation of at l east four groups of distinct faunal elements resulting from the intera ction of large-scale biogeographic, geological and evolutionary proces ses; (3) a positive correlation between species richness and altitude for the altitudinal transects located within the Pacific coastal deser t area and Puna; and (4) a highly individualistic pattern of community structure at a regional scale. These results are discussed considerin g biogeographic, palaeoclimatic and evolutionary processes, such as th e establishment of the Pacific coastal desert, and the existence of a major centre of species diversification in the Puna area. Similarities and differences between these community-level patterns and those in N orth American deserts are discussed.