Neotropical mammals and the myth of amazonian biodiversity.

Data were compiled on the distribution of mammal taxa (883 species, 242 genera, 45 families, and 10 orders) among South America's six major macrohabitats: lowland Amazon forest, western montane forests, Atlantic rain forest, upland semideciduous forest, southern mesophytic forest, and drylands. The drylands are the richest area in numbers of species supported and are more diverse than the other habitats, including the lowland Amazon rain forest, when endemics are considered. An analysis of number of endemic and nonendemic taxa versus size of area found a simple positive linear relationship: the drylands, almost twice as extensive as the Amazon lowlands, support more endemic taxa. Conservation plans that emphasize the wet tropics and fail to consider the drylands as special repositories of mammal diversity will be unable to preserve a significant number of novel taxa.