Species richness and distribution of Neotropical rodents, with conservation implications

The correlates of species richness and conservation status of South American rodents were studied by analyzing the ranges of 791 species (belonging to 159 genera and 16 families). The distribution data (size of each species' range in km(2)) and the relative quantity of each macrohabitat type (in km(2)) were obtained from the Global Mammal Assessment data bank of the International Union for Conservation of Nature (IUCN), and the Global Land Cover 2000, respectively. We excluded mainly island species from analyses but included those species that occur on both islands and the mainland. Habitats were grouped according to seven categories (shrubland, forest, grassland, savannah, wetlands, desert, and artificial). Mean range sizes varied significantly among families, with members of the family Cuniculidae having larger ranges than the species belonging to the rest of the families. Mean range size did not differ significantly between endemic and non-endemic taxa. There was a significant positive relation between total species richness and the availability of habitat types. Specialized species (i.e., those linked to a single habitat type) were found especially in forests, but shrublands and grasslands were also important. IUCN threatened species were distributed in a scattered way, and essentially in forests, grasslands, and shrublands. No region of the Neotropics housed more than two to three threatened taxa, apart from a spot in north-central Peru with five species. The richness of IUCN threatened species was higher in the montane forest ecosystems of the Andes, north-central Peru, than in other areas of South America. There was a mismatch between the hotspot maps for threatened and endemic species. The conservation implications of these patterns are discussed.