Biogeographic distribution patterns of south american amphibians: A regionalization based on cluster analysis

Abstract

We devise a regionalization system based on the geographical distribution of 2,265 amphibian species in South America. We used range maps of amphibians to obtain a presence/absence data grid resolved to 9310 km2. Biogeographical regions were generated by submitting the dataset to k-means clustering combined with v-fold cross-validation. The boundaries of the three clusters generated by multiple runs of the analysis are congruent with broadly defined biome structure in South America: 1) the Andes, the Atacama desert, Patagonia, and subtropics including grassland in southern Brazil, Argentina and Uruguay; 2) Amazon forest; 3) Atlantic forest and the Cerrado-Caatinga-Chaco complex. A few runs further distinguished Atlantic forest and Caatinga biome from other drier, more open biomes. The variable most strongly associated with the distribution of clusters was species richness, but climate also had moderately strong explanatory power. The regionalization scheme based on clustering is less finely resolved than previous schemes generated by expert opinion and rates of endemism but provides a general overview of the biogeographic signal contained in the current distribution patterns of amphibian species. © 2011 ABECO.