Number of Amphibian Species by Freshwater Ecoregion

Number of amphibian species, by freshwater ecoregion.

We calculated the number of amphibian species per freshwater ecoregion using species range maps of the Global Amphibian Assessment (GAA, www.iucnredlist.org/amphibians) (IUCN et al. 2006). The 2006 GAA assessed 5,918 amphibian species and provided distribution maps for 5,640 of those species. When a range overlapped several ecoregions, we counted species as present in all those ecoregions that had part of the range. This may have resulted in an overestimate of species numbers in some ecoregions, especially those that are long and narrow in shape. This is particularly true for the Amazonas High Andes ecoregion (312), where the mountain range has been used as a range boundary for hundreds of species. Distribution maps from the GAA represent the “extent of occurrence” for each species—that is, the area contained within the shortest continuous imaginary boundary, which can be drawn to encompass all the known, inferred, or projected sites of present occurrence of a taxon. Because of the conservative approach taken in the GAA to mapping species, the ranges for many species are likely to be minimum estimates. The GAA followed a rule of allowing interpolation of occurrence between known locations if the ecological conditions seem appropriate, but not permitting extrapolation beyond known locations. Some species are therefore almost certain to occur much more widely than the GAA has mapped. Because of this, some regions were recorded as having much lower numbers. Finally, the percentage of data-deficient species (23.4 percent) were very high compared to other taxa in the GAA.

These data were derived by The Nature Conservancy, and were displayed in a map published in The Atlas of Global Conservation (Hoekstra et al., University of California Press, 2010). More information at http://nature.org/atlas.

Data derived from:
International Union for Conservation of Nature (IUCN), Conservation International, and NatureServe. 2006. Global Amphibian Assessment. www.iucnredlist.org/amphibians. Digital media.