Number of Freshwater Turtle and Crocodilian Species by Freshwater Ecoregion

Number of turtle and crocodilian species, by freshwater ecoregion.

We generated the map of freshwater turtle and crocodilian species richness—the number of species present in each ecoregion—from species distribution maps, primarily drawing on the sources listed below.
Distribution maps for 260 freshwater turtle species were provided by Buhlmann et al. (2007). The original distribution maps represented coarse ranges of where species were thought to be present in the wild; however, they were not exact ranges. Buhlmann et al. compiled data from museum and literature records. They correlated verified locality points with GIS-defined hydrologic unit codes (HUCs) and subsequently created “projected” distribution maps for each species by selecting additional HUCs that were representative of similar habitats, elevations, and physiographic regions as the HUCs with the verified point localities. The amount of information available varied by species, as some species and regions are better studied than others. In addition, many species names, especially in the tropics, actually represent complexes of several turtle species that have not yet been disaggregated.

In developing our map, when a range overlapped several ecoregions, we counted species as present in all those ecoregions that had part of the range. Some ecoregions with a long and narrow shape may have an overestimation of species in our map given the way the range polygons were drawn. This is particularly true in the Amazonas High Andes ecoregion (312), where the mountain range has been used as a range boundary for hundreds of species.
For crocodilians, species range maps are from the IUCN-SSC Crocodile Specialist Group and Britton (2007). Species range maps were assessed visually, and species presence was assigned to ecoregions. When a range overlapped several ecoregions, we counted the species as present in all ecoregions of range overlap.

These data were derived by The Nature Conservancy and World Wildlife Fund, 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.

The following were our primary data sources:
Britton, A. 2007. Information on crocodilian species distributions. Available at www.flmnh.ufl.edu/cnhc/csl.html.

Buhlmann, K. A., T. B. Akre, J. B. Iverson, D. Karapatakis, R. A. Mittermeier, A. Georges, G. J. Rhodin, P. P. van Dijk, and J. W. Gibbons. 2007. A global analysis of tortoise and freshwater turtle distributions. Data from the preliminary results of the Global Reptile Assessment. International Union for Conservation of Nature–Species Survival Commission (IUCN-SSC), Conservation International/Center for Applied Biological Science (CI/CABS), and Savannah River Ecology Laboratory, University of Georgia, Aiken, South Carolina, USA.

International Union for Conservation of Nature (IUCN)–SSC Crocodile Specialist Group Web site. 2008. Available at http://iucncsg.org/ph1/modules/Home/.