Herpetofauna of two biogeographic transects in eastern Mexico

Abstract

The north-south frontal ridge of the Sierra Madre Oriental is twice divided by eastwardly flowing rivers, the Rio Moctezuma and the Rio Santa Maria. Between these rivers, an isolated portion of that ridge comprised much of the Xilitla-Eastern Queretaro area. Two isolated pine-oak forests separated by an intervening arid valley, comprised the habitat for ninety-eight known species of amphibians and reptiles. Study of this area was made possible by the presence of two road transects. One transect, extended in a northeast to southwest direction and traversed three physiographical regions and five major vegetational zones. The second transect, extended in a north-south direction and traversed the length of an isolated dry central valley. Altitudes within the Xilitla-Eastern Queretaro area were found to range between 100 and 2400 meters. Geologically. The area contained limestone ridges arising from ancient coral beds and numerous caverns and karst skins were located throughout the area. The climate was seasonal, consisting of summer rains followed by dry winters. Pleistocene climatic changes coupled with post-Columbian agricultural practices appear to have played a major role in influencing the current herpetofaunal distribution.