The herpetofauna of Hidalgo, Mexico: Composition, distribution, and conservation status

The herpetofauna of Hidalgo, Mexico, is comprised of 203 species, including 42 anurans, 17 caudates, one crocodylian, 137 squamates, and six turtles. Here, the distribution of the herpetofaunal species are catalogued among the four recognized physiographic regions. The total number of species varies from 77 in the Mexican Plateau to 166 in the Sierra Madre Oriental. The individual species occupy from one to four regions (mean = 2.1). About 69% of the Hidalgo herpetofauna is found in only one or two of the four regions, which is of considerable conservation significance. The greatest number of single-region species occupies the Sierra Madre Oriental (25), followed by the Gulf Coastal Lowlands (15), the Trans-Mexican Volcanic Belt (6), and the Mexican Plateau (2). The Coefficient of Biogeographic Resemblance (CBR) indicates that the Sierra Madre Oriental and the Gulf Coastal lowlands share the most species (72), because of their adjacent geographic position and they contain a significant number of generalist species that occur in the Gulf lowlands of Mexico, southern USA, Central America, and/or South America. The two largest geographic regions in Hidalgo by area, Sierra Madre Oriental and Mexican Plateau, reflect opposite patterns in species richness (166 and 77 species, respectively) due to overall differences in the ecological characteristics between them. A similarity dendrogram based on the Unweighted Pair Group Method with Arithmetic Averages (UPGMA) depicts two distinct clusters, one between the Sierra Madre Oriental and Gulf Coastal Lowlands and the other between the Mexican Plateau and Trans-Mexican Volcanic Belt. The former cluster reflects the two regions sharing a substantial number of herpetofaunal species that occur on the Gulf lowlands of North America and Central America, as well as a few that enter South America. The second cluster is due to the two montane regions being adjacent to one another and their ecological similarities. With respect to the distributional categories, the largest number of species is that of the country endemics (104 of 203), followed by non-endemics (92), state endemics (four), and non-natives (three). The principal environmental threats to the Hidalgo herpetofauna are deforestation, livestock, roads, pollution of water sources, cultural factors, and diseases. The conservation status of each native species was assessed by means of the SEMARNAT (NOM-059), IUCN, and EVS systems, of which the EVS system was the most useful. The Relative Herpetofaunal Priority (RHP) method was also used to designate the rank order significance of the physiographic regions and the highest values were found for the Sierra Madre Oriental. Most of the five protected areas in Hidalgo are located in the Trans-Mexican Volcanic Belt, which is only the second most important region from a conservation perspective. In addition, only 78 of the 200 native species found in Hidalgo are recorded in total from the five protected areas. Finally, a set of conclusions and recommendations are offered for the future protection of the Hidalgo herpetofauna