The herpetofauna of Tabasco, Mexico: composition, distribution, and conservation status

The herpetofauna of Tabasco, Mexico, consists of 170 species, including 39 anurans, five caudates, one caecilian, two crocodylians, 111 squamates, and 12 turtles. We catalogued the distribution of these species among the three physiographic regions we recognize in the state: the Gulf Coastal Plain (88 species), the Sierras Bajas de Peten (93 species), and the Sierra Norte de Chiapas (145 species). The individual species are found in either one, two, or all three regions (mean = 1.9). Approximately 68% of the herpetofauna in Tabasco occupies only one or two of the three regions, which is of important conservation significance. The largest number of single-region species is found in the Sierra Norte de Chiapas (50), followed by the Gulf Coastal Plain (12) and the Sierras Bajas de Peten (nine). Coefficient of Biogeographic Resemblance (CBR) calculations indicate that the Sierra Norte de Chiapas and the Sierras Bajas de Peten share the greatest number of species (79), followed by 71 species between the Sierra Norte de Chiapas and the Gulf Coastal Plain, and 61 between the Gulf Coastal Plain and the Sierras Bajas de Peten. Fifty-five species occupy all three regions. A similarity dendrogram based on the Unweighted Pair Group Method with Arithmetic Averages (UPGMA) illustrates that the Sierras Bajas de Peten clusters with the Gulf Coastal Plain at the 0.67 level and the Sierra Norte de Chiapas clusters with the previous pair at the 0.64 level, and overall indicates an intermediate level of similarly. With reference to distributional categories, the greatest number of species is represented by the non-endemic species (146 of 170), followed by the country endemics (20), and the non-natives (five). Of the 146 non-endemic species, the majority (95) are MXCA species (i.e., those found only in Mexico and Central America). The principal environmental threats to the Tabasco herpetofauna are deforestation, agricultural activities, roads, soil contamination and oil extraction, myths and cultural factors (gastronomy), illegal commerce, and forest fires. We evaluated the conservation status of each of the native species by using the SEMARNAT, IUCN, and EVS systems, of which the EVS system provided the most inclusive assessment of the state's herpetofauna. We also employed the Relative Herpetofaunal Priority (RHP) method to determine the rank order of the three physiographic regions and found the highest values in the Sierra Norte de Chiapas. Most of the protected areas in the state are located in the Gulf Coastal Plain, which is only the second or third most important region from a conservation perspective. Nonetheless, about 95% of the native herpetofauna has been documented within the system of protected areas. Finally, we provide a set of conclusions and recommendations for the future protection of the Tabasco herpetofauna.