Ecology of Sceloporus gadsdeni (Squamata: Phrynosomatidae) from the central Chihuahuan Desert, Mexico

Populations of Sceloporus cyanostictus Axtell and Axtell, 1971 from southwestern Coahuila have been described as a new species, Sceloporus gadsdeni Castaneda-Gaytan and Diaz-Cardenas, 2017. Sceloporus cyanostictus is listed as Endangered by the IUCN Red List due to the decline in its habitat and its limited distribution. The subdivision of S. cyanostictus into two species further reduces the range and population size of each taxon, thereby posing a possible threat to the conservation status of each species. We describe here the sexual dimorphism, growth, age, population structure, sex ratio, density, and thermal ecology of S. gadsdeni to supplement the available information for one these two species. Males are larger than females, and when both sexes reach maturity after 1.1 yr, they have snout-vent lengths of about 60 mm. Population structures in the spring and summer are similar, and differ from those in the fall. The sex ratio is male-biased and varies seasonally. Population density varies from 29 to 124 individuals/ha. Mean body temperature is 32.1 degrees C and mean preferred body temperature is 32.7 degrees C. Sceloporus gadsdeni is a thermoregulator that has high thermal accuracy (d(b) = 0.02) and optimal thermal efficiency (E = 0.98) in an environment with suboptimal thermal quality during September. The data suggest that S. gadsdeni is a sexually dimorphic species that has early sexual maturity, relatively slow growth, variable population density, and effective thermoregulation.