Hot Lizards: Testing the Tolerance to Climate Warming of Thermoconformers in the Andes (Squamata: Gymnophthalmidae)

Abstract

Climate change is one of the greatest threats to species across the globe, but the threats to tropical animals have largely been overlooked. Tropical high elevation species are distinctly at risk as they will be unable to disperse to habitats with favorable temperatures in the future. Twenty percent of all lizard species may be faced with extinction. Proctoporus unsaacae and P. sucullucu are two thermoconforming lizard species native to the Central Andes mountains where their habitats are predicted to rise over 3°C within the 21st century. Because these species do not thermoregulate behaviorally, we predicted that they would have narrow temperature tolerances and would be vulnerable to climate warming. We collected lizards of these species in Peru and tested their critical thermal maxima (CTmax) by slowly heating them until they were unable to maintain normal bodily functions, measured by muscular spasms. Surprisingly, we found that the species have high thermal tolerance with P. unsaacae averaging 38.2°C CTmax and P. sucullucu averaging 39.4°C. The difference between CTmax and field active body temperatures for both species exceeded 20°C. Based on our results, increased environmental temperature will not directly cause these species to suffer death or activity restriction. We posit that these species of Proctoporus and the few other truly eurythermic lizard species may be particularly well suited to surviving global temperature increases. Although global warming will continue to cause the decline and extinction of species worldwide, more research is needed on species with unusual ecologies before making sweeping statements about the dire fate of reptiles.