Implications of climate change on the habitat shifts of tropical lizards

The effect of temperature on the distributions of ectothermic vertebrates is well documented. Despite the increase of 6 degrees C expected in the next 60 years in South America, numerous vertebrates are still considered as 'Least Concern' species by the IUCN due to their large distribution, insufficient widespread threats and insignificant population decline. One example is the lizard Tropidurus torquatus (Squamata: Tropiduridae), commonly found thermoregulating in anthropic environments throughout the Brazilian Cerrado, but restricted to gallery forests in the equator-ward localities. The urban areas in this warmer region have been colonised by other closely related congeners (e.g. Tropidurus oreadicus). This study aimed to understand this divergence of habitat selection by these tropirudids that may explain some of the species responses to past and future climate warming. We collected body temperatures (T-b), micro-environmental temperatures (T-a) and operative (T-e) temperatures in four sites along a latitudinal gradient: a pole-ward and two central sites where T. torquatus inhabit urban areas and one equator-ward site where T. torquatus and T. oreadicus occur in the gallery forest and in urban microhabitats, respectively. All three populations of T. torquatus present similar T-b (35.5-36 degrees C) and shared microhabitats with a similar T-a (34-37.3 degrees C). The T-e in the equator-ward urban site was considerably higher than in the gallery forest. Tropidurus oreadicus T-b was 38.2 degrees C (30.1-41.3 degrees C) and was active at a T-a of 30.5-42.3 degrees C. The overlap between the genus T-b, T-a and T-e highlights a decrease in the hours of activity that lizards would experience under climate warming. The reduction of hours of activity together with the devastation of natural habitats represents threats and an alarming scenario especially for the equator-ward populations.