The biogeography of warming tolerance in lizards

Aim Many ectotherms are at risk from climate change as temperatures are increasingly exceeding their thermal limits. Many evaluations of the vulnerability of ectotherms to climate change have relied on statistical metrics derived from coarse-scale climatic data, which may result in misleading predictions. By applying an integrative approach, we investigated geographical correlates of the vulnerability of lizards to climate change. Location Globally. Taxon Lizards. Methods We combined data on lizard thermal physiology and ecology, with high-resolution climate data and biophysical modelling to assess lizards' vulnerability to climate change. We calculated warming tolerance (difference between their body temperatures and upper thermal limits) and number of hours of activity. We investigated associations between warming tolerance and activity time with latitude, altitude and biome types. We compared our approach with traditional methods to calculate warming tolerance (using solely macroclimatic data). Results We found no latitudinal trend in the warming tolerance of lizards calculated from body temperature, but there was a weak negative correlation with altitude. We found associations between hours of activity and latitude and altitude. Desert species showed narrower warming tolerance than tropical and temperate species. Desert species and temperate species had reduced hours of activity when compared to tropical species. When warming tolerance was calculated from macroclimatic data, however, it was positively correlated with latitude and altitude, and species from tropical forested biomes showed narrow warming tolerances. Main Conclusions Vulnerability metrics calculated from macroclimatic data can produce divergent outcomes to those observed from fine-scale climatic data. Our work indicates that the ability of desert and temperate lizard species to cope with heat stress by thermoregulating is more constrained than that of tropical species. Integrative assessments of ectotherms' vulnerability to climate change can highlight species and regions that should be prioritised for conservation management.