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Aim: Squamate fitness is affected by body temperature, which in turn is influenced by environmental temperatures and, in many species, by exposure to solar radiation. The biophysical drivers of body temperature have been widely studied, but we lack an integrative synthesis of actual body temperatures experienced in the field, and their relationships to environmental temperatures, across phylogeny, behaviour and climate. Location: Global (25 countries on six continents). Taxa: Squamates (210 species, representing 25 families). Methods: We measured the body temperatures of 20,231 individuals of squamates in the field while they were active. We examined how body temperatures vary with substrate and air temperatures across taxa, climates and behaviours (basking and diel activity). Results: Heliothermic lizards had the highest body temperatures. Their body temperatures were the most weakly correlated with substrate and air temperatures. Body temperatures of non‐heliothermic diurnal lizards were similar to heliotherms in relation to air temperature, but similar to nocturnal species in relation to substrate temperatures. The correlation of body temperature with air and substrate temperatures was stronger in diurnal snakes and non‐heliothermic lizards than in heliotherms. Body‐substrate and body‐air temperature correlations varied with mean annual temperatures in all diurnal squamates, especially in heliotherms. Thermal relations vary with behaviour (heliothermy, nocturnality) in cold climates but converge towards the same relation in warm climates. Non‐heliotherms and nocturnal species body temperatures are better explained by substrate temperature than by air temperature. Body temperature distributions become left‐skewed in warmer‐bodied species, especially in colder climates. Main Conclusions: Squamate body temperatures, their frequency distributions and their relation to environmental temperature, are globally influenced by behavioural and climatic factors. For all temperatures and climates, heliothermic species' body temperatures are consistently higher and more stable than in other species, but in regions with warmer climate these differences become less pronounced. A comparable variation was found in non‐heliotherms, but in not nocturnal species whose body temperatures were similar to air and substrate irrespective of the macroclimatic context. [ABSTRACT FROM AUTHOR]

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 38C 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 38.28C CTmax and P. sucullucu averaging 39.48C. The difference between CTmax and field active body temperatures for both species exceeded 208C. 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. [ABSTRACT FROM AUTHOR]

Aim Temperature influences most components of animal ecology and life history - but what kind of temperature? Physiologists usually examine the influence of body temperatures, while biogeographers and macroecologists tend to focus on environmental temperatures. We aim to examine the relationship between these two measures, to determine the factors that affect lizard body temperatures and to test the effect of both temperature measures on lizard life history. Location World-wide. Methods We used a large (861 species) global dataset of lizard body temperatures, and the mean annual temperatures across their geographic ranges to examine the relationships between body and mean annual temperatures. We then examined factors influencing body temperatures, and tested for the influence of both on ecological and life-history traits while accounting for the influence of shared ancestry. Results Body temperatures and mean annual temperatures are uncorrelated. However, accounting for activity time (nocturnal species have low body temperatures), use of space (fossorial and semi-aquatic species are 'colder'), insularity (mainland species are 'hotter') and phylogeny, the two temperatures are positively correlated. High body temperatures are only associated with larger hatchlings and increased rates of biomass production. Annual temperatures are positively correlated with clutch frequency and annual longevity, and negatively correlated with clutch size, age at first reproduction and longevity. Main conclusions Lizards with low body temperatures do not seem to have 'slower' life-history attributes than species with high body temperatures. The longer seasons prevalent in warm regions, and physiological processes that operate while lizards are inactive (but warm enough), make environmental temperatures better predictors of lizard life-history variation than body temperatures. This surprisingly greater effect of environmental temperatures on lizard life histories hints that global warming may have a profound influence on lizard ecology and evolution. [ABSTRACT FROM AUTHOR]