Are lizards feeling the heat? A tale of ecology and evolution under two temperatures

<p>Aim Temperature influences most components of animal ecology and life history– but what kind of temperature? Physiologists usually examine the influence ofbody temperatures, while biogeographers and macroecologists tend to focus onenvironmental temperatures. We aim to examine the relationship between thesetwo measures, to determine the factors that affect lizard body temperatures and totest 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 examinethe relationships between body and mean annual temperatures.We then examinedfactors influencing body temperatures, and tested for the influence of both onecological and life-history traits while accounting for the influence of sharedancestry.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 positivelycorrelated. High body temperatures are only associated with larger hatchlings andincreased rates of biomass production. Annual temperatures are positively correlatedwith clutch frequency and annual longevity, and negatively correlated withclutch 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 longerseasons prevalent in warm regions, and physiological processes that operate whilelizards are inactive (but warm enough), make environmental temperatures betterpredictors of lizard life-history variation than body temperatures. This surprisinglygreater effect of environmental temperatures on lizard life histories hints that globalwarming may have a profound influence on lizard ecology and evolution.</p>