Abstract

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.