Low repeatability of preferred body temperature in four species of Cordylid lizards: Temporal variation and implications for adaptive significance

Preferred body temperatures (T-sel) of ectotherms are important for ecological and evolutionary studies. In lizards, the measurement of T (sel) is controversial for several reasons, generally related to hypotheses addressing how T-sel may evolve in the wild. Although seldom explicitly tested, evolutionary hypotheses of adaptation to local climate require that T-sel meets the conditions of natural selection, which include repeatability, heritability and a link to fitness. Here, we investigated repeatability (tau, intra-class correlation coefficient) of T-sel at several time-scales using four Cordylid species from heterogeneous thermal habitats. Although there was significant inter-individual variation within days (P < 0.005 in most cases), there was no significant inter-individual variation when calculated across several days (P > 0.05). Repeatability was low in all species investigated (from 0 to 0.482) when compared against other estimates of repeatability of T-sel in the literature. Irrespective of how T-sel was calculated, it showed inconsistent and variable temporal effects across species. Furthermore, repeatability of T-sel did not change with acclimation to laboratory conditions. These data have implications for understanding the evolution of thermoregulation in these and other ectotherms.