Climatic Variability Shapes Plasticity of Hydric and Thermal Physiology in Tropical Geckos

Phenotypic plasticity in reptiles is a key mechanism enabling individuals to maintain and optimize physiological responses to changing environments. The ability to adjust metabolic rates and thermal physiology in response to seasonal changes is known to be central to the physiological ecology of some reptiles, but less is known about reptiles’ ability to exhibit seasonal flexibility in rates of evaporative water loss (EWL). Physiological acclimatization to seasonal changes was measured in six species of geckos in the genus Gehyra from the highly seasonal tropics of northern Australia. Four species from a mesic, more thermally stable site did not have seasonal differences in thermal preference (Tp), but Tp was significantly lower during the cooler dry season in three species from a semi-arid, more thermally variable site. EWL was significantly lower (42% to 78%) during the dry season compared to the wet season for all species. For most species, EWL decreased rapidly from wet to early dry season, then continued to a minimum in the late dry season. There was no relationship between extent of plasticity and geographic range size. These results demonstrate high plasticity and imply a cost to maintaining low EWL, the basis of which requires further study.