Acclimatisation to tropical seasons: hydric and thermal physiology in Gehyra geckos.

Seasonal acclimatisation is a mechanism enabling individuals to advantageously adjust one or more physiological parameters in response to changing environmental conditions. 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 few studies have examined the ability of reptiles to exhibit seasonal flexibility in rates of evaporative water loss (EWL). We measured acclimatisation to seasonal changes for both temperature and water-related traits 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 (Tpref), but Tpref was significantly lower during the cooler dry season in three species from a semi-arid, more thermally variable site. EWL was lower (34-76% reduction) during the dry season compared with the wet season, representing a significant reduction for all gecko species. EWL decreased rapidly from wet to early dry season, then either remained low or continued to decrease to a minimum in the late dry season. These results indicate acclimatisation in EWL, resulting in the conservation of water during the dry season. A growing body of evidence suggests that seasonal acclimatisation of EWL broadly occurs in lizards in the wet-dry tropics of Australia, but less is known about seasonal acclimatisation of EWL in other geographic regions.