Interplay between thermal and hydric traits in psammophilous <i>Liolaemus</i> lizards of the arid Monte Desert, Argentina

Sympatric ectotherms belonging to the same guild often exhibit differences in thermal ecophysiology as a result of their evolutionary history or current ecological interactions. This study investigated the thermal biology and hydroregulation of two sympatric lizard species, Liolaemus riojanus and L. cuyanus, in the challenging environment of the arid Monte Desert of Argentina. We examined field body temperatures (Tb), preferred temperatures (Tpref), thermoregulatory efficiency, critical thermal limits (CTmin, CTmax), panting temperature (Tpant) and total evaporative water loss (TEWL) under representative experimental temperatures. Despite similar field Tb and moderate thermoregulatory efficiency, significant interspecific differences emerged in laboratory traits. Liolaemus riojanus, the smaller species, exhibited a higher Tpref, a broader thermal tolerance (lower CTmin, higher CTmax), higher Tpant and lower TEWL compared with L. cuyanus. Furthermore, L. riojanus showed reduced EWL at high experimental temperatures (40°C), suggesting that species with higher thermal tolerance conserve water under warm conditions despite the higher surface area to volume ratio. Conversely, L. cuyanus displayed increased EWL with rising experimental temperatures, which is likely related to its relatively low CTmax and panting temperature, promoting water loss. These divergent physiological strategies likely contribute to thermal segregation in this harsh environment. Given the current trend towards aridification and climate warming, understanding the interplay between thermal and hydric traits is crucial for predicting the persistence of these lizards under changing environmental conditions and to guide management measures.