Seasonal Thermal Ecology and Locomotor Performance of an Andean Viviparous Lizard: Assessment of Its Vulnerability to Climate Change.

Lizards, in general, tend to maintain body temperatures close to and often below physiological optima because of variations in body temperatures, as well as the asymmetry of thermal performance curves. Thermal ecophysiology has been studied in several species of the genus Phymaturus; however, Phymaturus cf. palluma is a taxon that has not yet been formally described. We evaluated key thermal ecophysiological traits of this taxon during two seasons, summer and autumn, in a high-altitude desert in the Precordillera of central-western Argentina. Seasonally, we compare thermal parameters, while during the summer, we evaluate locomotor performance traits and estimate vulnerability to global warming. In the field, we recorded body, microenvironmental, and operative temperatures. In the laboratory, we measured preferred temperatures, calculated the thermoregulatory efficiency index, and estimated the thermal sensitivity of locomotion (short and long runs) at five different body temperatures to assess its vulnerability to global warming. Significant seasonal differences were observed in preferred and body temperature in the field, but not in microenvironmental temperatures, while the preferred temperature was higher than the body temperature in both seasons, and the thermoregulatory efficiency was moderate (E = 0.68). The optimum temperature was lower than the preferred temperature, indicating a lack of support for the thermal coadaptation hypothesis. We conclude that this taxon is a eurythermic lizard and a moderate thermoregulator, with thermal sensitivity in its locomotor performance. Vulnerability indices to global warming suggest that P. cf. palluma has the ecophysiological capacity to adapt to changes in its natural environment.