Thermal biology of the endemic lizard <i>Phymaturus verdugo</i>: is it as conservative as we think?

Abstract Under the scenario of global climate change, understanding how animals cope with environmental changes might help to predict their future responses. The genus Phymaturus serves as a valuable model for studying thermal biology owing to its conservatism in thermal traits, despite its broad latitudinal distribution. By examining two geographically close populations of the lizard Phymaturus verdugo from the Andean mountains, we aimed to determine whether body mass, dorsal melanism, and microclimatic conditions influence their thermal biology. The species demonstrates moderate to good thermoregulation, with females increasing effectiveness in sites with lower thermal quality. Although their preferred temperature remained consistent across populations, significant differences in body temperature, effectiveness of thermoregulation, and heating times were observed. Melanism, proposed to enhance heating in cold environments, showed limited effects on thermoregulation, accelerating heating times only in specific conditions (males heating from 15°C to 35°C at the colder site). Instead, body mass emerged as the key factor that consistently slowed heating times. Our findings suggest that P. verdugo relies heavily on behavioural strategies for thermoregulation, allowing individuals to cope with immediate thermal variability, but the ability to adapt to future climate change remains uncertain, because these responses might provide short-term benefits but limit long-term physiological adaptation.