Thermal biology of the southernmost lizards in the world: Liolaemus sarmientoi and Liolaemus magellanicus from Patagonia, Argentina

We determined the efficiency of thermoregulation by the southernmost liolaemids Liolaemus sarmientoi and L. magellanicus from Patagonia, Argentina (51°S), by measuring body ( T b ), microenvironmental, and operative temperatures in the field, and preferred body temperatures in the laboratory ( T pref ). L. sarmientoi was found to be a poor thermoregulator, whereas L. magellanicus was deemed to be a constrained thermoconformer. Among all known species of Liolaemus , L. sarmientoi and L. magellanicus had the lowest T b' s when tested in the field; however, their T pref' s were similar to other liolaemids. These data suggest that these southernmost liolaemid species have not evolved appropriate thermoregulatory behaviors or made adequate physiological adaptations to face the extreme thermal challenges of their environment.