Thermal-metabolic phenotypes of the lizard Podarcis muralis differ across elevation, but converge in high elevation hypoxia

In response to a warming climate, many montane species are shifting upslope to track the emergence of preferred temperatures. Characterizing patterns of variation in metabolic, physiological and thermal traits along an elevational gradient, and the plastic potential of these traits, is necessary to understand current and future responses to abiotic constraints at high elevations, including limited oxygen availability. We performed a transplant experiment with the upslope-colonizing common wall lizard (Podarcis muralis) in which we measured nine aspects of thermal physiology and aerobic capacity in lizards from replicate low- (400 m above sea level, ASL) and high-elevation (1700 m ASL) populations. We first measured traits at their elevation of origin and then transplanted half of each group to extreme high elevation (2900 m ASL; above the current elevational range limit of this species), where oxygen availability is reduced by ∼25% relative to sea level. After 3 weeks of acclimation, we...