Thermal sensitivity of performance of Phymaturus palluma (Liolaemidae) in the highlands of Aconcagua: vulnerability to global warming in the Andes

Abstract

Ectotherms are especially vulnerable to climate change due to their dependence on environmental thermal conditions to obtain adequate body temperatures for physiological performance. An approach to predict the impact of global warming in ectotherms is quantifying their locomotor sensitivities to temperature across the thermal performance curves (TPCs) owing to the crucial role running plays on most of their activities, like dispersion, reproduction, and foraging. Here, we have examined the relationship between body temperature (Tb) and locomotor performance in juveniles and adults of the high-mountain lizard Phymaturus palluma. We have determined the speed in long (LR) and sprint runs (SR) at five different body temperatures, and their relationship with morphological traits. In addition, we have measured the operative temperatures in the microenvironments used by P. palluma to evaluate their vulnerability to global warming. For this, we have estimated the thermal safety margin and warming tolerance. Phymaturus palluma showed a left-skewed TPCs for LR and SR. The optimal temperature (To) matched the set point of preferred temperatures and the performance breadth was correlated with the variance in Tb registered in the field, as the thermal coadaptation hypothesis predicts. The rising temperatures projected by the study site could represent a threat for the species, because currently P. palluma experiences operative temperatures that include their performance breadth and To. Moreover, we have demonstrated that the species currently exhibit negative thermal safety margins, thus an increase in ambient temperatures will reduce the amount of time in which lizards could achieve an optimal performance.