Meeting Abstract
Species with broad geographic distributions often have populations inhabiting disparate habitat types that vary in thermal quality. Recent models suggest that differences in the thermal environment should lead to divergence in the thermal ecology of populations. Yet, evidence to date suggests thermal rigidity in key thermal traits, such as preferred temperature and field active body temperatures. Because one potential response to climate change is phenotypic plasticity, evaluating the potential for local adaptation to environmental gradients may enhance our understanding of how species may cope with altered thermal niches. Here we estimate the variation in thermal and physiological traits among populations of the lizard species, Urosaurus ornatus along an 1100 m elevational gradient in Arizona. We measured preferred temperature, critical thermal minima and maxima- the lower and upper thresholds for physiological function-, field active body temperature, and the thermal sensitivity of locomotor performance for low (750m), mid (1300m), and high (1850m) elevation populations of U. ornatus. Individuals at lower elevations had higher critical thermal maxima, whereas at high elevations they exhibited lower critical thermal minima. Preferred body temperatures declined with increasing elevation. The field active body temperatures of U. ornatus from low elevations were higher than those at higher elevations. The differences in thermal biology suggest that populations of U. ornatus along this gradient are locally adapted to specific thermal niches. The lack of thermal rigidity in these traits indicates that differences in thermal quality of habitats can lead to physiological changes within lizards. Physiological consequences due to thermal habitat selection may thus be severe as thermal niches change due to climate warming.
