Thermal ecology of a thermophilic lizard Callisaurus draconoides through a latitudinal gradient.

Abstract

Desert squamates need to regulate their body temperature within a specific range in response to extreme temperatures. Variation of thermal resources through altitudinal and latitudinal gradients influences the thermal physiological traits and thermoregulation of organisms. In some species, the physiological requirements between populations can vary correlated with environmental conditions. In other species, the physiological parameters may remain similar across geographic gradients. In this study, we compared the thermal requirements and thermoregulatory strategies of a lizard (Callisaurus draconoides) that inhabits contrasting desert ecoregions across a latitudinal gradient. To assess thermoregulation of C. draconoides, we measured their field body temperature during periods of activity, the preferred body temperature in a laboratory thermal gradient and the environmental operative temperature in three contrasting sites. We also analyzed and compared three thermoregulatory indices (accuracy and effectiveness of thermoregulation and habitat thermal quality) for each population. Our results suggest that C. draconoides maintains similar thermal requirements and tolerances across its distribution range. Furthermore, their thermoregulation was accurate and effective in low thermal quality environments. Therefore, the thermoregulation in C. draconoides is essential to buffer extreme environmental conditions and avoid the deadly consequences of overheating in each ecoregion along the Baja California peninsula.