Ecological constraints to match field and preferred temperatures in lizards Tropidurus catalanensis (Squamata; Tropiduridae).

Abstract

We compared microhabitat and body temperatures in the field with thermal preferences of Tropidurus catalanensis to investigate if they match or diverge as demonstration respectively of suitability or poor-quality of the thermal environment. As T. catalanensis is subjected to variable thermal conditions along its distribution and may be jeopardized by the climate change, we measured its thermal preferences after exposure to milder (17\xa0°C-27\xa0°C) and warmer (22\xa0°C-32\xa0°C) thermal conditions to evaluate acclimatory responses and tolerances and vulnerabilities to warming. Field body temperatures tended to be similar to minimum preferred body temperatures, and microhabitat and body temperatures in the field were cooler in the remaining comparisons with thermal preferences [preferred (Tpref), set-point range (Tset), minimum preferred (Tpref_min) and maximum preferred (Tpref_max) body temperatures], suggesting there was a constraint to warming up in nature. The minimum preferred body temperatures may be a threshold separating proper functioning from markedly noxious impacts due to progressive impairment by the cooling. Difficulties to warm and keep suitable body temperatures may jeopardize overall ecophysiological and behavioral processes with implications for maintenance, fitness, and survival. The constraints to warm may impact T. catalanensis differently depending on its body size and its properties of heat conservation (thermal inertia). Smaller and larger T. catalanensis may respectively cool down easier and have difficulties to warm up, being jeopardized by the constraints due to the cold. The warmer preferred body temperatures coupled with the cooler microhabitats and bodies in nature complicate to anticipate how individuals will respond to climate change, but the acclimation to the warmer temperatures led six of them to death, suggesting they had limited tolerance to heat and would be vulnerable to global warming.