A comparative study of preferred body temperatures and critical thermal tolerance limits among populations of Zootoca vivipara (Squamata : Lacertidae) along an altitudinal gradient

We compared preferred body temperatures, critical thermal minima, and maxim a, and tolerance ranges among four populations of Zootoca vivipara (formerl y Lacerta vivipara) distributed along an altitudinal gradient (250-1450 m) to examine whether different thermal environments have induced a change in these thermal characteristics. Lizards in all populations had similar prefe rred body temperatures and critical thermal limits, suggesting that acclima tion or adaptation of these traits to different thermal environments did no t occur. Subadult females and gravid females preferred lower body temperatu res than nongravid females and subadult and adult males. Preferred body tem peratures differed among individuals of the same age and sex within a parti cular population. In contrast to the negligible among-population variation, preferred body temperatures varied considerably within populations in Z. v ivipara.