The Effects of Thermal Opportunity and Habitat on Physiological Performance in Ecologically Distinct Populations of the Florida Scrub Lizard Sceloporus woodi

An ectotherm’s ability to thermoregulate affects many physiological traits. Therefore, thermal factors are paramount when considering behavior, activity time, body temperatures, energy budget, and performance capabilities. The Florida scrub lizard (Sceloporus woodi) is a ground-dwelling lizard that occupies longleaf pine and sand pine scrub habitats in the Ocala National Forest. Here, this species’ habitat is maintained by either clear-cut logging in scrub stands, or prescribed burning in long leaf pine stands. These habitat types differ in their dominant vegetation, canopy cover, and availability of vertical perches and thus are ecologically different. I used biophysical models to measure the available environmental temperatures in longleaf pine and sand pine scrub populations. Thermal opportunity is used to describe the availability of preferred temperatures within specific habitats so as to understand the thermal constraints that may influence available activity times as well as the energy and resources spent on thermoregulation in a given environment. Longleaf pine populations had higher thermal opportunity which allowed populations to thermoregulate more effectively overall. However, when thermal quality of habitat was poor, all populations increased thermoregulatory effort despite the higher costs of thermoregulating. Furthermore, the difference in available temperature distribution in each environment was examined in the context of the thermal sensitivity of locomotor performance. Thermal performance curves were generated to compare traits associated with physiological performance. Higher operative temperatures in sand pine scrub habitats were correlated with higher critical thermal limits and thermal optima in these populations. Despite the range of preferred temperatures being the same, the data suggest that the thermal physiology of this species is evolutionarily labile. Thus, variation in thermal opportunity between longleaf pine and sand pine scrub stands is likely driving the observed divergence in thermal physiology among these populations