Protection from overheating of simulated Sceloporus horridus lizards in a biosphere reserve of seasonally dry tropical forest in central Mexico

To determine whether in general protected areas provide protection from overheating for the lizard populations inhabiting them, we compared the effect of a protected area on vegetation cover, and in turn on the microclimate experienced by lizards, at their spatial scale and considering their thermoregulatory behaviors. We used remote sensing and a mechanistic niche model (NicheMapR) to test whether the Sierra de Huautla Biosphere Reserve (REBIOSH) had higher vegetation cover, cooler microclimate, higher thermal safety margin (TSM), higher foraging duration, and lower basal metabolic rate for simulated Sceloporus horridus lizards, compared to adjacent unprotected areas to the north (NAA) and south (SAA) in 1999—when the reserve was declared—and 2020—20 years after the declaration. The study area is in south-central Mexico and the considered surface is mainly occupied by seasonally dry tropical forest. Within each polygon, we randomly placed 150 sampling points from where we quantified our study variables. The sampling points have a spatial resolution of 30 m. We characterized the vegetation cover using the normalized difference vegetation index (NDVI) * 100, that is to say, converted to a percentage. We simulated the microclimate at 3cm or 120cm perch height because the latter may be cooler than the former and because S. horridus moves along such interval. We calculated the TSM as the voluntary thermal maximum of the species (36.4°C) minus the mean body temperature of the simulated lizard. In the simulation, we allowed the following thermoregulatory behaviors: changing its body orientation relative to direct insolation, moving along the specified interval of shade percentage, and climbing from 3cm up to 120cm perch height. Each combination of levels of perch height, year, season, and polygon had a sample size of 150 records. We compared the vegetation cover in three months of the rainy season, and the microclimate temperature, TSM, foraging duration, and basal metabolic rate in three months of the dry season.
Note: Data from a resubmitted research to be published in Journal of Thermal Biology.