2. Operative temperature and thermoregulation
We extracted hourly microclimate data for the past (1980-2000) and future (2080-2100; under the RCP 8.5 emission scenario) from a dynamically downscaled dataset, which covered North America at 36 × 36 km resolution (Levy et al. 2016a). We then used a biophysical model to calculate operative temperatures of reproductive females and juveniles in habitats of 0% shade and 100% shade, respectively (see Table S1 for parameters). The biophysical model has previously been applied in studies as a tool for translating microclimates to operative temperature of ectotherms (Buckley 2008; Levy et al. 2016b).
During daylight hours, we allowed individuals to thermoregulate within the range of four potential temperatures: operative temperatures on the ground in 0% and 100% shade and temperatures of burrow (soil temperatures at 6 cm depth) in 0% and 100% shade. Thermoregulating individuals were assumed to achieve body temperatures as close as possible to their preferred body temperatures (Table S1;Sceloporus lizards shows little geographic and between-modes variation of preferred body temperatures (Buckley et al. 2015)). During night hours, their body temperatures were assumed to conform to burrow temperatures in 100% shade. We referred to the number of hours that body temperatures were between 29.4 and 36.3℃ (central 80% of field body temperature (Angilletta 2001)) as “thermal opportunity,” because individuals can feed and digest only with body temperatures in this range (Levy et al. 2017).