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).