Data from: Untangling the roles of microclimate, behaviour and physiological polymorphism in governing vulnerability of intertidal snails to heat stress

Biogeographic distributions are driven by cumulative effects of smaller
scale processes. Thus, vulnerability of animals to thermal stress is the
result of physiological sensitivities to body temperature (Tb),
microclimatic conditions, and behavioural thermoregulation. To understand
interactions among these variables, we analysed the thermal tolerances of
three species of intertidal snails from different latitudes along the
Chinese coast, and estimated potential Tb in different microhabitats at
each site. We then empirically determined the temperatures at which heart
rate decreased sharply with rising temperature (Arrhenius breakpoint
temperature, ABT) and at which it fell to zero (flat line temperature,
FLT) to calculate thermal safety margins (TSM). Regular exceedance of FLT
in sun-exposed microhabitats, a lethal effect, was predicted for only one
mid-latitude site. However, ABTs of some individuals were exceeded at
sun-exposed microhabitats in most sites, suggesting physiological
impairment for snails with poor behavioural thermoregulation and revealing
inter-individual variations (physiological polymorphism) of thermal
limits. An autocorrelation analysis of Tb showed that predictability of
extreme temperatures was lowest at the hottest sites, indicating that the
effectiveness of behavioural thermoregulation is potentially lowest at
these sites. These results illustrate the critical roles of mechanistic
studies at small spatial scales when predicting effects of climate change.