Data from: Untangling the roles of microclimate, behavior 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 behavioral thermoregulation. To understand interactions among these variables, we analyzed 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 behavioral 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 behavioral 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.

生物地理分布由小尺度过程的累积效应所驱动。因此，动物对热胁迫的易感性，是其对体温（body temperature, Tb）、微气候条件以及行为体温调节的生理敏感性共同作用的结果。为厘清这些变量间的相互作用机制，我们分析了中国沿海不同纬度带的3种潮间带螺类的耐热性，并估算了各采样点不同微生境下的潜在体温。随后我们通过实验测定了两个临界温度：一是体温随温度升高急剧下降时的阿伦尼乌斯拐点温度（Arrhenius Breakpoint Temperature, ABT），二是心跳完全停止时的平线温度（Flat Line Temperature, FLT），并据此计算得到热安全裕度（Thermal Safety Margins, TSM）。模型预测，仅在一个中纬度采样点的向阳微生境中，会频繁出现超过FLT的致死性高温。然而，多数采样点的向阳微生境中，部分个体的ABT已被超出，这表明行为体温调节能力较差的螺类会出现生理损伤，同时也揭示了耐热极限的个体间差异（inter-individual variations）与生理多态性（physiological polymorphism）。对体温的自相关分析显示，极端温度的可预测性在最热的采样点中最低，这意味着行为体温调节的有效性在这些位点可能最差。本研究结果表明，在预测气候变化的影响时，小空间尺度的机制性研究发挥着至关重要的作用。