Data from: Linking species thermal tolerance to elevational range shifts in upland dung beetles

Climate warming has been proposed as the main cause of the recent range shifts seen in many species. Although species' thermal tolerances are thought to play a key role in determining responses to climate change, especially in ectotherms, empirical evidence is still limited. We investigate the connection between species' thermal tolerances, elevational range and shifts in the lower elevational limit of dung beetle species (Coleoptera, Aphodiidea) in an upland region in the northwest of England. We measured thermal tolerances in the laboratory, and used current and historical distribution data to test specific hypotheses about the area's three dominant species, particularly the species most likely to suffer from warming: Agollinus lapponum. We found marked differences between species in their minimum and maximum thermal tolerance and in their elevational range and patterns of abundance. Overall, differences in thermal limits among species matched the abundance patterns along the elevation gradient expected if distributions were constrained by climate. A. lapponum abundance increased with elevation and this species showed lower maximum and minimum thermal limits than Acrossus depressus, for which abundance declined with elevation. Consistent with lower tolerance to high temperature, we recorded an uphill retreat of the low elevation limit of A. lapponum (177 m over 57 years) in line with the increase in summer temperature observed in the region over the same period. Moreover, this species has been replaced at low and mid-elevations by the other two warm-tolerant species (A. depressus and Agrilinus ater). Our results provide empirical evidence that species' thermal tolerance constrains elevational ranges and contributes to explain the observed responses to climate warming. A mechanistic understanding of how climate change directly affects species, such as the one presented here, will provide a robust base to inform predictions of how individual species and whole assemblages may change in the future.

气候变暖被认为是当前诸多物种分布范围发生改变的主要诱因。尽管物种的热耐受性被认为在决定其应对气候变化的响应中发挥关键作用，尤其对于变温动物而言，但相关实证证据仍较为匮乏。本研究以英格兰西北部一高地地区的蜣螂（鞘翅目Coleoptera，蜉金龟总科Aphodiidea）物种为研究对象，探究其热耐受性、海拔分布范围与海拔下限迁移之间的关联。我们在实验室中测定了这些物种的热耐受性，并结合当前与历史分布数据，针对该区域的三种优势物种——尤其是最易受气候变暖影响的Agollinus lapponum——检验了特定假说。研究发现，不同物种的最低、最高热耐受性，以及其海拔分布范围和种群丰度模式均存在显著差异。总体而言，若物种分布受气候条件制约，物种间的热极限差异与沿海拔梯度的丰度模式相符。A. lapponum的种群丰度随海拔升高而增加，且其最高与最低热耐受性均低于Acrossus depressus——后者的种群丰度随海拔升高而降低。与该物种对高温耐受性较弱的结论一致，我们观测到A. lapponum的海拔下限向高海拔迁移（57年间上移177米），这与同期该区域夏季气温的上升趋势相符。此外，在低海拔与中海拔区域，该物种已被另外两种耐热物种（A. depressus与Agrilinus ater）所取代。本研究结果提供了实证证据，表明物种的热耐受性会制约其海拔分布范围，有助于解释观测到的物种对气候变暖的响应。诸如本研究这般对气候变化如何直接影响物种的机制性理解，将为预测单个物种乃至整个物种组合未来的变化趋势提供坚实的理论基础。