DataSheet_1_Physiological cold tolerance evolves faster than climatic niches in plants.docx

Understanding how plants respond to thermal stress is central to predicting plant responses and community dynamics in natural ecosystems under projected scenarios of climate change. Although physiological tolerance is suggested to evolve slower than climatic niches, this comparison remains to be addressed in plants using a phylogenetic comparative approach. In this study, we compared i) the evolutionary rates of physiological tolerance to extreme temperatures with ii) the corresponding rates of climatic niche across three major vascular plant groups. We further accounted for the potential effects of hardening when examining the association between physiological and climatic niche rates. We found that physiological cold tolerance evolves faster than heat tolerance in all three groups. The coldest climatic-niche temperatures evolve faster than the warmest climatic-niche temperatures. Importantly, evolutionary rates of physiological cold tolerance were faster than rates of change in climatic niches. However, an inverse association between physiological cold tolerance and responding climatic niche for plants without hardening was detected. Our results indicated that plants may be sensitive to changes in warmer temperatures due to the slower evolutionary rates of heat tolerance. This pattern has deep implications for the framework that is being used to estimate climate-related extinctions over the upcoming century.

解析植物如何响应热胁迫（thermal stress），是在预估的气候变化情景下，预测自然生态系统中植物响应与群落动态的核心所在。尽管已有研究表明生理耐受性（physiological tolerance）的演化速率慢于气候生态位（climatic niche），但针对植物类群的此类比较仍需通过系统发育比较方法（phylogenetic comparative approach）开展相关研究。本研究针对三大维管植物（vascular plant）类群，对比了两项指标的演化速率：其一为极端温度相关生理耐受性的演化速率，其二为对应气候生态位的演化速率。我们在探究生理耐受性与气候生态位速率之间的关联时，进一步考量了驯化作用（hardening）的潜在影响。研究发现，在所有三大类群中，植物的生理耐寒性演化速率均快于耐热性。气候生态位的最冷临界温度的演化速率快于最热临界温度。尤为重要的是，生理耐寒性的演化速率快于气候生态位的变化速率。但研究发现，未经过驯化作用的植株，其生理耐寒性与响应性气候生态位之间呈负相关关联。本研究结果表明，由于耐热性演化速率较慢，植物可能对温度升高的变化更为敏感。该研究结果对于当前用于预估未来百年气候相关性灭绝的研究框架具有重要启示意义。