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Abstract：
Climate change involves increases in mean temperature and changes in temperature variability at multiple temporal scales but research rarely considers these temporal scales. The climate variability hypothesis (CVH) provides a conceptual framework for exploring the potential effects of annual scale thermal variability across climatic zones. The CVH predicts ectotherms in temperate regions tolerate a wider range of temperatures than those in tropical regions in response to greater annual variability in temperate regions. However, various other aspects of thermal regimes (e.g. diel variability), organisms\' size and taxonomic identity are also hypothesised to influence thermal tolerance. Indeed, high temperatures in the tropics have been proposed as constraining organisms\' ability to tolerate a wide range of temperatures, implying that high annual maximum temperatures would be associated with tolerating a narrow range of temperatures. We measured thermal regimes and critical thermal limits (CTmax and CTmin) of freshwater insects in the orders Ephemeroptera (mayflies), Plecoptera (stoneflies) and Trichoptera (caddisflies) along elevation gradients in streams in temperate and tropical regions of eastern Australia and tested the CVH by determining which variables were most correlated with thermal breadth (T br = CTmax - CTmin). Consistent with the CVH, T br tended to increase with increasing annual temperature range. T br also increased with body size and T br was generally wider in Plecoptera than in Ephemeroptera or Trichoptera. We also find some support for a related hypothesis, the climate extreme hypothesis (CEH), particularly for predicting upper thermal limits. We found no evidence that higher annual maximum temperature constrained individuals\' abilities to tolerate a wide range of temperatures. The support for the CVH we document suggests that temperate organisms may be able to tolerate wider ranges of temperatures than tropical organisms. There is an urgent need to investigate other aspects of thermal regimes, such as diel temperature cycling and minimum temperature.
摘要：
气候变化涉及多个时间尺度上平均温度的升高和温度变异性的变化，但研究很少考虑这些时间尺度。气候变异性假设（CVH）为探索跨气候带的年尺度热变异性的潜在影响提供了一个概念框架。CVH预测，由于温带地区的年变化较大，温带地区的外温比热带地区的外温耐受更宽的温度范围。然而,热态的各种其他方面(例如diel可变性)，还假设生物体的大小和分类学身份会影响耐热性。的确,热带地区的高温被认为是限制生物体耐受宽范围温度的能力，这意味着高的年最高温度将与耐受狭窄的温度范围有关。我们测量了星翅目（may蝇）中淡水昆虫的热态和临界热限（CTmax和CTmin），沿澳大利亚东部温带和热带地区溪流的海拔梯度，Plecoptera（石蝇）和Trichoptera（caddisfly），并通过确定哪些变量与热宽度最相关（Tbr=CTmax-CTmin）来测试CVH。与CVH一致，Tbr随着年温度范围的增加而增加。Tbr也随着体型的增加而增加，并且Tbr在Plecoptera中通常比在Ephemeroptera或Trichoptera中更宽。我们还找到了一些相关假设的支持，气候极端假设(CEH)，特别是预测热上限。我们没有发现任何证据表明，较高的年最高温度限制了个体耐受各种温度的能力。我们所记录的对CVH的支持表明，温带生物可能比热带生物能够耐受更宽的温度范围。迫切需要研究热态的其他方面，如diel温度循环和最低温度。
