Stoffels Rick J, Richardson Adam J, Vogel Matthew T, Coates Simon P, Müller Warren J
CSIRO Land and Water, Murray-Darling Freshwater Research Centre, La Trobe University, Wodonga, VIC, Australia.
Department of Ecology, Environment and Evolution, La Trobe University, Wodonga, VIC, Australia.
Oecologia. 2016 Jan;180(1):45-54. doi: 10.1007/s00442-015-3463-7. Epub 2015 Oct 6.
Humans are rapidly altering thermal landscapes, so a central challenge to organismal ecologists is to better understand the thermal niches of ectotherms. However, there is much disagreement over how we should go about this. Some ecologists assume that a statistical model of abundance as a function of habitat temperature provides a sufficient approximation of the thermal niche, but ecophysiologists have shown that the relationship between fitness and temperature can be complicated, and have stressed the need to elucidate the causal mechanisms underlying the response of species to thermal change. Towards this end, we studied the distribution of two crayfishes, Euastacus woiwuru and Euastacus armatus, along an altitudinal gradient, and for both species conducted experiments to determine the temperature-dependence of: (1) aerobic scope (the difference between maximum and basal metabolic rate; purported to be a proxy of the thermal niche); and (2) burst locomotor performance (primarily fuelled using anaerobic pathways). E. woiwuru occupied cooler habitats than E. armatus, but we found no difference in aerobic scope between these species. In contrast, locomotor performance curves differed significantly and strongly between species, with peak locomotor performances of E. woiwuru and E. armatus occurring at ~10 and ~18 °C, respectively. Crayfish from different thermal landscapes may have similar aerobic thermal performance curves but different anaerobic thermal performance curves. Our results support a growing body of literature implying different components of ectotherm fitness have different thermal performance curves, and further challenge our understanding of the ecology and evolution of thermal niches.
人类正在迅速改变热环境，因此，对于生物有机体生态学家来说，一项核心挑战是要更好地了解变温动物的热生态位。然而，对于我们应该如何开展这项工作，存在很多分歧。一些生态学家认为，将丰度作为栖息地温度的函数的统计模型能够充分近似热生态位，但生态生理学家已经表明，适合度与温度之间的关系可能很复杂，并强调需要阐明物种对热变化响应背后的因果机制。为此，我们研究了两种小龙虾，即沃氏真螯虾（Euastacus woiwuru）和武装真螯虾（Euastacus armatus）沿海拔梯度的分布情况，并针对这两个物种进行了实验，以确定以下方面的温度依赖性：（1）有氧代谢范围（最大代谢率与基础代谢率之间的差异；据称是热生态位的一个指标）；以及（2）爆发式运动表现（主要通过无氧途径提供能量）。沃氏真螯虾占据的栖息地比武装真螯虾更凉爽，但我们发现这两个物种在有氧代谢范围上没有差异。相比之下，不同物种之间的运动表现曲线存在显著且强烈的差异，沃氏真螯虾和武装真螯虾的最大运动表现分别出现在约10℃和约18℃。来自不同热环境的小龙虾可能具有相似的有氧热表现曲线，但无氧热表现曲线不同。我们的研究结果支持了越来越多的文献观点，即变温动物适合度的不同组成部分具有不同的热表现曲线，并进一步挑战了我们对热生态位的生态学和进化的理解。
