Marine Biology and Ecology Research Centre, School of Biological and Marine Sciences, University of Plymouth, Drake Circus Plymouth, PL4 8AA, UK.
Department of Animal Ecology and Physiology, Radboud Institute for Biological and Environmental Sciences (RIBES), Radboud University, PO Box 9010, 6500 GL, Heyendaalseweg 135, 6525, AJ, Nijmegen, the Netherlands.
J Therm Biol. 2021 Dec;102:103113. doi: 10.1016/j.jtherbio.2021.103113. Epub 2021 Oct 22.
Thermal history can plastically alter the response of ectotherms to temperature, and thermal performance curves (TPCs) are powerful tools for exploring how organismal-level performance varies with temperature. Plasticity in TPCs may be favoured in thermally variable habitats, where it can result in fitness benefits. However, thermal physiology remains insufficiently studied for freshwater insects despite freshwater biodiversity being at great risk under global change. Here, we assess how acclimation at either summer or winter average temperatures changes TPCs for locomotion activity and metabolism in Enochrus jesusarribasi (Hydrophilidae), a water beetle endemic to shallow saline streams in SE Spain. This beetle is a bimodal gas exchanger and so we also assessed how aerial and aquatic gas exchange varied across temperatures for both acclimation treatments. Responses of locomotory TPCs to thermal acclimation were relatively weak, but high temperature acclimated beetles tended to exhibit higher maximum locomotor activity and reduced TPC breadth than those acclimated at lower temperature. High temperature acclimation increased the thermal sensitivity of metabolic rates, contrary to the response generally found in aquatic organisms. Higher metabolic rates upon high temperature acclimation were achieved by increasing aerial, rather than aquatic oxygen uptake. Such plastic respiratory behaviour likely contributed to enhanced locomotor performance at temperatures around the optimum and thermal plasticity could thus be an important component in the response of aquatic insects to climate change. However, high temperature acclimation appeared to be detrimental for locomotion in subsequent exposure at upper sublethal temperatures, suggesting that this narrow range endemic may be vulnerable to future climate warming. This study demonstrates that TPCs are context-specific, differing with performance metric as well as thermal history. Such context dependency must be considered when using TPCs to predict organismal responses to climate change.
热历史可以使变温动物对温度的反应产生塑性变化，而热性能曲线 (TPC) 是探索生物体水平性能随温度变化的有力工具。在温度变化的栖息地中，TPC 的可塑性可能更有利，因为它可以带来适应度的好处。然而，尽管全球变化下淡水生物多样性面临巨大风险，但淡水昆虫的热生理学仍研究不足。在这里，我们评估了在夏季或冬季平均温度下适应如何改变西班牙东南部浅水咸水河特有水甲虫 Enochrus jesusarribasi 的运动活性和代谢的 TPC。这种甲虫是一种双模态气体交换器，因此我们还评估了两种适应处理下空气和水的气体交换如何随温度变化。对热适应的运动 TPC 的反应相对较弱，但高温适应的甲虫往往表现出比低温适应的甲虫更高的最大运动活性和更窄的 TPC 宽度。与水生生物通常发现的反应相反，高温适应增加了代谢率的热敏感性。通过增加空气而非水的氧气摄取来实现高温适应下更高的代谢率。这种有弹性的呼吸行为可能有助于在最佳温度附近提高运动性能，因此热可塑性可能是水生昆虫对气候变化的反应的一个重要组成部分。然而，高温适应似乎对后续在较高亚致死温度下的运动不利，这表明这种狭窄范围的特有种可能容易受到未来气候变暖的影响。本研究表明，TPC 是特定于上下文的，与性能指标以及热历史有关。在使用 TPC 预测生物体对气候变化的反应时，必须考虑这种上下文依赖性。
