Hopkins Marine Station, Department of Biology, Stanford University, Pacific Grove, CA 93950, USA.
J Exp Biol. 2010 Mar 15;213(6):912-20. doi: 10.1242/jeb.037473.
Physiological studies can help predict effects of climate change through determining which species currently live closest to their upper thermal tolerance limits, which physiological systems set these limits, and how species differ in acclimatization capacities for modifying their thermal tolerances. Reductionist studies at the molecular level can contribute to this analysis by revealing how much change in sequence is needed to adapt proteins to warmer temperatures--thus providing insights into potential rates of adaptive evolution--and determining how the contents of genomes--protein-coding genes and gene regulatory mechanisms--influence capacities for adapting to acute and long-term increases in temperature. Studies of congeneric invertebrates from thermally stressful rocky intertidal habitats have shown that warm-adapted congeners are most susceptible to local extinctions because their acute upper thermal limits (LT(50) values) lie near current thermal maxima and their abilities to increase thermal tolerance through acclimation are limited. Collapse of cardiac function may underlie acute and longer-term thermal limits. Local extinctions from heat death may be offset by in-migration of genetically warm-adapted conspecifics from mid-latitude 'hot spots', where midday low tides in summer select for heat tolerance. A single amino acid replacement is sufficient to adapt a protein to a new thermal range. More challenging to adaptive evolution are lesions in genomes of stenotherms like Antarctic marine ectotherms, which have lost protein-coding genes and gene regulatory mechanisms needed for coping with rising temperature. These extreme stenotherms, along with warm-adapted eurytherms living near their thermal limits, may be the major 'losers' from climate change.
生理研究可以通过确定哪些物种目前生活在接近其最高热耐受极限的地方，哪些生理系统设定了这些极限，以及物种在改变其热耐受能力的适应能力方面有何差异，来帮助预测气候变化的影响。分子水平的简化研究可以通过揭示适应蛋白质适应温暖温度需要多少序列变化来为这种分析做出贡献，从而提供对潜在适应进化速度的深入了解，并确定基因组的内容（蛋白质编码基因和基因调控机制）如何影响适应急性和长期温度升高的能力。来自热应激岩石潮间带栖息地的同属无脊椎动物的研究表明，适应温暖的同属种最容易灭绝，因为它们的急性上限热极限（LT(50) 值）接近当前的热最大值，并且它们通过适应来增加热耐受性的能力是有限的。心脏功能的崩溃可能是急性和长期热极限的基础。热死亡导致的局部灭绝可能会被从中纬度“热点”地区遗传上适应温暖的同种个体的迁入所抵消，因为夏季中午低潮会选择耐热性。单一氨基酸替换足以使蛋白质适应新的热范围。对于像南极海洋变温动物这样的基因组损伤来说，适应进化更具挑战性，它们失去了适应不断上升温度所需的蛋白质编码基因和基因调控机制。这些极端的变温动物，以及生活在接近其热极限的适应温暖的广温动物，可能是气候变化的主要“输家”。
