Buckley Lauren B, Khaliq Imran, Swanson David L, Hof Christian
Department of Biology University of Washington Seattle Washington.
Zoology Department Ghazi University Punjab Pakistan.
Ecol Evol. 2018 Dec 10;8(24):12375-12385. doi: 10.1002/ece3.4537. eCollection 2018 Dec.
Mechanistic approaches for predicting the ranges of endotherms are needed to forecast their responses to environmental change. We test whether physiological constraints on maximum metabolic rate and the factor by which endotherms can elevate their metabolism (metabolic expansibility) influence cold range limits for mammal and bird species. We examine metabolic expansibility at the cold range boundary (ME) and whether species' traits can predict variability in ME and then use ME as an initial approach to project range shifts for 210 mammal and 61 bird species. We find evidence for metabolic constraints: the distributions of metabolic expansibility at the cold range boundary peak at similar values for birds (2.7) and mammals (3.2). The right skewed distributions suggest some species have adapted to elevate or evade metabolic constraints. Mammals exhibit greater skew than birds, consistent with their diverse thermoregulatory adaptations and behaviors. Mammal and bird species that are small and occupy low trophic levels exhibit high levels of ME. Mammals with high ME tend to hibernate or use torpor. Predicted metabolic rates at the cold range boundaries represent large energetic expenditures (>50% of maximum metabolic rates). We project species to shift their cold range boundaries poleward by an average of 3.9° latitude by 2070 if metabolic constraints remain constant. Our analysis suggests that metabolic constraints provide a viable mechanism for initial projections of the cold range boundaries for endotherms. However, errors and approximations in estimating metabolic constraints (e.g., acclimation responses) and evasion of these constraints (e.g., torpor/hibernation, microclimate selection) highlight the need for more detailed, taxa-specific mechanistic models. Even coarse considerations of metabolism will likely lead to improved predictions over exclusively considering thermal tolerance for endotherms.
需要采用预测恒温动物分布范围的机制方法来预测它们对环境变化的反应。我们测试了对最大代谢率的生理限制以及恒温动物提高其新陈代谢的因素（代谢扩展性）是否会影响哺乳动物和鸟类物种的寒冷分布范围界限。我们研究了寒冷分布范围边界处的代谢扩展性（ME），以及物种特征是否能够预测ME的变异性，然后将ME作为一种初步方法来预测210种哺乳动物和61种鸟类物种的分布范围变化。我们发现了代谢限制的证据：鸟类（2.7）和哺乳动物（3.2）在寒冷分布范围边界处的代谢扩展性分布峰值相似。右偏态分布表明一些物种已经适应了提高或规避代谢限制。哺乳动物的偏态比鸟类更大，这与它们多样的体温调节适应和行为一致。体型小且处于低营养级的哺乳动物和鸟类物种表现出较高水平的ME。具有高ME的哺乳动物倾向于冬眠或进入蛰伏状态。在寒冷分布范围边界处预测的代谢率代表了巨大的能量消耗（超过最大代谢率的50%）。如果代谢限制保持不变，我们预计到2070年物种的寒冷分布范围边界将平均向极地移动3.9个纬度。我们的分析表明，代谢限制为恒温动物寒冷分布范围边界的初步预测提供了一种可行的机制。然而，估计代谢限制（例如，驯化反应）和规避这些限制（例如，蛰伏/冬眠、微气候选择）中的误差和近似值突出了需要更详细的、特定分类群的机制模型。即使是对新陈代谢的粗略考虑也可能比仅考虑恒温动物的热耐受性带来更好的预测。
