Data from: Trade-offs between water loss and gas exchange influence habitat suitability of a woodland salamander

1. Reversible acclimation increases resilience to environmental stress, but acclimation may have hidden costs due to underlying links between related physiological traits. Interactions between physiological traits might result in trade-offs that undermine whole-organism performance if the change in a related trait reduces the net benefits of acclimation or increases susceptibility to alternative environmental stressors. 2. Metabolic rate and water loss rate are two fundamental physiological traits that could interact due to their dependence on gas exchange across shared physical surfaces. Reductions in water loss rate in response to dehydration stress might reduce metabolic rate by constraining the flux of both water and oxygen. 3. We examined acclimation of metabolic rate and water loss rate using a species of woodland salamander (Plethodon metcalfi) in response to temperature and humidity using a full factorial experimental design. We controlled the evaporative demand of the air across temperatures to assess temperature and humidity as independent cues for acclimation. We predicted that reductions in water loss rate would coincide with reductions in metabolic rate in response to temperature due to shared physical and chemical pathways. We also assessed acclimation of heart rates as a potential compensatory mechanism used to promote oxygen delivery. We integrated these responses into a biophysical model developed from first principles to demonstrate the potential for these interactions to influence habitat suitability. 4. We found that reductions of water loss rates during thermal acclimation were associated with simultaneous reductions in metabolic rates, and we did not find a compensatory response in heart rates. We suggest that these linkages underlie whole-organism strategies (e.g., physiological dormancy or arousal) for reducing the energetic costs imposed by warm temperatures. The biophysical model suggested that the interaction between these two traits potentially structures phenotypic variation in our population because certain combinations of trait values were incapable of reaching positive energy balance. 5. Trade-offs between linked physiological traits potentially structure whole-organism strategies for responding to environmental stressors and constrain phenotypic variation.

1. 可逆驯化（reversible acclimation）可提升生物对环境胁迫（environmental stress）的耐受能力，但由于相关生理性状（physiological traits）间存在内在关联，驯化过程往往伴随隐性代价。若某一相关性状的改变降低了驯化的净收益，或是提升了生物对其他环境胁迫的易感性，生理性状间的相互作用可能引发权衡（trade-offs）效应，进而损害整体生物性能。
2. 代谢率（metabolic rate）与失水率（water loss rate）是两类核心生理性状，二者因依赖共享物理界面的气体交换（gas exchange）而产生相互作用。当生物应对脱水胁迫（dehydration stress）时，失水率的降低可能通过限制水与氧的通量，进而降低代谢率。
3. 本研究以梅氏林地蝾螈（Plethodon metcalfi）为研究对象，采用完全因子实验设计（full factorial experimental design），探究其代谢率与失水率对温度和湿度的驯化响应。我们通过控制不同温度下空气的蒸发需求（evaporative demand），将温度与湿度作为独立的驯化触发因子开展评估。基于二者共享的物理与化学通路，我们推测：当生物响应温度变化时，失水率的降低会伴随代谢率的同步下降。此外，我们还检测了心率（heart rate）的驯化情况，以探究其作为促进氧气输送的潜在补偿机制（compensatory mechanism）的可能性。我们将上述响应整合至基于第一性原理（first principles）构建的生物物理模型（biophysical model）中，以阐明这些生理相互作用对栖息地适宜性（habitat suitability）的潜在影响。
4. 研究结果显示，在热驯化（thermal acclimation）过程中，失水率的降低与代谢率的下降显著相关，且未检测到心率的补偿性响应。我们认为，这些性状关联是生物应对高温所引发的能量成本的整体生物策略（如生理休眠或觉醒）的基础。该生物物理模型表明，这两类性状的相互作用可能塑造了研究种群的表型变异（phenotypic variation），因为部分性状值组合无法实现正向能量平衡（energy balance）。
5. 关联生理性状间的权衡效应，可能塑造生物应对环境胁迫的整体生物策略，并限制表型变异的范围。