Data from: Independence among physiological traits suggests flexibility in the face of ecological demands on phenotypes

Phenotypic flexibility allows animals to adjust their physiology to diverse environmental conditions encountered over the year. Examining how these varying traits covary gives insights into potential constraints or freedoms that may shape evolutionary trajectories. In this study we examined relationships among hematocrit, baseline corticosterone concentration, constitutive immune function and basal metabolic rate in red knot Calidris canutus islandica individuals subjected to experimentally manipulated temperature treatments over an entire annual cycle. If covariation among traits is constrained, we predict consistent covariation within and among individuals. We further predict consistent correlations between physiological and metabolic traits if constraints underlie species level patterns found along the slow-fast pace-of-life continuum. We found no consistent correlations among hematocrit, baseline corticosterone concentration, immune function and basal metabolic rate either within or among individuals. This provides no evidence for constraints limiting relationships among these measures of the cardiovascular, endocrine, immune and metabolic systems in individual red knots. Rather, our data suggest that knots are free to adjust individual parts of their physiology independently. This makes good sense if one places the animal within its ecological context where different aspects of the environment might put different pressures on different aspects of physiology.

表型灵活性（phenotypic flexibility）使动物能够根据全年遭遇的多样环境条件调整自身生理状态。探究这些可变性状间的协变关系，能够揭示可能塑造演化轨迹的潜在约束与自由度。本研究针对经历了全年度实验性温度调控处理的红腹滨鹬冰岛亚种（Calidris canutus islandica）个体，探究了血细胞比容（hematocrit）、基础皮质酮浓度（baseline corticosterone concentration）、固有免疫功能（constitutive immune function）与基础代谢率（basal metabolic rate）之间的关联。若性状间的协变关系存在约束，则我们预测个体内部及个体间均会呈现稳定的协变模式。此外，若沿生活史快慢连续体（slow-fast pace-of-life continuum）分布的物种类群模式由约束机制主导，则我们预测生理性状与代谢性状间会存在稳定的相关性。本研究未发现血细胞比容、基础皮质酮浓度、免疫功能与基础代谢率之间在个体内部或个体间存在稳定的相关性。这表明并无证据表明，红腹滨鹬个体的心血管、内分泌、免疫与代谢系统相关指标间的关联受到约束。相反，我们的数据表明，红腹滨鹬能够独立自由地调控自身生理状态的各个组分。若将动物置于其生态背景中考量——即环境的不同维度会对生理的不同方面施加差异化选择压力——这一结果便合情合理。