Data from: Within-individual plasticity explains age-related decrease in stress response in a short-lived bird

A crucial problem for every organism is how to allocate energy between competing life-history components. The optimal allocation decision is often state-dependent and mediated by hormones. Here, we investigated how age, a major state variable affects individuals' hormonal response to a standardized stressor: a trait that may reflect allocation between self-maintenance and reproduction. We caught free-living house sparrows and measured their hormonal (corticosterone) response to capture stress in consecutive years. Using a long-term ringing dataset, we determined the age of the birds, and we partitioned the variation into within- and among-individual age components to investigate the effects of plasticity versus selection or gene flow, respectively, on the stress response. We found large among-individual variation in the birds' hormone profiles, but overall, birds responded less strongly to capture stress as they grew older. These results suggest that stress responsiveness is a plastic trait that may vary within individuals in an adaptive manner, and natural selection may act on the reaction norms producing optimal phenotypic response in the actual environment and life-history stage.

所有生物体都面临的核心难题之一，是如何在相互竞争的生活史组分之间分配能量。最优分配决策通常依赖于个体状态，并由激素介导调控。本研究聚焦于作为核心状态变量的年龄，如何影响个体对标准化应激源的激素响应——这一性状可反映个体在自我维持与繁殖之间的能量分配策略。我们捕捉野外自由栖息的家麻雀，并连续多年测定其皮质酮（corticosterone）对捕获应激的响应水平。我们借助长期鸟类环志数据集确定了受试家麻雀的年龄，并将应激响应的变异划分为个体内与个体间年龄组分，以分别探究表型可塑性、自然选择及基因流对该应激响应的影响。研究发现，家麻雀的激素表型存在显著的个体间变异，但整体而言，随着年龄增长，个体对捕获应激的响应强度逐渐降低。上述结果表明，应激响应性属于可塑性性状，可在个体内以适应性方式发生变化；同时自然选择可能作用于反应规范，使其在实际环境与生活史阶段中产生最优表型响应。