Data from: Environmental conditions shape the temporal pattern of investment in reproduction and survival

The relationship between environmental stress exposure and ageing is likely to vary with stressor severity, life history stage, and the time scale over which effects are measured. Such factors could influence whether stress exposure accelerates or slows the ageing process, but their interactions have not previously been experimentally investigated. We found that experimental exposure of zebra finches to mildly challenging environmental circumstances from young to old adulthood, which increased exposure to stress hormones, reduced breeding performance during early adulthood, but had positive effects when individuals were bred in old adulthood. This difference was not due to selective mortality, since the effects were evident within individuals, and no evidence of habituation in the response to the stressor was found. The more stressful environment had no effects on survival during young or old adulthood, but substantially improved survival during middle age. Changes in the effects at different ages could be due to the duration and nature of the challenging exposure, or to variation in coping capacity or strategy with age. These results show that living under challenging environmental circumstances can influence ageing trajectories in terms of both reproductive performance and longevity. Our results provide experimental support for the emerging idea that stress exposure needs to be optimised rather than minimised to obtain the best health outcomes.

环境应激暴露与衰老之间的关联，大概率会随应激源强度、生命史阶段以及效应测量的时间尺度发生变化。此类因素可能会决定应激暴露是加速还是延缓衰老进程，但此前尚未有实验针对这些因素的交互作用展开研究。我们通过实验发现，将斑胸草雀（zebra finches）从青年成年期至老年成年期持续暴露于轻度挑战性环境中——该环境会提升个体的应激激素暴露水平——会降低其在青年成年期的繁殖表现，但当个体进入老年成年期进行繁殖时，则会产生积极影响。该差异并非源于选择性死亡，因为上述效应在个体内部均有体现，且未观察到对应激源产生习惯化的证据。强度更高的挑战性环境，对青年或老年成年期的存活率无显著影响，但在中年阶段显著提升了存活率。不同年龄阶段所呈现的效应差异，可能源于挑战性暴露的持续时间与性质，或是随年龄增长而变化的应对能力或应对策略。上述结果表明，处于挑战性环境中，可从繁殖性能与寿命两个维度影响衰老轨迹。我们的研究结果为新兴观点提供了实验支撑：若要获得最佳健康结局，需对应激暴露进行优化而非单纯最小化。