Data from: The impact of reproductive investment and early-life environmental conditions on senescence: support for the disposable soma hypothesis

Several hypotheses have been put forward to explain the evolution of senescence. One of the leading hypotheses, the disposable soma hypothesis, predicts a trade-off, whereby early-life investment in reproduction leads to late-life declines in survival (survival senescence). Testing this hypothesis in natural populations is challenging, but important for understanding the evolution of senescence. We used the long-term data set from a contained, predator-free population of individually marked Seychelles warblers (Acrocephalus sechellensis) to investigate how age-related declines in survival are affected by early-life investment in reproduction and early-life environmental conditions. The disposable soma hypothesis predicts that higher investment in reproduction, or experiencing harsh conditions during early life, will lead to an earlier onset, and an increased rate, of senescence. We found that both sexes showed similar age-related declines in late-life survival consistent with senescence. Individuals that started breeding at a later age showed a delay in survival senescence, but this later onset of breeding did not result in a less rapid decline in late-life survival. Although survival senescence was not directly related to early-life environmental conditions, age of first breeding increased with natal food availability. Therefore, early-life food availability may affect senescence by influencing age of first breeding. The disposable soma hypothesis of senescence is supported by delayed senescence in individuals that started breeding at a later age and therefore invested less in reproduction.

学界已提出多种假说以阐释衰老（senescence）的演化机制。其中主流假说之一的体细胞冗余假说（disposable soma hypothesis）预言了一种权衡效应：生命早期对繁殖的投入，会导致生命后期的存活能力下降，即存活衰老（survival senescence）。在自然种群中验证该假说颇具挑战，但对于理解衰老的演化至关重要。本研究借助来自封闭隔离、无捕食者的个体标记塞舌尔莺（Acrocephalus sechellensis）种群的长期数据集，探究生命早期的繁殖投入与早期环境条件如何影响存活能力的年龄相关性下降。体细胞冗余假说预言：更高的繁殖投入，或生命早期经历恶劣环境，会导致衰老更早启动且速率更快。研究发现，两性均表现出与衰老相符的生命后期存活能力年龄相关性下降。较晚开始繁殖的个体，其存活衰老出现延迟，但较晚的繁殖起始并未带来生命后期存活能力下降速率的减缓。尽管存活衰老与早期环境条件并无直接关联，但首次繁殖年龄会随出生巢区的食物可获得性升高而增加。因此，生命早期的食物可获得性或通过影响首次繁殖年龄，进而作用于衰老进程。较晚开始繁殖、因此繁殖投入更少的个体，其衰老进程出现延迟，这一结果支持了衰老的体细胞冗余假说。