Data from: Telomere attrition and growth: a life-history framework and case study in common terns

The relationship between growth and age-specific telomere length, as a proxy of somatic state, is increasingly investigated, but observed patterns vary and a predictive framework is lacking. We outline expectations based on the assumption that telomere maintenance is costly and argue that individual heterogeneity in resource acquisition is predicted to lead to positive covariance between growth and telomere length. However, canalization of resource allocation to the trait with a larger effect on fitness, rendering that trait relatively invariant, can cause the absence of covariance. In a case study of common tern (Sterna hirundo) chicks, in which hatching order is the main determinant of variation in resource acquisition within broods, we find that body mass, but not telomere length or attrition, varies with hatching order. Moreover, body mass and growth positively predict survival to fledging, whereas telomere length and attrition do not. Using a novel statistical method to quantify standardized variance in plasticity, we estimate between-individual variation in telomere attrition to be only 12% of that of growth. Consistent with the relative invariance of telomere attrition, we find no correlation between age-specific body mass or growth and telomere attrition. We suggest that common tern chicks prioritize investment in long-term somatic state (as indicated by canalization of telomere maintenance) over immediate survival benefits of growth as part of an efficient brood reduction strategy that benefits the parents. As such, inter-specific variation in the growth-telomere length relationship may be explained by the extent to which parents benefit from rapid mortality of excess offspring.

生长与作为躯体状态替代指标的年龄特异性端粒长度（telomere length）之间的关联正受到越来越多的研究关注，但已有观测结果呈现出分歧，且目前缺乏统一的预测性框架。我们基于端粒维持存在能量成本这一前提梳理了相关理论预期，并提出：个体间资源获取的异质性预计会导致生长速率与端粒长度之间呈现正协变关系。然而，若对适合度（fitness）影响更大的性状实施资源分配的稳态化调控，使该性状相对恒定，则可能导致二者间无协变关系。在针对普通燕鸥（Sterna hirundo）雏鸟的案例研究中——其窝内雏鸟资源获取差异的核心决定因素为孵化顺序——我们发现，雏鸟的体重会随孵化顺序发生变化，但端粒长度与端粒损耗并未呈现此种差异。此外，雏鸟的体重及其生长速率可正向预测其离巢存活率，而端粒长度与端粒损耗则不具备此种预测能力。我们采用一种用于量化可塑性标准化方差的新型统计方法，估算得出个体间端粒损耗的变异程度仅为生长速率变异的12%。与端粒损耗相对恒定的结论一致，我们未观测到年龄特异性体重或生长速率与端粒损耗之间存在相关性。我们提出，普通燕鸥雏鸟会优先将资源投入到长期躯体状态的维持（以端粒维持的稳态化调控为表征），而非生长带来的即时生存收益，这属于一种可使亲代获益的高效窝雏减少策略。据此，不同物种间生长与端粒长度之间关联的差异，或许可以通过亲代从过剩子代快速死亡中获益的程度来解释。