Vedder O, Verhulst S, Bauch C, Bouwhuis S
Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands.
Institute of Avian Research, Wilhelmshaven, Germany.
J Evol Biol. 2017 Jul;30(7):1409-1419. doi: 10.1111/jeb.13119. Epub 2017 Jun 10.
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, interspecific variation in the growth-telomere length relationship may be explained by the extent to which parents benefit from rapid mortality of excess offspring.
作为体细胞状态的一个指标，生长与特定年龄的端粒长度之间的关系正受到越来越多的研究，但观察到的模式各不相同，且缺乏一个预测框架。我们基于端粒维持成本高昂这一假设概述了预期，并认为资源获取方面的个体异质性预计会导致生长与端粒长度之间出现正协方差。然而，将资源分配到对适合度影响更大的性状上的渠道化，使得该性状相对不变，可能会导致协方差的缺失。在一项关于普通燕鸥（Sterna hirundo）雏鸟的案例研究中，孵化顺序是一窝雏鸟中资源获取变化的主要决定因素，我们发现体重随孵化顺序而变化，但端粒长度或损耗情况并非如此。此外，体重和生长对雏鸟存活到羽翼丰满有正向预测作用，而端粒长度和损耗情况则不然。我们使用一种新颖的统计方法来量化可塑性的标准化方差，估计端粒损耗的个体间差异仅为生长差异的12%。与端粒损耗的相对不变性一致，我们发现特定年龄的体重或生长与端粒损耗之间没有相关性。我们认为，普通燕鸥雏鸟将对长期体细胞状态的投资（如通过端粒维持的渠道化所表明的）置于生长带来的即时生存益处之上，这是一种有利于亲鸟的高效减少育雏策略的一部分。因此，生长与端粒长度关系的种间差异可能由亲鸟从过多后代的快速死亡中获益的程度来解释。
