Charmantier Anne, Perrins Christopher, McCleery Robin H, Sheldon Ben C
Edward Grey Institute, Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, United Kingdom.
Proc Natl Acad Sci U S A. 2006 Apr 25;103(17):6587-92. doi: 10.1073/pnas.0511123103. Epub 2006 Apr 17.
Why do individuals stop reproducing after a certain age, and how is this age determined? The antagonistic pleiotropy theory for the evolution of senescence predicts that increased early-life performance should be accompanied by earlier (or faster) senescence. Hence, an individual that has started to breed early should also lose its reproductive capacities early. We investigate here the relationship between age at first reproduction (AFR) and age at last reproduction (ALR) in a free-ranging mute swan (Cygnus olor) population monitored for 36 years. Using multivariate analyses on the longitudinal data, we show that both traits are strongly selected in opposite directions. Analysis of the phenotypic covariance between these characters shows that individuals vary in their inherent quality, such that some individuals have earlier AFR and later ALR than expected. Quantitative genetic pedigree analyses show that both traits possess additive genetic variance but also that AFR and ALR are positively genetically correlated. Hence, although both traits display heritable variation and are under opposing directional selection, their evolution is constrained by a strong evolutionary tradeoff. These results are consistent with the theory that increased early-life performance comes with faster senescence because of genetic tradeoffs.
为什么个体在一定年龄后会停止繁殖，以及这个年龄是如何确定的？衰老进化的拮抗多效性理论预测，早期生活表现的提高应该伴随着更早（或更快）的衰老。因此，早繁殖的个体也应该早丧失繁殖能力。我们在此研究了在一个被监测了36年的自由放养疣鼻天鹅（Cygnus olor）种群中，首次繁殖年龄（AFR）和末次繁殖年龄（ALR）之间的关系。通过对纵向数据进行多变量分析，我们表明这两个性状在相反方向上受到强烈选择。对这些性状之间表型协方差的分析表明，个体在其内在质量上存在差异，使得一些个体的AFR比预期的早，而ALR比预期的晚。定量遗传谱系分析表明，这两个性状都具有加性遗传方差，但AFR和ALR在遗传上呈正相关。因此，尽管这两个性状都表现出可遗传的变异并且受到相反方向的定向选择，但它们的进化受到强烈的进化权衡的限制。这些结果与以下理论一致，即由于遗传权衡，早期生活表现的提高伴随着更快的衰老。
