Wilson Alastair J, Nussey Daniel H, Pemberton Josephine M, Pilkington Jill G, Morris Alison, Pelletier Fanie, Clutton-Brock Timothy H, Kruuk Loeske E B
Institute of Evolutionary Biology, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JT, United Kingdom.
Curr Biol. 2007 Dec 18;17(24):2136-42. doi: 10.1016/j.cub.2007.11.043.
Aging, or senescence, defined as a decline in physiological function with age, has long been a focus of research interest for evolutionary biologists. How has natural selection failed to remove genetic effects responsible for such reduced fitness among older individuals? Current evolutionary theory explains this phenomenon by showing that, as a result of the risk of death from environmental causes that individuals experience, the force of selection inevitably weakens with age. This in turn means that genetic mutations having detrimental effects that are only felt late in life might persist in a population. Although widely accepted, this theory rests on the assumption that there is genetic variation for aging in natural systems, or (equivalently), that genotype-by-age interactions (GxA) occur for fitness. To date, empirical support for this assumption has come almost entirely from laboratory studies on invertebrate systems, most notably Drosophila and C. elegans, whereas tests of genetic variation for aging are largely lacking from natural populations. By using data from two wild mammal populations, we perform quantitative genetic analyses of fitness and provide the first evidence for a genetic basis of senescence to come from a study in the natural environment. We find evidence that genetic differences among individuals cause variation in their rates of aging and that additive genetic variance for fitness increases with age, as predicted by the evolutionary theory of senescence.
衰老，或称为老化，被定义为生理功能随年龄增长而下降，长期以来一直是进化生物学家研究兴趣的焦点。自然选择为何未能消除导致老年个体适应性降低的遗传效应？当前的进化理论通过表明，由于个体面临的环境致死风险，选择压力不可避免地随着年龄增长而减弱，来解释这一现象。这进而意味着那些仅在生命后期才显现出有害影响的基因突变可能会在种群中持续存在。尽管该理论被广泛接受，但它基于这样一个假设，即自然系统中存在衰老的遗传变异，或者（等效地），适应性存在基因型与年龄的相互作用（GxA）。迄今为止，对这一假设的实证支持几乎完全来自对无脊椎动物系统的实验室研究，最著名的是果蝇和秀丽隐杆线虫，而自然种群中衰老的遗传变异测试则基本缺失。通过使用来自两个野生哺乳动物种群的数据，我们对适应性进行了数量遗传学分析，并首次提供了在自然环境研究中衰老存在遗传基础的证据。我们发现证据表明个体之间的遗传差异导致了它们衰老速率的差异，并且如衰老的进化理论所预测的那样，适应性的加性遗传方差随着年龄增长而增加。
