CEBC-CNRS UPR, 1934, F 79360 Villiers-en-Bois, France.
Ecology. 2013 Jan;94(1):208-20. doi: 10.1890/12-0215.1.
Theoretical and empirical studies have highlighted the effects of age on several life-history traits in wild populations. There is also increasing evidence for environmental effects on their demographic traits. However, quantifying how individuals differentially respond to environmental variations according to their age remains a challenge in ecology. In a population of Black-browed Albatrosses monitored during 43 years, we analyzed how life-history traits varied according to age, and whether individuals of different ages responded in different ways to environmental conditions. To do so, we: (1) examined how age affected seven life-history traits, (2) investigated differences in temporal variance of demographic traits between age classes, and (3) tested for age-dependent effects of climate and fisheries covariates on demographic traits. Overall, there was a tendency for traits to improve during the first years of life (5-10 years), to peak and remain stable at middle age (10-30 years), and decline at old ages. At young ages, survival and reproductive parameters increased, except offspring body condition at fledging, suggesting that younger parents had already acquired good foraging capacities. However, they suffered from inexperience in breeding as suggested by their higher breeding failures during incubation. There was evidence for reproductive and actuarial senescence. In particular, breeding success and offspring body condition declined abruptly, suggesting altered foraging capacities of old individuals. Middle-aged individuals had the lowest temporal variance of demographic traits. Although this is predicted by the theory of environmental canalization, it could also results from a higher susceptibility of young and old birds due to their respective inexperience and senescence. The highest temporal variances were found in old individuals. Survival was significantly influenced by sea surface temperatures in the foraging zone of this albatross population during breeding. During warm events survival of young and old individuals improved, whereas a decrease was observed for middle-aged individuals. Presumably, during cold years with poor environmental conditions, young and old breeding birds may suffer more from intraspecific competition for resources than middle-aged individuals. This study showed that age, known as a major factor structuring demography in long-lived species, can also potentially influence the response of populations to global change.
理论和实证研究强调了年龄对野生种群中几个生活史特征的影响。也有越来越多的证据表明环境对其人口特征有影响。然而，量化个体如何根据年龄对环境变化做出不同的反应仍然是生态学中的一个挑战。在一个被监测了 43 年的黑眉信天翁种群中，我们分析了生活史特征如何随年龄而变化，以及不同年龄的个体是否以不同的方式对环境条件做出反应。为此，我们：（1）研究了年龄如何影响七个生活史特征；（2）调查了不同年龄组之间人口特征时间方差的差异；（3）检验了气候和渔业协变量对人口特征的年龄依赖性影响。总的来说，生命史特征在生命的头几年（5-10 岁）有改善的趋势，在中年（10-30 岁）达到顶峰并保持稳定，在老年时下降。在年轻的时候，生存和繁殖参数增加，除了雏鸟出飞时的后代身体状况，这表明年轻的父母已经获得了良好的觅食能力。然而，由于在孵化期间的繁殖失败，他们在繁殖方面缺乏经验。有生殖和衰老的证据。特别是，繁殖成功率和后代身体状况急剧下降，表明老年个体的觅食能力发生了变化。中年个体的人口特征时间方差最低。尽管这是环境适应理论所预测的，但它也可能是由于年轻和老年鸟类各自的经验不足和衰老而导致的更高的敏感性。最高的时间方差出现在老年个体中。在繁殖期间，这种信天翁种群的觅食区海表温度显著影响了生存。在温暖的年份，年轻和老年个体的生存得到改善，而中年个体的生存则下降。据推测，在环境条件较差的寒冷年份，年轻和老年繁殖鸟类可能比中年个体更多地受到种内竞争资源的影响。本研究表明，年龄作为影响长寿物种种群结构的主要因素之一，也可能影响种群对全球变化的反应。
