Effects of early and adult environment conditions on the biology of long-lived species: testing the "predictive adaptive response" hypothesis

了解是什么使一些个体更容易受到恶劣环境条件的影响或更具弹性，这是生物学中的主要兴趣。人们越来越认识到，生命早期遇到的环境条件，包括母亲的影响，可能会对成年后的不同特征产生长期影响，包括形态、生殖、生理和新陈代谢(Bateson等人，2014年；Lemaitre等人，2015年)。然而，不同的理论对长期影响做出了相互矛盾的预测。一方面，生活史理论预测了早年和晚年之间的权衡(Lemaitre等人，2015年)。因此，它预测，与成人环境无关，在恶劣环境条件下出生的个体将比在最好条件下出生的个体具有更低的繁殖力和更快的衰老。另一方面，代谢编程假说认为，成长中的个体调整他们的生理和新陈代谢，以适应他们在成年期可能接触到的条件(Bateson等人，2014)。因此，它预测，与在最好的条件下出生的人相比，在恶劣条件下出生的人在成年后应该更好地适应恶劣条件。虽然这两个假设都得到了一些支持，但它们并没有在一个综合框架中同时得到解决。这一博士项目将利用美国科罗拉多州黄腹土拨鼠自然种群的多世代数据集，来测试早期和成年环境条件如何相互作用并影响生殖、生存和生理。在同一个体生命周期中收集的新的和存档的样本将被用来测试候选代谢过程在塑造对环境的适应方面的贡献。具体地说，分析将测试早期和成年条件对代谢(瘦素、T3、T4、胰岛素样激素)和应激(皮质醇)激素循环水平变化的影响。由于冬眠，黄腹旱獭的活动季节减少到五个月，在此期间个体繁殖和积累脂肪储备以度过冬天，这意味着春季和夏季的天气条件对包括幼崽和一岁以下的发育、成体繁殖和生存在内的所有生命阶段都有很大的影响(Martin等人，2014年)。自1965年以来收集了有关生长、存活和繁殖的信息，自2002年以来收集了生物样本。在过去的二十年里，环境条件有很大的不同，因此这个系统提供了一个独特的机会来测试早期和成年环境条件对长寿有机体生物学的影响。

Understanding what makes some individuals more susceptible or more resilient to harsh environmental conditions is of major interest in biology. There is growing appreciation that environmental conditions encountered early in life, including maternal effects, can have long-lasting effects on different traits in adulthood including morphology, reproduction, physiology and metabolism (Bateson et al 2014; Lemaitre et al 2015). However, different theories make contradicting predictions about the long-lasting effects. On one hand, life-history theory predicts a trade-off between early and late life (Lemaitre et al 2015). It thus predicts that, independently of the adult environment, an individual born in harsh environmental conditions will have lower reproduction and senesce faster than an individual born under prime conditions. On the other hand, the metabolic programming hypothesis considers that growing individuals adjust their physiology and metabolism to conditions they may become exposed to during adulthood (Bateson et al 2014). Thus, it predicts that individuals born under harsh conditions should be better adapted at adulthood to resist harsh conditions when compared to individuals born under prime conditions. Although both hypotheses received some support, they have not been addressed at the same time in an integrative framework. This PhD project will exploit a multi-generation dataset from a natural population of yellow-bellied marmots in Colorado, USA, to test how early and adult environmental conditions interact and influence reproduction, survival and physiology. New and archived samples collected on the same individuals during its life course will be used to test the contribution of candidate metabolic processes in shaping adaptation to the environment. Specifically, analyses will test for effects of early and adult conditions on changes in circulating levels of metabolic (leptin, T3, T4, insulin-like hormone) and stress (cortisol) hormones. Due to hibernation, the yellow-bellied marmot active season is reduced to five months in which individuals reproduce and accumulate fat reserves to survive the winter implying that spring and summer weather conditions have strong effect on all life stages including pups and yearling development, adult reproduction and survival (Martin et al 2014). Information on growth, survival and reproduction have been collected since 1965 and biological samples since 2002. The last two decades have been marked by much contrasted environmental conditions, and hence this system offers a unique opportunity to test for effects of early and adult environmental conditions on the biology of a long-lived organism.