Trans-generational costs of reproduction and the evolution of life histories

为什么种群中的某些个体随着年龄的增长比其他个体退化得更快？这是一个具有重要生物学和生物医学意义的问题，但仍然是一个谜。目前的理论是基于这样一种观点，即繁殖是昂贵的：在当前繁殖中投资更多的个体在未来繁殖成功率和生存率方面付出了代价。有很多证据支持这种繁殖成本，但潜在的机制仍然存在争议。一个主要的理论是，生殖需要增加氧化损伤的水平，这可能对细胞和组织的功能产生负面影响，从而降低生存率。然而，生殖增加氧化损伤的证据是模棱两可的：在某些情况下，繁殖个体显示出更高水平的氧化损伤，但越来越多的研究显示出相反的模式。我们最近提出，如果氧化损伤不仅对母亲有负面影响，而且对他们正在发育的后代也有负面影响，即如果存在跨代生殖成本，那么以前的结果可以解释。在这种情况下，母亲可以通过降低自身的氧化损伤水平来保护后代在敏感的发育窗口期免受伤害--“氧化屏蔽”假说（奥什）。氧化损伤的跨代影响可能对生长、繁殖和生存模式产生重大影响，但我们目前几乎没有理论来理解这些影响。我们的目标是发展这一新的跨代繁殖成本理论，并在一个易于处理的野生哺乳动物研究系统（带状猫鼬）中对奥什和我们的新模型进行首次测试。在自然种群中检验生命史理论特别有效，因为在自然种群中，权衡可以与它们对适应性的影响一起衡量。带状猫鼬是唯一适合我们的目标，因为我们知道所有动物的完整繁殖历史和血统，我们可以实验性地操纵母亲怀孕期间的营养状况，并跟踪他们的后代的发育和成功，因为他们长大了，开始繁殖自己。该项目将推进概念上的理解，为什么个体在发育和繁殖模式上差异如此之大，并帮助回答为什么有些人比其他人活得更久的问题。我们的理论框架可以很容易地应用于研究其他形式的损害，结转影响后代，如重金属中毒，或可传播的寄生虫和病原体。该项目完全符合NERC的战略优先事项，以管理环境变化和了解自然种群对环境危害的恢复力，因为这两个优先事项都需要更好地了解个人如何抵御环境挑战和压力源，以及一代人经历的扰动如何影响后代的生存能力。

Why do some individuals in a population deteriorate much more rapidly with age than others? This is a question of great biological and biomedical importance, but remains a puzzle. Current theory is based on the idea that reproduction is costly: individuals that invest more in current reproduction pay a cost in terms of reduced future reproductive success and survival. There is lots of evidence to support this proposed cost of reproduction, but the underlying mechanisms remain controversial. One major theory is that reproduction entails increased levels of oxidative damage, which can have negative consequences for the functioning of cells and tissues, and thereby reduce survival. However, evidence that reproduction increases oxidative damage is equivocal: in some contexts breeding individuals show higher levels of oxidative damage, but a growing number of studies show the opposite pattern.We recently suggested that previous results can be explained if oxidative damage has negative impacts not just on mothers, but also on their developing offspring, i.e. if there are trans-generational costs of reproduction. In these circumstances mothers could gain from reducing their own levels of oxidative damage to shield their offspring from harm during sensitive developmental windows - the 'oxidative shielding' hypothesis (OSH). Trans-generational impacts of oxidative damage could have a major impact on patterns of growth, reproduction, and survival, but we currently have almost no theory to understand these impacts. Our goal is to develop this new theory of trans-generational costs of reproduction, and to carry out the first test of the OSH and our new models in a tractable wild mammal study system, the banded mongoose. It is particularly powerful to test life history theory in natural populations, where trade-offs can be measured together with their consequences for fitness. The banded mongoose is uniquely suited to our objectives because we know the full breeding history and pedigree of all animals, and we can experimentally manipulate the nutritional condition of mothers during pregnancy and follow the development and success of their offspring as they grow up and start to breed themselves.The project will advance conceptual understanding of why individuals vary so much in patterns of development and reproduction, and help to answer the question of why some individuals survive longer than others. Our theoretical framework could readily be applied to study other forms of damage that carry-over to affect offspring, such as heavy metal poisoning, or transmissible parasites and pathogens. The project fits squarely with NERC's strategy priorities to manage environmental change and understand the resilience of natural populations to environmental hazards, because both of these priorities require improved understanding of how individuals defend against environmental challenges and stressors, and how perturbations experienced by one generation reverberate through to influence the viability of future generations.