Gut microbiome variation, fitness and senescence within a natural vertebrate population

很明显，许多动物种群在繁殖成功、存活和衰老(衰老)方面存在广泛的个体差异，但导致这种差异的原因在很大程度上仍不清楚。了解这种变异的驱动因素非常重要，这既是因为差异适应度是适应性进化的基础，也是因为这种理解可能有助于改善个体的健康和福祉。对人类和圈养动物的研究表明，肠道微生物群(GM)的组成变化可以在宿主功能中发挥重要作用，影响消化、免疫和发育等组成部分，并影响有害条件和疾病的结果。研究还表明，GM的变化可以在个体随年龄增长而恶化的过程中起到因果作用。因此，鉴于转基因似乎对宿主的健康是不可或缺的，我们可以假设转基因的变异将对个体的生存和繁殖成功产生重要影响。基因变异也可能导致在人群中观察到的个体之间的广泛的、基本上无法解释的衰老差异，包括在人类中。因此，令人惊讶的是，对于确定自然种群内个体之间存在多少转基因变异，或者是哪些因素推动了这种变异，所做的工作如此之少。更重要的是，据我们所知，还没有研究确定个体转基因变异是否与野生脊椎动物种群的繁殖成功和衰老有关。鉴于非自然条件可以从根本上改变个体的转基因，而个体与其环境之间的复杂相互作用影响着生存和繁殖成功，如果我们要充分了解转基因变异的原因和适应结果，自然条件下的研究是必不可少的。我们的目标是通过全面调查细菌转基因个体变异的原因来填补我们知识中的空白，并首次研究这如何与自然脊椎动物种群的适应性和衰老有关。我们完全有条件这样做，因为我们对塞舌尔林莺离散种群的长期研究，使我们能够在它们的一生中跟踪和采样它们。我们有详细的环境、遗传、生物条件和准确的生存和繁殖成功数据(不受扩散的影响)。我们还拥有10代人的遗传谱系，结合不同的社会亲子关系模式(例如，由于不忠)，为强有力地分析转基因特征的遗传性提供了基础。重要的是，我们由NERC资助的初步研究成功地测试了粪便样本中转基因变异的测序和分析方案，我们的结果证实了该人群中存在相当大的转基因个体变异。我们现在已经准备好了一切，以促进这项新颖而及时的研究的成功。证实野生种群中存在的自然共变是揭示转基因进化重要性的关键一步。这一建议将使我们能够确定自然选择所需的组成部分--个体变异、与该变异相关的差异适应度以及该变异的遗传--是否存在于自然种群中的转基因。这些证据将第一次为脊椎动物宿主的自然选择是由转基因基因介导的观点提供强有力的支持。从应用的角度来看，了解转基因变异的原因和后果也很重要，因为它将告诉我们如何管理转基因多样性，以优化我们自己的健康，以及我们利用或希望保护的动物的特征和状况。

That extensive individual variation in reproductive success, survival and senescence (ageing) exists in many animal population is clear, however what causes this variation remains largely unexplained. Understanding the drivers of this variation is of great importance, both because differential fitness is the basis of adaptive evolution, but also because such understanding may help improve the health and wellbeing of individuals.Studies on humans and captive animals have shown that variation in the composition of the gut microbiome (GM) - a complex microbial community comprising thousands of species - can play an important role in host function, influencing components such as digestion, immunity and development, and affecting the outcome of deleterious conditions and disease. Research has also suggested that changes in the GM can play a causal role in an individual's deterioration with age. Therefore, given that the GM appears to be integral to the health of its host, we can hypothesise that variation in the GM will have important consequences for an individual's survival and reproductive success. GM variation may also contribute to the extensive, and largely unexplained, differences in senescence observed among individuals within populations, including in humans. It is then surprising that so little work has been undertaken to determine how much GM variation exists among individuals within natural populations, or which factors drive this variation. More importantly, to our knowledge no studies have yet determined if individual GM variation is associated with reproductive success and senescence within a wild vertebrate population. Given that unnatural conditions can radically change an individual's GM, and complex interactions between the individual and its environment influence survival and reproductive success, studies under natural conditions are essential if we are to fully understand the causes and fitness consequences of GM variation.We aim to fill these gaps in our knowledge by undertaking a comprehensive investigation of the causes of individual variation in the bacterial GM, and, for the first time, how this is linked to fitness and senescence within a natural vertebrate population. We are perfectly placed to do this because our long-term study of a discrete population of the Seychelles warbler Acrocephalus sechellensis, allows us to follow and sample individuals throughout their lives. We have detailed environmental, genetic, biological condition and accurate survival and reproductive success data (unconfounded by dispersal) on individuals across their lives. We also have a 10-generation genetic pedigree of the population which, combined with contrasting patterns of social parentage (e.g. due to infidelity), provides the basis for a powerful analysis of the heritability of GM characteristics. Importantly, our NERC-funded pilot study successfully tested protocols for the sequencing and analysis of GM variation from faecal samples, and our results confirm that considerable individual variation in the GM exists within this population. We now have everything in place to facilitate the success of this novel and timely study.Assessing the natural co-variation that exists in a wild population is an essential step in exposing the evolutionary importance of the GM. This proposal will allow us to determine if the components required for natural selection - individual variation, differential fitness linked to that variation, and inheritance of that variation - exist in terms of the GM within a natural population. Such evidence would, for the first time, provide strong support for the idea that natural selection on vertebrate hosts is mediated by the GM. Knowledge of the causes and consequences of GM variation is also important from an applied perspective as it will inform how we can manage GM diversity to optimise our own health, and the traits and condition of the animals that we utilise or wish to conserve.