Telomeres as biomarkers of cost and quality in a wild vertebrate population

因为资源和获得资源的时间是有限的，所以每个有机体都有有限的数量可以用来生存和繁殖。花在一个领域的资源，如卫生，不能花在另一个领域，如生殖。因此，有机体必须权衡如何最好地使用它们的资源，以使它们获得的利益最大化。这种权衡是我们理解不同生活史策略进化的核心，也就是为什么生物在大小、繁殖率和寿命等方面存在差异/这是生物学中的一个基本问题。问题是，尽管评估在一个领域投资对一个有机体的好处往往相对容易，但要理解权衡，我们还需要知道相关的成本。不幸的是，事实证明，衡量这样的成本是极其困难的，特别是在野生动物身上。此外，找出哪些机制将另类投资的成本联系起来，并在投资领域之间或一个有机体的整个生命周期内进行权衡，已经被证明超出了我们的能力范围。端粒是DNA的长而特殊的区域，它保护染色体的末端，防止细胞的基因在每次细胞复制时受到破坏或混合。然而，在每次复制过程中，端粒的一部分会丢失，当端粒达到关键的较短长度时，细胞就会停止工作。这些功能失调的细胞在人体组织中的积累被认为会导致衰老和衰老。重要的是，端粒缩短的速度也受到氧化应激/机体无法处理新陈代谢的破坏性废物(自由基)的很大影响。氧化应激(和/或端粒缩短)已被证明受到生活史和环境应激(如生长加速或感染)的影响。因此，端粒缩短可以表明这种压力对个体造成的生物学成本，并在这些成本与衰老和衰老之间提供了重要的联系。我们计划利用塞舌尔林莺独特的数据集，利用这个机会对野生脊椎动物种群中个体的端粒进行纵向研究。我们之所以能够做到这一点，是因为对该物种岛屿种群的长期密集研究意味着，可以获得关于所经历的环境因素和所作生殖投资的高度详细的信息。重要的是，每年的血液样本都是从许多已知年龄的人的一生中收集的。首先，我们将关注端粒缩短是否可以用来衡量野生种群的生物衰老。关键是确认与年龄相关的端粒长度可以预测塞舌尔林莺的寿命(和/或衰老)。然后，我们将通过将每年的端粒缩短率与他们在那一年所面临的压力联系起来，来调查不同压力的相对成本。实验操作将使我们能够专注于特定的因素，例如生殖努力。重要的是，成本将用通用货币单位(端粒缩短率)来衡量，这样不仅可以在压力之间进行比较，而且还可以与他们所经历的年龄和生活史阶段进行比较。这将使我们能够比较在不同的生活史组成部分或在应对环境压力方面的投资的成本和收益是如何权衡的。最后，我们将测试端粒缩短率的个体差异可以反映个体承受这些压力的能力，从而提供个体质量的指标的想法。

Because resources, and the time it take to acquire them, are limited, every organism has a finite amount it can use in its efforts to survive and reproduce. Resources spent on one area, such as health, cannot be spent on another, such as in reproduction. Consequently organisms must trade off how best to spend their resources so as to maximise the benefits they gain. Such trade-offs are central to our understanding of the evolution of different life-history strategies, i.e. why organisms differ in aspects such as their size, reproductive rate and lifespan / a fundamental question in biology. The problem is that, although it is often relatively easy to assess the benefit to an organism of investing in one area, to understand trade-offs we also need to know the associated cost. Unfortunately, measuring such costs has proved to be extremely difficult, especially in animals in the wild. Furthermore, working out which mechanisms link the costs of alternative investments, and mediate trade-offs between areas of investment, or across the lifetime of an organism, has proved beyond us. Telomeres are long, specialized regions of DNA that protect the ends of chromosomes and prevent the cells' genes from getting damaged or mixed up each time the cell replicates. However, a section of telomere is lost during each replication and when telomeres reach a critical, short length the cell stops functioning. The accumulation of these dysfunctional cells in the bodies' tissues is thought to lead to ageing and senescence. Importantly the rate at which telomeres shorten is also greatly affected by oxidative stress / the organism's inability to cope with the damaging waste products (free radicals) of metabolism. Oxidative stress (and/or telomere shortening) has been shown to be influenced by life history and environmental stresses (e.g. accelerated growth or infection). Telomere shortening can, therefore, indicate the biological cost that such stresses exact on an individual and provide an important link between these costs and ageing and senescence. We plan to use the unique dataset compiled on the Seychelles warblers to take the opportunity to undertake a longitudinal study of telomeres within individuals in a wild vertebrate population. We are only able to do this because the intensive long-term study of island populations of this species means that highly detailed information is available on the environmental factors experienced and reproductive investments made. Importantly, annual blood samples have been collected from many individuals of known age throughout their lives. First, we will focus on whether telomere shortening can be used as a measure of biological ageing in a wild population. Key to this is confirming that age-related lengths of an individual's telomeres predicts lifespan (and/or senescence) in the Seychelles warbler. We will then investigate the relative costs of different stresses by relating the annual telomere-shortening rate to the stresses they have faced in that year. Experimental manipulations will allow us to hone in on specific factors, such as reproductive effort. Importantly, costs will be measured with generic units of currency (telomere shortening rates) that would allow comparisons, not only between stresses, but also with respect to the age and life-history stage at which they are experienced. This will allow us to compare how the costs and benefits of investment in different life-history components, or in dealing with environmental stresses, are traded off. Finally, we will test the idea that individual variation in telomere shortening rate can reflect an individual's ability to withstand these stresses and, therefore, provide an indicator of individual quality.