Life history and Ageing in the wild

研究为什么我们和所有其他生物随着年龄的增长而逐渐退化并变得更有可能死亡，这是一个与生物学中几乎所有其他问题相关的问题。然而，绝大多数的衰老研究都是关于机能衰退的机械论解释。首先，我们只是触及了衰老发生原因的功能性解释的皮毛，对于自然人口中老龄化是如何进行的，我们甚至更是一无所知。我们需要了解自然界中的衰老，因为很明显，自然界中衰老的作用方式将影响性别选择和生命历史进化等关键过程的动态。昆虫构成了动物生物多样性的绝大多数，并在实验室进行了深入的研究，它们已经成为了解衰老的重要模型系统。然而，当它们被带出一个食物无限、没有寄生虫或捕食者的环境时，昆虫很可能会表现出不同的衰老模式。现在很明显，即使是短命的昆虫也会在其自然寿命的时间尺度上经历衰老。昆虫作为了解衰老的实验室系统的重要性，以及开发可在野外和实验室研究的模型的潜力，使了解野生昆虫的衰老具有令人兴奋的前景。我们将通过非常详细的种群监测来研究野外蟋蟀自然种群的衰老。我们将对每个人进行DNA指纹和标记，然后使用160个摄像机组成的网络一天24小时观察他们。这将使我们不仅能够测量寿命和繁殖力，还可以收集详细的行为信息，使我们能够检测到在歌唱、在洞穴周围移动、在较长距离内移动、交配率、与其他个体打架成功等特征上可能非常微妙的下降。通过将我们在这个项目中收集的数据与我们在过去6-8年收集的数据结合起来，我们将解决一系列在野外很难回答的问题，因为其他研究没有我们拥有的详细信息：1.衰老的主要进化解释是，个体退化是因为他们在生命早期将所有能量投入繁殖，从而传递了更多的基因，即使这会在生命的后期造成损失。我们将确定在早期繁殖上投入更多精力的个体，例如通过交配更多的个体，最终是否会衰退得更快。我们将确定环境条件是否会影响个人衰老的速度，以及由于气候和个人之间的竞争而压力更大的年份是否与更快的衰老有关。3.据预测，雄性比雌性衰老得更快，因为它们的繁殖率不受产卵速度的限制；因此它们更有潜力进化，在早期繁殖上投入大量资金，即使这会杀死它们。我们将看看我们的男性是否比女性衰老得更快。雌性可能会从与老年雄性交配中受益，因为它们的后代从能够存活很长时间的雄性那里获得基因。如果基因好的男性比基因较差的男性衰老得慢，那么年龄增长将使女性选择年长的男性更加有利。我们将测试具有其他良好基因迹象的男性是否也会变老。有人提出，不同的死亡来源将对老龄化的演变产生不同的影响，这取决于条件较好的个人能否避免这些影响。我们将确定我们人口的死亡来源是否在这方面有所不同。例如，你是否被知更鸟吃掉可能仅仅是运气问题，而被另一只蟋蟀杀死可能取决于你有多大的能力来保护自己。

The study of why we, and all other living things, progressively deteriorate and become more likely to die as we get older is an issue of relevance to almost every other question in biology. However, the vast majority of ageing research is concerned with mechanistic explanations for declines in function. We have only really scratched the surface in terms of functional explanations for why ageing occurs in the first place, and we are even more in the dark in relation to how ageing proceeds in natural populations. We need to understand ageing in the wild, because it is clear that how ageing works in nature will affect the dynamics of key process such as sexual selection and the evolution of life-histories.Insects make up the vast majority of animal biodiversity and have been studied intensively in the lab, where they have become important model systems for understanding ageing. However, it seems very likely that when they are taken out of an environment where they have unlimited food and no parasites or predators, insects may show different patterns of senescence. It is now clear that even short lived insects experience senescence on the timescales of their natural life-spans. The importance of insects as laboratory systems for understanding ageing, and the potential for developing a model that can be studied in both field and lab makes understanding ageing in wild insects an exciting prospect. We will carry out a study of senescence in a natural population of field crickets by monitoring the population in great detail. We will DNA fingerprint and tag every individual, and then observe them 24 hrs a day using a network of 160 video cameras. This will enable us to not only measure lifespan and reproduction, but also to collect detailed behavioural information, allowing us to detect what may be quite subtle declines in performance in traits like singing, movement around their burrow, movement over longer distances, mating rate, success in fights with other individuals etc.By combining the data we will collect during this project with data we have collected over the previous 6-8 years, we will address a series of questions which have been very difficult to answer in the wild because other studies have not had the detailed information that we have:1. The main evolutionary explanation for ageing is that individuals deteriorate because they pass on more genes by putting all their energy into reproduction early in life even if this takes its toll later in life. We will determine whether individuals that put more effort into early reproduction, for instance by mating more, end up declining faster.2. We will determine whether environmental conditions affect how rapidly individuals age, and whether years which are more stressful due to climate and competition among individuals are associated with more rapid senescence. 3. Males have been predicted to age faster than females because their reproductive rate isn't capped by how fast they can lay eggs; so they have more potential to evolve to invest heavily in early reproduction even if it kills them. We will see if our males age faster than our females.4. Females may benefit from mating with old males because their offspring get genes from a male that was able to survive a long time. If males with good genes age slower than males with poorer genes then ageing will make female choice for old males even more beneficial. We will test whether males with other signs of good genes also age slower.5. It has been suggested that different sources of mortality will have different effects on the evolution of ageing depending on whether they can be avoided by individuals in better condition. We will determine whether the sources of mortality in our population vary in this respect. For instance, whether you get eaten by a robin may simply be a matter for luck, whereas being killed by another cricket may depend on how able you are to defend yourself.