Individual differences and the dynamics of animal populations

所有人口的规模每年都在波动。了解这些体型变化的原因对管理和保护种群很有帮助，三个多世纪以来生物学家一直对此感兴趣。直到最近，对种群规模变化的理解，即种群动态，都集中在调查数量的变化上，而忽略了个体之间的差异。在过去的几年里，人们越来越意识到，个体之间的年龄差异，以及体型或身体状况等特征的差异，对人类对环境变化的反应方式有着至关重要的影响。此外，生物学家已经认识到，进化变化的发生速度比以前所认识到的要快得多，而且生态和进化变化可以同时发生。这意味着理解种群动态的能力，是预测和管理种群所必需的，可能需要理解性状响应生态和进化压力的变化方式。因此，理解动力学可能需要深入了解生态和进化过程是如何联系在一起的。因为所有的生态和进化变化都是由个体群体之间的出生率和死亡率差异决定的，所以我们可以利用生活在一个种群中的个体的存活率和生育率数据，将性状分布的变化与种群规模的变化结合起来。这就是我们在这项拨款中要做的事情。我们所做的工作将带来什么？举个具体的例子：从种群中收获大型个体不仅会影响成年个体的数量，还会改变动物争夺资源的方式，让较小的个体有更多的机会，也许会让它们生长或繁殖更多；这也可能改变平均繁殖率，因为体型较大的个体可能繁殖更多，或者产生更高质量的后代。收获也将改变个体的选择压力，使其更有利于早熟和小尺寸。因此，收获的影响比简单地移除一些个体而其他个体保持不变要深远得多。我们希望我们的工作能够让我们理解(1)有选择地从种群中移除特定的个体可能会影响种群的动态，以及(2)不同类型的环境如何导致体型等特征分布的变化。这将提供一些信息，告诉我们气候变化如何影响体型等特征的进化，以及种群规模的波动。我们将采用的方法从未应用于动物。我们将使用四种截然不同的动物物种的数据：一种是一夫一妻制的鸟，银眼鸟；自由生活的沙伊羊；群居的猫鼬;以及实验室土壤螨的种群。之所以选择这些系统，是因为以前的研究已经对其生态的许多方面提供了很好的理解，因为有详细的数据，因为它们有非常不同的生活史和生态。通过同时对一系列物种进行研究，我们还能够对结论的普遍性有一种感觉，以及我们需要在多大程度上发展对数量和特征变化方式的共同理解。

All population fluctuate in size from year to year. An understanding of the causes of these changes in size is helpful when managing and conserving populations and has interested biologists for more than three centuries. Until recently, understanding changes in population size, i.e. population dynamics, has concentrated on investigating the changes in numbers alone, ignoring differences between individuals. Over the last few years there has been an increasing realisation that differences between individuals in age but also in traits like body size or condition crucially affect the way populations respond to changes in the environment over time. In addition, biologists have realised that evolutionary change can happen much faster than had previously been appreciated and that ecological and evolutionary change can happen simultaneously. This means that an ability to understand population dynamics, necessary to predict and manage populations, may require understanding of the way traits change in response to ecological and evolutionary pressures. Understanding dynamics may therefore require insight into how ecological and evolutionary processes are linked. Because all ecological and evolutionary change is determined by differences in birth and death rates between groups of individuals, we can use data on the survival and fertility rates of individuals living within a population to marry changes in trait distributions to changes in population size. This is what we will do in this grant. What will the work we do deliver? Take a concrete example: harvesting large individuals from a population will affect more than just the numbers of adults: it will alter the way the animals compete for resources, allowing smaller individuals greater access, perhaps allowing them to grow or reproduce more; it is also likely to alter average reproductive rates as larger individuals may reproduce more, or give rise to higher quality offspring. Harvesting will also alter the selection pressure on individuals, making it more beneficial to mature earlier and at a smaller size. Thus harvesting's effects are more profound than simply the removal of some individuals leaving all others unchanged. We expect that our work will allow us to understand how (1) selectively removing specific individuals from a population is likely to impact the dynamics of the population, and (2) how different types environments lead to changes in the distribution of traits like body size. This will provide some information on how we might expect changes in the climate to influence both the evolution of traits like body size, as well as fluctuations in population size. The approach we will take has never been applied to animals. We will use data from four contrasting animal species / a monogamous bird, the silvereye; free-living Soay sheep; group-living meerkats; and laboratory populations of soil mites. These systems have been chosen because previous research has provided a good understanding of many aspects of their ecology, because detailed data exist and because they have very different life histories and ecologies. By investing a range of species simultaneously, we will also be able to get a feeling for the generality of our conclusions and the degree to which we need to develop joint understanding of the way numbers and traits vary.