The ecology of evolution: the role of environmental heterogeneity in evolutionary dynamics.

虽然我们对进化如何运作有了很好的一般性理解，但我们对自然种群中的详细运作只有有限的了解。一个突出的挑战是了解环境条件的变化在多大程度上影响自然种群内的进化变化。这一领域知识的提高将极大地促进我们对自然种群遗传多样性如何维持以及种群如何可能对预测的气候变化作出反应的理解。群体中个体的特征是其基因、生活环境和迄今为止发生的进化的结果。这么多是清楚的，但这个简单的声明隐藏了很多复杂性。具体来说，携带特定基因的后果可能会因环境条件而异;生物体在良好而不是恶劣的环境条件下表达更多的遗传潜力是可能的（但通常没有得到证明）。同样，自然选择的力量，即某些个体比其他个体具有更高的生存或繁殖成功率，可能会因环境条件而异。由于当自然选择作用于遗传特征时，进化就会发生变化，因此环境波动会对进化产生重大影响。最后，由于某些构成特定性状（如体型）的基因可能与构成另一性状（如抗寄生虫性）的基因相同或相关，因此性状不能独立地自由进化。相反，自然选择对一个性状的影响将受到任何选择的限制，这些选择也发生在与它有遗传联系的其他性状上。最近的研究表明，这些限制也随环境条件而变化。目前，我们对这些不同过程如何相互作用以塑造自然种群的进化知之甚少。在这项研究中，我们将调查环境条件对进化过程的影响，使用的数据从一个未管理的研究人口的Soay羊的圣基尔达岛，苏格兰西北部。该数据集对这项研究特别有用，因为首先，我们记录了23年来测量的数千只绵羊的个体生活史。DNA分析已被用来确定亲子关系，并提供了一个适合这里提出的遗传分析的家谱。其次，我们以前的研究表明，有四种环境变化，表现出强烈的时间变化影响绵羊的生产性能，我们将在这项研究中调查所有四种变化：天气，绵羊种群密度，食物供应和寄生虫丰度。我们将讨论上述环境条件对遗传变异的表达、自然选择的强度和性状之间的遗传关系的影响。具体来说，我们首先要问环境是如何影响的，遗传变异在单个性状（如体重）中的表达：在条件好的情况下，是否总是表达更多的遗传变异？第二，环境变化是否影响性状间的遗传关系？例如，在好的或坏的条件下，身体大小和寄生虫的抵抗力是否更容易单独进化？第三，在良好的环境条件下，选择是强还是弱？这些分析将使我们能够预测特定时间序列的环境条件下的进化过程-例如系统的气候变化。对这些个体识别的野生动物的长期研究是生态学和进化生物学许多方面的重要信息来源，拟议的赠款将保证英国最有价值的生态和进化领域数据集之一的数据收集的连续性。

Although we have a good general understanding of how evolution operates, we have only limited insight into its detailed workings in natural populations. A prominent challenge is to understand the extent to which variation in environmental conditions affects evolutionary change within natural populations. Improved knowledge in this area will greatly advance our understanding of how genetic diversity is maintained in natural populations and of how populations are likely to respond to predicted changes in climate. The characteristics of individuals in a population are a consequence of their genes, the environment in which they live and the evolution that has occurred up to that point. So much is clear, but this simple statement conceals much complexity. Specifically, the consequences of carrying particular genes can vary with environmental conditions; it is possible (but not generally proven) that organisms express more of their genetic potential under good rather than bad environmental conditions. Similarly, the strength of natural selection, whereby some individuals have higher survival or reproductive success than others, may vary with environmental conditions. Since evolutionary change occurs when natural selection acts on inherited characters, environmental fluctuations can therefore have a substantial impact on evolution. Finally, because some of the genes underlying a particular character (e.g. body size) may be the same as, or associated with, the genes underlying another character (e.g. parasite resistance), characters are not free to evolve independently of one another. Instead the effect of natural selection on one character will be constrained by any selection that is also occurring on other characters to which it is genetically tied. Recent research suggests that these constraints also vary with environmental conditions. Currently, we have very little understanding of how these various processes interact to shape evolution in natural populations. In this study we will investigate the effect of environmental conditions on evolutionary processes using data from an unmanaged study population of Soay sheep on the island of St Kilda, NW Scotland. The data set is particularly useful for this study because, firstly, we have records on the individual life histories of several thousand sheep measured across 23 years. DNA profiling has been used to determine paternity and provide a family tree suitable for the kind of genetic analyses proposed here. Secondly, our previous research has demonstrated that there are four kinds environmental variation which show strong temporal variation affecting sheep performance, and we will be investigating all four kinds of variation in this study: the weather, sheep population density, food availability and parasite abundance. We will address the effect of the environmental conditions described above on the expression of genetic variation, the strength of natural selection and the genetic relationships between characters. Specifically we will ask how the environmental affects first, the expression of genetic variation in single characters like body weight: is more genetic variation always expressed when conditions are good? Second does environmental variation affect genetic relationships between characters? For example, are body size and parasite resistance freer to evolve separately under good or bad conditions? Third, is selection stronger or weaker under good environmental conditions? Together these analyses will allow us to predict the course of evolution under specific time series of environmental conditions - for example systematic climate change. Long-term studies of individually-recognised wild animals such as these are an important source of information on many aspects of ecology and evolutionary biology, and the proposed grant would guarantee continuity of data collection for one of the UK's most valuable ecological and evolutionary field data sets.