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

尽管我们对进化是如何运作的有很好的总体理解，但我们对其在自然种群中的详细运作却知之甚少。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的进化变化。这一领域知识的改进将极大地促进我们对自然种群如何保持遗传多样性以及种群可能如何对气候预测变化做出反应的理解。种群中个体的特征是他们的基因、他们生活的环境以及到那时为止所发生的进化的结果。很多事情都很清楚，但这句简单的话隐藏了很多复杂的东西。具体地说，携带特定基因的后果可能会随着环境条件的不同而不同；生物体可能(但不是普遍证明)在良好的环境条件下表现出更多的遗传潜力。同样，自然选择的强度，即一些个体比其他个体具有更高的存活率或生殖成功率，可能会随着环境条件的不同而变化。由于进化变化发生在自然选择作用于遗传特征时，因此环境波动可能会对进化产生重大影响。最后，由于一个特定特征(如体型)的一些基因可能与另一个特征(如抗寄生虫)的基因相同或与之相关，因此特征不能自由地彼此独立进化。相反，自然选择对一个角色的影响将受到任何选择的限制，这些选择也发生在与它有基因联系的其他角色上。最近的研究表明，这些限制也随着环境条件的不同而不同。目前，我们对这些不同的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，我们将使用苏格兰西北部圣基尔达岛上一个未受管理的索伊绵羊研究种群的数据来研究环境条件对进化过程的影响。这个数据集对这项研究特别有用，因为首先，我们有数千只绵羊的个体生活史的记录，这些记录跨越了23年。DNA图谱已经被用来确定父子关系，并提供了适合于这里提出的那种遗传分析的家谱。其次，我们之前的研究表明，有四种环境变化对绵羊的生产性能表现出强烈的时间变化，本研究将研究这四种变化：天气、绵羊种群密度、食物可获得性和寄生虫丰度。我们将讨论上述环境条件对遗传变异表达的影响、自然选择的强度以及性状之间的遗传关系。具体地说，我们会问环境是如何影响的，首先是遗传变异在单个性状上的表现，比如体重：当条件好的时候，是否总是表现出更多的遗传变异？第二，环境变异是否会影响人物之间的遗传关系？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，选择是更强还是更弱？综合起来，这些分析将使我们能够预测特定时间序列环境条件下的演变过程--例如系统性气候变化。对这些单独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，拟议的拨款将保证英国最有价值的生态和进化野外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.