Explaining responses to climate change in a wild vertebrate population

最近地球气候的变化与动植物种群的许多变化有关：例如，随着气温上升，许多物种的繁殖等关键事件的平均时间大大提前了。然而，我们对驱动这种气候变化反应的实际机制的了解仍然有限。重要的是，我们需要了解特定特征或特征（如时间、生长或繁殖力）发生变化的原因，这些变化决定了个体的适应性，从而决定了种群的总体增长率或下降率。随着时间的推移，人口特征的变化可能由以下三种不同过程中的一种或多种驱动：(i)不同年龄组代表的人口水平人口变化，每种变化可能表现出不同的特征值；（ii）个体水平的表型可塑性，即个体根据其所经历的环境条件表达不同的特征值；（iii）遗传水平的进化变化，即在新的环境条件下，种群的遗传组成因气候变化而发生变化，有利于不同的基因；随着时间的推移，这些对比机制都可以产生一个特征平均值的趋势，但它们对持续响应不断变化的环境，以及种群是否能够“跟上”气候变化有不同的含义。剖析它们的相对贡献需要详细的长期数据集。部分原因是，据我们所知，每种机制对观测到的气候变化反应的相对贡献的分析，尚未对任何野生动物种群进行量化。我们建议通过对苏格兰西北部朗姆酒岛上的马鹿（Cervus elaphus）野生种群的研究来解决这一差距。该项目将对4000多只单独监测的鹿近40年的数据进行分析。我们将首先探讨气候和/或植被变化对鹿性状的直接和间接影响；这将需要对植被特性的变化进行广泛的评估，为此我们将使用长期的地面和遥感数据。然后，我们的主要目标是量化上述三个过程对这些趋势的相对贡献。最后，我们将利用这些分析的见解来创建人口动态和个体特征的模型，从而产生对未来人口增长或下降速度的预测。朗姆酒马鹿项目可以说是这种分析的最佳数据资源。我们提出的新数据收集将提供研究期间植被特性变化的详细指示，以及不同年代的形态、繁殖成功、生存、时间特征和个体行为的足够数量的记录，以测试上述机制。我们的多代遗传验证谱系将使我们能够估计个体特征受遗传控制的程度，气候变化是否改变了这些特征的自然选择模式，以及种群是否对这种选择表现出进化反应。我们在分析所需的复杂统计和建模技术方面也有丰富的经验。我们的目标是提供迄今为止最全面的分析，分析野生动物种群如何应对气候变化，以及它们的自然变化能力是否有限。我们的研究将是同类研究中的首例。鉴于大型食草动物对生态系统功能的重要性，我们的研究结果将对未来的管理政策产生影响，并为气候变化影响野生种群的机制提供基本见解。

Recent changes in the earth's climate have been associated with numerous changes in animal and plant populations: for example, as temperatures have risen, the average timing of key events such as breeding has shifted substantially earlier in many species. However, we still have only limited knowledge of the actual mechanisms driving such responses to climate change. Importantly, we need to understand reasons for the changes that are occurring in the specific characteristics or traits (such as timing, growth or fecundity) that determine individuals' fitness and hence that shape a population's overall rate of growth or decline. Changes in a population's characteristics over time could be driven by one, or more, of three different processes:(i) population-level demographic changes in the representation of different age groups, each of which may display different trait values; (ii) individual-level phenotypic plasticity, whereby an individual expresses a different value of a trait dependent on the environmental conditions it experiences; (iii) genetic-level evolutionary change, whereby the genetic composition of the population changes in response to climate change favouring different genes under novel environmental conditions;These contrasting mechanisms can all generate a trend in the average value of a trait over time, but they have different implications for continued responses to a changing environment, and for whether or not a population can 'keep up' with climate change. Dissecting their relative contributions requires detailed, long-term data-sets. Partly because of this, this analysis of the relative contributions from each mechanism to observed responses to climate change have not yet, to our knowledge, been quantified for any wild animal population. We propose to address this gap using a study of a wild population of red deer (Cervus elaphus) on the Isle of Rum, NW Scotland.This project will enable an analysis of nearly four decades of data on more than 4000 individually-monitored deer. We will first explore the direct and indirect effects of climatic and/or vegetation variation on deer traits; this will require extensive assessments of changes in vegetation properties, for which we will use long-term ground-level and remote sensing data. Our primary aim is then to quantify the relative contributions of the three processes listed above to these trends. Finally, we will use insights from these analyses to create models of the dynamics of the population and of individual traits, and hence to generate predictions for future rates of population growth or decline.The Rum red deer project is arguably the best data resource anywhere for this analysis. The new data collection we propose will provide detailed indications of changes in vegetation properties over the study period, as well as sufficient numbers of records of the morphology, reproductive success, survival, timing characteristics and behaviour of individuals across different decades to test the mechanisms outlined above. Our multi-generation, genetically-validated pedigree will enable us to estimate the extent to which individual characteristics are under genetic control, whether climate change has altered patterns of natural selection on these characteristics, and whether the population has shown an evolutionary response to this selection. We also have extensive experience of the complex statistical and modelling techniques required for the analysis. Our ambition is to provide the most comprehensive analysis to date of how a wild animal population is responding to climate change and whether there are limits to its natural capacity to change. Our study will be the first of its kind. Given the importance of large herbivores to the way ecosystems function, our results will have implications for future management policy as well as offering fundamental insights into the mechanisms by which climate change affects wild populations.