Divergence and parallel evolution of boldness in guppies

动物行为变异的进化起源一直让生物学家既着迷又沮丧。尽管进行了数十年的研究，但我们仍然缺乏对某些机制的全面理解，这些机制有时会促进个体、种群和物种之间的变异，但也会限制多样性和限制分化。在这里，我们提出对来自特立尼达的一种小型淡水鱼孔雀鱼进行研究，以调查行为变异结构如何、何时以及为何在种群中发生变化。我们的研究是“比较的”——我们将调查多个野生种群的孔雀鱼在进化分歧中产生的行为变化模式。它也将是“多层次的”——我们试图理解种群之间的相似和差异模式，但是因为自然选择发生在种群内部的个体之间，为了实现这一点，需要研究个体和基因型之间的变异。两个已经分离的种群如何进化（“微观进化”）和分化（“宏观进化”）不仅取决于自然选择，还取决于遗传因素对个体之间行为差异的影响。此外，即使在没有自然选择的情况下，基因频率也会随着时间的推移而变化——那么，究竟有多少微观进化变化和宏观进化分歧是“中性”进化的结果呢？我们将重点关注“大胆”，这是行为的一个方面，可以被广泛理解为描述个人对环境中危险条件的反应。我们将研究的这组种群是在不同的捕食制度环境中进化的，这被认为是大胆选择的重要来源。我们将结合实验室中大规模的行为数据收集，操纵感知捕食风险的实验，以及统计遗传学和基因组学方法。比较已知进化关系（或“系统发育”）的种群之间的行为变异结构，将使我们能够有力地检验关于维持种群内的微小变异和驱动种群间差异的进化因素的假设。通过结合独特全面的基因组和行为数据，我们将测试种群之间的行为差异在多大程度上是由选择引起的，而不是在行为没有经过选择的情况下预期的潜在基因的“中性”进化。它们还将让我们探索行为变异的基因“构建块”，为基因型和行为之间的联系提供有价值的新见解。

The evolutionary origin of variation in animal behaviour continues to both fascinate and frustrate biologists. Despite decades of research, we still lack a comprehensive understanding of the mechanisms that sometimes promote variation among individuals, populations and species, but can also limit diversity and constrain divergence. Here we propose a study of guppies, a small freshwater fish from Trinidad, to investigate how, when and why the structure of behavioural variation changes across populations.Our study is 'comparative' - we will investigate patterns of behavioural variation arising from evolutionary divergence among multiple wild populations of guppies. It will also be 'multi-level' - we seek to understand patterns of similarity and difference among populations, but because natural selection happens among individuals within populations, to achieve this requires studying variation among individuals and genotypes. How two populations that have become separated evolve ('microevolution') and diverge ('macroevolution') does not only depend on natural selection, but also on the way in which genetic factors contribute to behavioural differences among individuals. Moreover, gene frequencies change over time even in the absence of natural selection - so just how much microevolutionary change and macroevolutionary divergence is the result of 'neutral' evolution?We will focus on 'boldness', an aspect of behaviour that can be broadly understood as describing an individual's response to risky conditions in the environment. The set of populations we will study have evolved in environments differing in predation regime, which is thought to be an important source of selection on boldness. We will combine large scale behavioural data collection in the laboratory, with experiments to manipulate perceived predation risk, and both statistical genetic and genomic methods. Comparing the structure of behavioural variation across populations of known evolutionary relationships to each other (or 'phylogeny') will allow us to robustly test hypotheses for the evolutionary factors maintaining shy-bold variation within populations, and driving differences among populations. By combining uniquely comprehensive genomic and behavioural data, we will test the extent to which differences in behaviour between populations arise from selection versus 'neutral' evolution of the underlying genetics that is expected even if behaviours are not under selection. They will also let us probe the genetic 'building blocks' of behavioural variation, providing valuable new insights into the links between genotype and behaviour.