The molecular causes of convergent evolution

1)大问题趋同进化是相似表型重复进化的自然实验，为进化过程提供了独特的见解。当相似的模式在不同的谱系中进化时，相同的分子机制在多大程度上被部署？相同的调控变化是否被增选为产生趋同表型？在快速进化过程中，单个基因座的进化变化如何调节复杂的模式变化？一种新的发育模式的进化所需要的精确的基因变化是什么？蝴蝶是一个很好的系统来解决这些问题。许多热带蝴蝶都有模仿翅膀的图案来警告捕食者它们的毒性，这已经成为了解趋同和多样化的分子基础，以及在野外自然选择和基因组进化之间建立联系的一个很好的系统。本文将研究热带蝴蝶模式收敛的分子基础。遗传作图和基因表达实验已经确定了一个由三个遗传位点组成的简单系统，该系统控制着海螺翅膀图案的复杂多样化。其中一个基因座调节黄色图案元素，而同样的基因座也与胡椒蛾、白桦和双环蝶的翅膀图案有关，这表明蝴蝶和蛾子有一个古老的共同图案系统。来自自然种群的表达模式和遗传数据表明，皮层是这个位点的功能基因，尽管表达数据也指出其他相关基因的参与。我们将应用最近开发的CRISPR/Cas9基因敲除方法来研究蝴蝶物种间模式趋同的分子基础。3)目标和预期结果我们将测试在模拟蝴蝶中进化的相似模式使用相同基因的频率。在更接近的解决方案中，我们还将测试当这些基因控制相似的模式时，它们是否受到相同的调节开关的控制，从而开启和关闭它们。这将测试在不同遗传背景下进化的可重复性。这些实验将涉及开发和应用新的基因编辑技术来研究这些蝴蝶的模式，这将为未来的进化研究设定标准。长期以来，人们一直认为这些蝴蝶的模仿模式是自然选择进化的典范，而这个项目将为在许多不同物种中产生如此惊人相似模式的分子机制提供独特的新见解。

1) The big questionsConvergent evolution is a natural experiment in repeated evolution of similar phenotypes, offering unique insights into the evolutionary process. When similar patterns evolve in different lineages, to what extent are the same molecular mechanisms deployed? Are the same regulatory changes co-opted into generating convergent phenotypes? How can evolutionary change at a single locus regulate complex patterning changes during rapid evolution? What are the precise genetic changes necessary for the evolution of a new developmental pattern? Heliconius butterflies are an excellent system to address these questions.2) The backgroundMany tropical butterflies have mimetic wing patterns to warn predators of their toxicity, and these have become an excellent system in which to understand the molecular basis for convergence and diversification, and make the link between natural selection in the wild and evolution in the genome. Here we will study the molecular basis for pattern convergence in tropical Heliconius butterflies. Genetic mapping and gene expression experiments have identified a simple system of three genetic loci that control the complex diversification in wing patterning seen in Heliconius. One of these loci regulates yellow pattern elements and the same genomic locus is also involved in wing patterning of both the peppered moth, Biston betularia, and the butterfly Bicyclus anynana, suggesting an ancient shared patterning system in butterflies and moths. Patterns of expression and genetic data from natural populations, suggest that cortex is the functional gene at this locus, although expression data also point to involvement of other linked genes. We will apply recently developed CRISPR/Cas9 methods for gene knockouts to investigate the molecular basis for pattern convergence between species of Heliconius butterflies. 3) Objectives and expected resultsWe will test the frequency with which similar patterns evolving in mimetic butterflies use the same genes. At a closer resolution, we will also test whether those genes are controlled by the same regulatory switches to turn them on and off, when they control similar patterns. This will test for the repeatability of evolution in different genetic backgrounds. These experiments will involve developing and applying novel gene editing techniques to study patterning in these butterflies, which will set the standard for evolutionary studies in the future. The remarkable patterns of mimicry in these butterflies have long been considered an exemplar of evolution by natural selection, and this project will offer unique new insights into the molecular mechanisms that produce such strikingly similar patterns in so many different species.