The molecular basis of Mullerian mimicry

蝴蝶的拟态行为是进化和适应的一个范例，但其分子遗传学基础从未被研究过。在这里，我们将使用现代基因组技术，以确定基因控制的拟态模式属Heliconius，一个著名的进化模型系统。特别引人注目的是，我们最近发现三种Heliconius物种使用相同的遗传区域来控制颜色模式的变化。在两个物种中，H. melpomene和H.这些都是通过相互模仿进化而来的趋同模式。在第三种中，H. numata，模式是非常分歧和模仿物种从一个不同的亚科，Ithomiinae。此外，在H.该基因座是一个“超基因”，即一个单一的基因座，控制翅膀图案的所有方面，并在种群内是多态的（在同一种群中发现许多不同外观的形式一起飞行）。因此，基因组的同一区域以某种方式进化为控制收敛和发散模式。在这里，我们将使用H中已经开发的标记。melpomene来鉴定其他两个物种中的感兴趣区域，并获得足够大的区域的DNA序列，我们确信该区域包含所有三个物种中的感兴趣基因。这将允许在这三个物种之间的基因组组织在该区域的比较和基因组重组的测试，可能是翅膀图案的演变。特别是有一个长期存在的假设，即一个“超基因”，如在H。numata可能是通过逐渐将几个基因移到一起而产生的（这样做的进化优势是在野生种群中避免了不合适的中间模式）。这项研究将允许在分子水平上对这一假设进行首次明确的检验。然后，我们将确定该区域中的哪个位点控制H中的黄带模式。美波美我们将首先确定该区域中所有可能的基因作为图案化位点的候选者，并确定哪些基因在发育中的翅膀中表达，以及它们是否显示出与翅膀图案相关的任何图案。因此，我们的目标是确定Yb基因，控制一个带的后翅的H。melpomene，并比较三个物种之间的基因组在该基因座区域的组织。这项工作提供了一个不寻常的机会，将一个在自然种群中的重要性与DNA序列水平的变化联系起来。这将代表第一次在分子水平上表征了控制这种经过充分研究的性状的自然变异的基因，并将刺激未来Heliconius拟态的发育和群体遗传学研究。特别是，这些结果将有助于未来研究基因上的强选择如何影响周围基因组的变异。

Mimicry among butterfly species is a paradigm example of evolution and adaptation, but its molecular genetic basis has never been studied. Here we will use modern genomic techniques to identify genes controlling mimicry patterns in the genus Heliconius, a well-known evolutionary model system. What is particularly striking is our recent discovery that three Heliconius species use the same genetic region to control variation in colour patterns. In two of the species, H. melpomene and H. erato, these are convergent patterns that evolved through mutual mimicry. In the third species, H. numata, the patterns are very divergent and mimic species from a different sub-family, the Ithomiinae. Furthermore in H. numata the locus is a 'supergene' i.e. a single locus that controls all aspects of wing pattern and is polymorphic within populations (many different-looking forms are found flying together in the same population). Thus, the same region of the genome has somehow evolved to control both convergent and divergent patterns. Here we will use markers already developed in H. melpomene to identify the region of interest in the other two species and obtain DNA sequence for a sufficiently large region that we are sure contains the gene of interest in all three species. This will allow a comparison of genome organisation in this region between the three species and a test for reorganisation of the genome that may underlie the evolution of wing pattern. In particular there is a long-standing hypothesis that a 'supergene' such as that seen in H. numata might arise by gradually moving several genes together (the evolutionary advantage of this is that unfit intermediate patterns are avoided in wild populations). This study will allow the first explicit test of this hypothesis at a molecular level. We will then determine which locus in this region is controlling the yellow band pattern in H. melpomene. We will first identify all the possible genes in this region as candidates for being the patterning locus, and determine which ones are expressed in developing wings and whether they show any patterns that correlate with the wing patterns. We therefore aim to identify the Yb gene that controls a band on the hindwing of H. melpomene, and compare the organisation of the genome in the region of this locus between the three species. This work offers an unusual opportunity to link a trait whose importance in natural populations is well studied with a change at the level of DNA sequences. It will represent the first time that a gene controlling natural variation in such a well studied trait has been characterised at a molecular level, and will stimulate future developmental and population genetic studies of mimicry in Heliconius. In particular, the results will facilitate future studies of how strong selection on a gene affects variation in the surrounding genome.