The importance of gene flow in speciation of Heliconius

我建议使用现代高通量测序技术结合生态数据来解决物种形成研究中的一个主要问题：基因流在物种形成中的重要性。物种形成是新物种生物多样性产生的根本途径。然而，基因流在物种形成中的重要性，以及选择在这一过程中的作用还没有得到很好的理解。基因流动对物种形成有两种截然相反的影响：1）基因流动是物种形成的一个明显障碍，因为它往往会破坏共同适应的基因组合并使种群同质化。最近的理论论文概念化的进展，物种的分歧在一个四阶段模型的岛屿分歧海洋中的基因流。虽然很吸引人，但这种物种形成理论模型的经验支持仍然难以捉摸。2）在某些情况下，分类群之间的基因流动可能会在一个称为杂交物种形成的过程中引发新物种的形成。然而，杂交物种形成的令人信服的例子很少，特别是在动物之间。我将研究这两个影响的基因流对物种形成的Heliconius。新热带区Heliconius蝴蝶长期以来一直是研究物种形成的模型系统，因为存在代表整个物种形成连续体的分类群，从自由杂交的翅膀图案不同的种族，通过偶尔在自然界中杂交的同域物种，到完全生殖隔离的物种。随着第一个Heliconius基因组序列的公布，Heliconius现在提供了一个适合全面研究物种形成中基因流重要性的系统。elevatus，H. pardalinus和H.美波美我最近的工作已经证明了物种H之间的颜色模式基因的渐渗。melpomene和H.隆起的H. elevatus与H. pardalinus，但这两个是不同的物种，在很大程度上重叠的分布和已知的行为差异。初步数据表明，H. elevatus是杂种起源的，包括H. melpomene颜色模式基因嵌入H.帕达里努斯。收集全基因组序列数据，开展H. elevatus及其两个可能的亲本种，H. pardalinus和H.美波美这些数据将使我们能够测试假设的重要性和程度的基因流在物种形成。我有四个主要目标：1）我的分类单元采样将允许经验检验的岛屿的分歧假说的物种形成与基因流。2）我将遗传地图的特点负责的早期阶段的物种形成在H。elevatus和H. 3）实验设计将允许严格测试H. elevatus是杂交物种形成的结果。elevatus是由来自不同小种的单个或多个渐渗事件形成的。物种形成是一个基本的进化过程，塑造所有的生态系统，这项研究的结果将大大增加我们对新物种形成的基因组过程的理解。

I propose to use modern high-throughput sequencing technologies coupled with ecological data to address one of the major questions in speciation research: the importance of gene flow in speciation. Speciation is the fundamental route to the generation of new species biodiversity. However, the importance of gene flow in speciation, and the role of selection in this process are not well understood. Gene flow can have two diametrically opposite influences on speciation:1) Gene flow is an obvious hindrance to speciation as it will tend to break down co-adapted gene combinations and homogenize populations. Recent theoretical papers conceptualise the progress of species divergence in a four-phase model of islands of divergence amidst a sea of gene flow. While appealing, empirical support of this theoretical model of speciation remains elusive.2) In some cases gene flow between taxa could trigger the formation of new species in a process known as hybrid speciation. However, there are few convincing examples of hybrid speciation, particularly among animals.I will investigate these two effects of gene flow on speciation in Heliconius. Neotropical Heliconius butterflies have long been a model system for studying speciation owing to the the presence of taxa representing the entire speciation continuum from freely hybridizing races differing in wing patterning, through sympatric species that occasionally hybridize in nature, to fully reproductively isolated species. With the publication of the first Heliconius genome sequence, Heliconius now provides one of the few systems suited for comprehensively studying the importance of gene flow in speciation.The proposed research focuses on three Heliconius species: H. elevatus, H. pardalinus and H. melpomene. My recent work has demonstrated the introgression of colour pattern genes between the species H. melpomene and H. elevatus. H. elevatus is genetically very closely related to H. pardalinus, but the two are distinct species with largely overlapping distributions and known differences in behaviour. Preliminary data suggest that the genome of H. elevatus is of hybrid origin, comprising H. melpomene colour pattern genes embedded in a background of H. pardalinus. I will gather whole genome sequence data and carry out ecological field experiments on races of H. elevatus and its two putative parental species, H. pardalinus and H. melpomene. These resulting data will allow us to test hypotheses on the importance and extent of gene flow in speciation. I have four main objectives:1) My taxon sampling will allow empirical testing of the islands-of-divergence hypothesis of speciation with gene flow.2) I will genetically map traits responsible for the early stages of speciation in H. elevatus and H. pardalinus.3) The experimental design will allow rigorous testing of whether H. elevatus formed as a result of hybrid speciation.4) I will test whether H. elevatus was formed from a single or multiple introgression events from different races of H. melpomene.Speciation is a basic evolutionary process that shapes all ecosystems, and the findings of this research will add significantly to our understanding of the genomic processes underlying the formation of new species.