Genomics of incipient speciation in a highly vagile marine mammal: genome-wide analysis of demographic history, population structure and local adaptation in the endangered Galápagos sea lion

高度不稳定的海洋哺乳动物的早期物种形成的基因组学：对濒临灭绝的加拉帕戈斯海狮的人口历史、种群结构和局部适应进行全基因组分析

• 批准号: 255821879
• 负责人: Professor Dr. Joseph Hoffman
• 金额: --
• 依托单位: Institut für Bioinformatik und Systembiologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/255821879?language=en
• 关键词: Genomics; incipient; speciation; highly; vagile

One hundred and fifty years after Charles Darwins seminal work On the Origin of Species, the mechanisms by which animals speciate in the wild are still unresolved. However, the genomic revolution is now providing us with the necessary tools to investigate the genomic architecture of speciation. Among the most promising systems to reveal the evolutionary processes that control adaptation and govern the early steps of speciation are evolutionary young lineages diverging along strong environmental gradients. In particular, marine species provide ideal systems in which to test whether ecologically divergent selection in the absence of physical barriers to gene flow can lead to heterogeneous genomic divergence.The Galapagos sea lion (Zalophus wollebaeki) provides just such a system, occupying a remote, depauperate environment that has been a fertile ground for speciation research ever since the time of Charles Darwin. This species diverged from its Californian sister (Zalophus californianus) over one million years ago and has remained isolated ever since. Its range is tiny relative to the dispersal capability of the species but is characterized by a steep environmental cline between the nutrient rich grounds around the young western islands and the islands on the shallow central shelf of the archipelago. These environmental contrasts translate into marked differences in morphology, diet and the underlying genetics, as documented in a pilot study using 22 microsatellites and mitochondrial DNA. This challenges the view that geographic barriers to gene flow are required for genetic divergence and also makes the Galapagos sea lion a prime candidate for examining micro evolutionary processes that have facilitated local adaptation and localized genetic differentiation in the face of unrestricted dispersal potential.Our proposal will be among the first to harness the possibilities of the post genomic era in a unique ecological setting in the wild. We propose conducting genome-scale population genetic analyses across the entire species range, using the closely related Antarctic fur seal genome as a reference. The resulting data will allow us determine the primary mechanism underlying ecological incipient speciation, to identify speciation islands (i.e. candidate genomic regions carrying signatures of divergent selection) and to link these to divergent environmental parameters. These data will also provide an ideal opportunity to test the theoretical predication that the sex chromosomes speciate faster than the remainder of the genome. The combination of genome-scale population genetic approaches and coalescent modeling in this unique setting will yield fundamental insights into the evolutionary processes governing adaption and speciation in natural populations.

在查尔斯·达尔文的开创性著作《物种起源》出版150年后，动物在野外形成物种的机制仍然没有得到解决。然而，基因组革命现在为我们提供了必要的工具来研究物种形成的基因组结构。在揭示控制适应和支配物种形成早期步骤的进化过程方面，最有希望的系统是进化中的年轻谱系，它们沿着强烈的环境梯度发散。特别是，海洋物种提供了一个理想的系统，可以测试在没有物理障碍的情况下，生态上的差异选择是否会导致异质的基因组差异，加拉帕戈斯群岛的加拉帕戈斯海狮（Zalophus wollebaeki）就提供了这样一个系统，它占据了一个遥远的、贫瘠的环境，自查尔斯达尔文时代以来，这个环境一直是物种形成研究的肥沃土壤。这个物种在一百多万年前从它的加利福尼亚姐妹（Zalophus californianus）中分离出来，从此一直与世隔绝。它的范围相对于该物种的扩散能力来说很小，但其特点是在年轻的西部岛屿周围的营养丰富的理由和群岛的浅中央大陆架上的岛屿之间的陡峭的环境渐变。这些环境差异转化为形态，饮食和潜在遗传学的显着差异，正如使用22个微卫星和线粒体DNA的试点研究所记录的那样。这挑战了基因流的地理障碍是遗传分化所必需的观点，也使得加拉帕戈斯海狮成为研究微进化过程的主要候选人，这些微进化过程促进了当地的适应和本地化的遗传分化，面对不受限制的扩散潜力。我们的提议将是第一个利用后基因组时代在野外独特的生态环境中的可能性。我们建议在整个物种范围内进行基因组规模的群体遗传分析，使用密切相关的南极海狗基因组作为参考。 由此产生的数据将使我们能够确定生态初期物种形成的主要机制，以确定物种形成岛（即携带不同选择签名的候选基因组区域），并将其与不同的环境参数联系起来。这些数据也将提供一个理想的机会来测试性染色体比基因组的其余部分形成更快的理论预测。在这个独特的环境中，基因组规模的群体遗传方法和结合建模的结合将产生对自然群体中适应和物种形成的进化过程的基本见解。