How organisms adapt to the novel challenges imposed by the colonization of a new habitat has long been a central question in evolutionary biology. When multiple populations of the same species independently adapt to similar environmental challenges, the question becomes whether the populations have arrived at their adaptations through the same genetic mechanisms. In recent years, genetic techniques have been used to tackle these questions by investigating the genome‐level changes underlying local adaptation. Here, we present a genomic analysis of colonization of freshwater habitats by a primarily marine fish, the Gulf pipefish (Syngnathus scovelli). We sample pipefish from four geographically distinct freshwater locations and use double‐digest restriction site associated DNA sequencing to compare them to 12 previously studied saltwater populations. The two most geographically distant and isolated freshwater populations are the most genetically distinct, although demographic analysis suggests that these populations are experiencing ongoing migration with their saltwater neighbours. Additionally, outlier regions were found genome‐wide, showing parallelism across ecotype pairs. We conclude that these multiple freshwater colonizations involve similar genomic regions, despite the large geographical distances and different underlying mechanisms. These similar patterns are probably facilitated by the interacting effects of intrinsic barriers, gene flow among populations and ecological selection in the Gulf pipefish.

中文翻译：

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海湾pipe鱼重复淡水定居的种群基因组学

长期以来，生物如何适应新栖息地的殖民化所带来的新挑战一直是进化生物学的中心问题。当相同物种的多个种群独立适应相似的环境挑战时，问题就变成了这些种群是否通过相同的遗传机制达到了适应。近年来，遗传技术已用于通过研究局部适应的基因组水平变化来解决这些问题。在这里，我们介绍了主要由海水鱼类海湾pipe鱼（Syngnathus scovelli）对淡水生境定居的基因组分析。）。我们从四个地理上不同的淡水位置取样，并使用双消化限制性位点相关的DNA测序将它们与之前研究的12个咸水种群进行比较。地理上最遥远和最孤立的两个淡水种群在遗传上最不相同，尽管人口统计分析表明，这些种群正与咸水邻居一起持续迁移。此外，在全基因组范围内发现了异常区域，显示出各生态型对之间的平行性。我们得出的结论是，尽管地理距离遥远且潜在机制不同，但这些多个淡水定居涉及相似的基因组区域。内在障碍的相互作用可能会促进这些相似的模式，