Admixture in natural populations is a long‐standing management challenge, with population genomic approaches offering means for adjudication. We now more clearly understand the permeability of species boundaries and the potential of admixture for promoting adaptive evolution. These issues particularly resonate in western North America, where tectonism and aridity have fragmented and reshuffled rivers over millennia, in turn promoting reticulation among endemic fishes, a situation compounded by anthropogenic habitat modifications and non‐native introductions. The melding of historic and contemporary admixture has both confused and stymied management. We underscore this situation with a case study that quantifies basin‐wide admixture among a group of native and introduced fishes by employing double‐digest restriction site‐associated DNA (ddRAD) sequencing. Our approach: (a) quantifies the admixed history of 343 suckers (10 species of Catostomidae) across the Colorado River Basin; (b) gauges admixture within the context of phylogenetic distance and “ecological specialization”; and (c) extrapolates potential drivers of introgression across hybrid crosses that involve endemic as well as invasive species. Our study extends across an entire freshwater basin and expands previous studies more limited in scope both geographically and taxonomically. Our results detected admixture involving all 10 species, with habitat alterations not only accelerating the breakdown of reproductive isolation, but also promoting introgression. Hybridization occurred across the genus despite phylogenetic distance, whereas introgression was only detected within subgenera, implicating phylogenetic distance and/or ecological specialization as drivers of reproductive isolation. Understanding the extent of admixture and reproductive isolation across multiple species serves to disentangle their reticulate evolutionary histories and provides a broadscale perspective for basin‐wide conservation and management.

中文翻译：

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网状进化作为管理挑战：北美西部特有鱼类的系统发育距离混合模式。


自然种群的混合是一个长期存在的管理挑战，种群基因组方法提供了裁决手段。我们现在更清楚地了解物种边界的渗透性以及混合促进适应性进化的潜力。这些问题在北美西部尤其引起共鸣，数千年来，那里的构造运动和干旱使河流支离破碎和重新洗牌，进而促进了特有鱼类之间的网状分布，而人为栖息地改变和非本地引入使这种情况变得更加复杂。历史与现代的融合既混乱又阻碍了管理。我们通过一个案例研究强调了这种情况，该案例通过采用双消化限制性位点相关 DNA (ddRAD) 测序来量化一组本地和引进鱼类之间的流域范围内的混合。我们的方法：(a) 量化科罗拉多河流域 343 种吸盘虫（Catostomidae 的 10 种）的混合历史； (b) 在系统发育距离和“生态专业化”的背景下衡量混合； (c) 推断涉及特有物种和入侵物种的杂交杂交中基因渗入的潜在驱动因素。我们的研究涵盖了整个淡水流域，并扩展了先前在地理和分类学范围上更为有限的研究。我们的结果检测到涉及所有 10 个物种的混合物，栖息地的改变不仅加速了生殖隔离的崩溃，而且还促进了基因渗入。尽管存在系统发育距离，但杂交仍发生在整个属内，而基因渗入仅在亚属内检测到，这表明系统发育距离和/或生态专业化是生殖隔离的驱动因素。 了解多个物种之间的混合和生殖隔离程度有助于理清它们的网状进化历史，并为全流域的保护和管理提供广泛的视角。