Data from: Stream hierarchy defines riverscape genetics of a North American desert fish

Global climate change is apparent within the Arctic and the south-western deserts of North America, with record drought in the latter reflected within 640 000 km2 of the Colorado River Basin. To discern the manner by which natural and anthropogenic drivers have compressed Basin-wide fish biodiversity, and to establish a baseline for future climate effects, the Stream Hierarchy Model (SHM) was employed to juxtapose fluvial topography against molecular diversities of 1092 Bluehead Sucker (Catostomus discobolus). MtDNA revealed three geomorphically defined evolutionarily significant units (ESUs): Bonneville Basin, upper Little Colorado River and the remaining Colorado River Basin. Microsatellite analyses (16 loci) reinforced distinctiveness of the Bonneville Basin and upper Little Colorado River, but subdivided the Colorado River Basin into seven management units (MUs). One represents a cline of three admixed gene pools comprising the mainstem and its lower-gradient tributaries. Six others are not only distinct genetically but also demographically (i.e. migrants/generation <9.7%). Two of these (i.e. Grand Canyon and Canyon de Chelly) are defined by geomorphology, two others (i.e. Fremont-Muddy and San Raphael rivers) are isolated by sharp declivities as they drop precipitously from the west slope into the mainstem Colorado/Green rivers, another represents an isolated impoundment (i.e. Ringdahl Reservoir), while the last corresponds to a recognized subspecies (i.e. Zuni River, NM). Historical legacies of endemic fishes (ESUs) and their evolutionary potential (MUs) are clearly represented in our data, yet their arbiter will be the unrelenting natural and anthropogenic water depletions that will precipitate yet another conservation conflict within this unique but arid region.

全球气候变化已在北极地区与北美西南部沙漠地区显现，其中后者的创纪录干旱现象已波及64万平方公里的科罗拉多河流域范围。为厘清自然与人为驱动因素如何压缩了流域内鱼类生物多样性，并为未来气候变化影响评估建立基准基线，本研究采用河流层级模型（Stream Hierarchy Model, SHM），将河流地形特征与1092尾蓝头吸口鱼（Catostomus discobolus）的分子多样性进行对比分析。线粒体DNA（MtDNA）分析显示存在三个由地貌界定的进化显著单元（Evolutionarily Significant Unit, ESU）：邦纳维尔流域、小科罗拉多河上游河段以及其余科罗拉多河流域区域。微卫星标记分析（共16个基因座）进一步验证了邦纳维尔流域与小科罗拉多河上游河段的遗传独立性，同时将其余科罗拉多河流域划分为7个管理单元（Management Unit, MU）。其中一个单元包含由三个混合基因库构成的渐变群，覆盖干流及其低坡度支流。其余六个单元不仅遗传特征显著分化，种群结构亦彼此独立（即每代迁移个体占比<9.7%）。这六个单元中，两个单元（大峡谷与谢伊峡谷）由地貌特征界定；另外两个单元（弗里蒙特-穆迪河与圣拉斐尔河）因从西坡陡峭汇入科罗拉多河/格林河干流时存在急剧坡度而彼此隔离；另有一个单元为孤立的蓄水水体（林达尔水库）；最后一个单元对应已被认可的亚种（新墨西哥州祖尼河种群）。本研究数据清晰呈现了地方性鱼类进化显著单元的历史演化遗留特征及其管理单元层面的进化潜力，但其存续命运将取决于持续加剧的自然与人为水资源消耗——此类消耗将在这片独特却干旱的区域引发新一轮保护冲突。