Data from: Morphological and genetic analysis of sympatric dace within the Rhinichthys cataractae species complex: a case of isolation lost

AbstractThe Nooksack dace (Pisces: an undescribed putative taxon within Rhinichthys) and longnose dace (Rhinichthys cataractae) are two forms within the R. cataractae species complex that are distinguishable from one another by mitochondrial (mt) DNA divergence of 2–3%, as well as by subtle morphological differences. The two forms are found in allopatry in south-eastern British Columbia (BC), Canada, and adjacent areas of western Washington, USA, and are sympatric in three streams in the lower Fraser River valley, BC, and may represent cryptic species. We assayed 12 morphometric traits and two meristic characters (N = 582; 23 sampling locations) to test for diagnosability of the two dace, as well as to test for morphological differentiation by mtDNA type in sympatry. We then employed a 10-locus microsatellite DNA assay (N = 374; 12 sampling locations) to test for genetic distinction between Nooksack dace and longnose dace in sympatry. We found that the two dace could not be reliably differentiated morphologically: there was overlap in all characters measured, and sampling location had a much larger effect on morphology than mtDNA group. Microsatellite analysis showed no distinction by mtDNA type in localities with sympatric dace, indicating complete admixture between the sympatric Nooksack dace and longnose dace. The Nooksack dace and longnose dace provide an example of ‘ephemeral speciation’: two lineages that, despite an estimated 1.1 Myr of isolation, have developed no apparent barriers to reproduction and appear to have collapsed into a single interbreeding population where they come into secondary contact. Nonetheless, the zone of secondary contact and the diagnosability of the Nooksack dace in terms of mtDNA represent significant aspects of the evolutionary legacy within R. cataractae and support its conservation importance., Usage notesjruskey_usat-data_genepop-formatMicrosatellite DNA genotypes in base pairsjruskey&taylor_morphological-dataMorphological data for Ruskey and Taylor. All are in mm except two counts

摘要：努克萨克镖鱼（Nooksack dace，隶属于鱼纲（Pisces）鱥属（Rhinichthys），为一个尚未被正式描述的疑似类群）与长鼻镖鱼（Rhinichthys cataractae）均属于卡特拉鱥（R. cataractae）物种复合群内的两个类群，二者可通过2%~3%的线粒体（mt）DNA分化差异以及细微的形态差异加以区分。这两个类群在加拿大不列颠哥伦比亚省东南部及美国华盛顿州西部毗邻区域呈异域分布，而在加拿大不列颠哥伦比亚省弗雷泽河下游河谷的3条溪流中呈同域分布，二者可能代表隐存种。本研究测定了12项形态测量性状与2项可数性状（样本量N=582，覆盖23个采样点），以检验两种镖鱼的形态可鉴别性，同时验证同域分布类群中基于线粒体DNA类型的形态分化情况。随后，本研究采用10个位点的微卫星DNA检测方案（样本量N=374，覆盖12个采样点），检验同域分布的努克萨克镖鱼与长鼻镖鱼之间的遗传分化。研究结果显示，二者无法通过形态学手段可靠区分：所有测定性状均存在重叠，且采样地点对形态的影响远大于线粒体DNA类群的影响。微卫星分析结果表明，在同域分布的采样点中，未检测到基于线粒体DNA类型的遗传分化，说明同域分布的努克萨克镖鱼与长鼻镖鱼之间存在完全的基因混合。努克萨克镖鱼与长鼻镖鱼是"短暂成种（ephemeral speciation）"的典型案例：尽管两个支系的分化时间估计达110万年，但未形成明显的生殖隔离屏障，且在二次接触区域融合为一个随机交配的种群。尽管如此，二次接触区域以及基于线粒体DNA可鉴别的努克萨克镖鱼，仍是卡特拉鱥物种复合群演化历程中的重要特征，同时也凸显了其保护价值。使用说明：- jruskey_usat-data_genepop-format：碱基对形式的微卫星DNA基因型数据- jruskey&taylor_morphological-data：Ruskey与Taylor的形态学数据。除两项计数指标外，所有数据单位均为毫米（mm）。