Data from: A new species of spottail darter endemic to the Clarks River in Kentucky and Tennessee (Percidae: Etheostomatinae: Etheostoma)

Etheostoma xanthovum, the Clarks Darter, is described as a new species endemic to the Clarks River in Kentucky and Tennessee, USA. Etheostoma xanthovum was previously delimited as Etheostoma oophylax, the Guardian Darter, based on morphological trait data. Subsequent to the description of E. oophylax, molecular phylogenetic analyses consistently resolved specimens from the Clarks River system and E. chienense, the Relict Darter, as sister species, which together formed a sister clade to all other sampled populations of E. oophylax. Our analyses of morphological traits, mitochondrial DNA (mtDNA), and genomic sampling using double digest restriction-site associated DNA (ddRAD) sequencing support the distinctiveness of Etheostoma xanthovum. Morphologically, Etheostoma xanthovum, differs from Etheostoma oophylax in the number of dorsal fin rays (12 versus 11), anal fin rays (8 versus 7), and in the number of scale rows around the caudal peduncle (21.8 versus 20.37). Etheostoma xanthovum does not share mtDNA haplotypes with Etheostoma oophylax or Etheostoma chienense. Phylogenomic analysis of an average of 28,448 ddRAD loci per sampled specimen resolves Etheostoma xanthovum and Etheostoma chienense as sister species, and assessment of genomic divergence supports the hypothesis that each of these two species represents a distinct and independently evolving lineage. In addition, we report a range extension of Etheostoma oophylax in the Obion River system, a direct tributary of the Mississippi River.

黄镖鲈（*Etheostoma xanthovum*，英文名Clarks Darter）是新描述的特有物种，仅分布于美国肯塔基州与田纳西州的克拉克河（Clarks River）流域。此前该物种曾被基于形态性状数据归入守护者镖鲈（*Etheostoma oophylax*，英文名Guardian Darter）。在守护者镖鲈被正式描述后，分子系统发育分析一致将克拉克河水系的标本与残遗镖鲈（*Etheostoma chienense*，英文名Relict Darter）鉴定为姊妹物种，二者共同构成了所有其他采样的*E. oophylax*种群的姊妹支系。本研究通过对形态性状、线粒体DNA（mitochondrial DNA, mtDNA）以及采用双酶切限制性位点相关DNA测序（double digest restriction-site associated DNA, ddRAD）获取的基因组样本进行分析，证实了黄镖鲈的物种独立性。形态学上，黄镖鲈与守护者镖鲈存在明显差异：背鳍鳍条数（12 vs 11）、臀鳍鳍条数（8 vs 7）以及尾柄周围鳞片行数（21.8 vs 20.37）均不相同。黄镖鲈与守护者镖鲈、残遗镖鲈均无共享的mtDNA单倍型。基于每个采样标本平均28448个ddRAD位点的系统基因组学分析，将黄镖鲈与残遗镖鲈明确为姊妹物种；基因组分化评估结果同样支持这两个物种均为独立演化谱系的假说。此外，本研究还报道了守护者镖鲈的分布范围扩展至密西西比河的直接支流奥比昂河（Obion River）水系。