Gunn Joe C, Berkman Leah K, Koppelman Jeff, Taylor Andrew T, Brewer Shannon K, Long James M, Eggert Lori S
Division of Biological Sciences University of Missouri Columbia Missouri USA.
Missouri Department of Conservation Columbia Missouri USA.
Ecol Evol. 2022 Oct 5;12(10):e9370. doi: 10.1002/ece3.9370. eCollection 2022 Oct.
The Neosho Bass (), a former subspecies of the keystone top-predator and globally popular Smallmouth Bass (), is endemic and narrowly restricted to small, clear streams of the Arkansas River Basin in the Central Interior Highlands (CIH) ecoregion, USA. Previous studies have detected some morphological, genetic, and genomic differentiation between the Neosho and Smallmouth Basses; however, the extent of neutral and adaptive divergence and patterns of intraspecific diversity are poorly understood. Furthermore, lineage diversification has likely been impacted by gene flow in some Neosho populations, which may be due to a combination of natural biogeographic processes and anthropogenic introductions. We assessed: (1) lineage divergence, (2) local directional selection (adaptive divergence), and (3) demographic history among Smallmouth Bass populations in the CIH using population genomic analyses of 50,828 single-nucleotide polymorphisms (SNPs) obtained through ddRAD-seq. Neosho and Smallmouth Bass formed monophyletic clades with 100% bootstrap support. We identified two major lineages within each species. We discovered six Neosho Bass populations (two nonadmixed and four admixed) and three nonadmixed Smallmouth Bass populations. We detected 29 SNPs putatively under directional selection in the Neosho range, suggesting populations may be locally adapted. Two populations were admixed via recent asymmetric secondary contact, perhaps after anthropogenic introduction. Two other populations were likely admixed via combinations of ancient and recent processes. These species comprise independently evolving lineages, some having experienced historical and natural admixture. These results may be critical for management of Neosho Bass as a distinct species and may aid in the conservation of other species with complex biogeographic histories.
尼奥肖小口黑鲈（）曾是关键顶级捕食者且全球广受欢迎的小口黑鲈（）的一个亚种，它是美国中部内陆高地（CIH）生态区阿肯色河流域小型清澈溪流特有的物种，分布范围狭窄。此前的研究已检测到尼奥肖小口黑鲈和小口黑鲈之间存在一些形态、遗传和基因组差异；然而，中性和适应性分化的程度以及种内多样性模式仍知之甚少。此外，一些尼奥肖种群的谱系多样化可能受到了基因流的影响，这可能是自然生物地理过程和人为引入共同作用的结果。我们使用通过ddRAD-seq获得的50,828个单核苷酸多态性（SNP）进行种群基因组分析，评估了CIH中小口黑鲈种群的：（1）谱系分化，（2）局部定向选择（适应性分化），以及（3）种群历史。尼奥肖小口黑鲈和小口黑鲈形成了具有100%自展支持的单系类群。我们在每个物种中鉴定出两个主要谱系。我们发现了六个尼奥肖小口黑鲈种群（两个非混合种群和四个混合种群）以及三个非混合的小口黑鲈种群。我们在尼奥肖小口黑鲈分布范围内检测到29个可能受到定向选择的SNP，这表明种群可能存在局部适应性。两个种群通过近期不对称的二次接触发生了混合，可能是在人为引入之后。另外两个种群可能是通过古代和近期过程的组合而混合的。这些物种包含独立进化的谱系，其中一些经历了历史上的自然混合。这些结果对于将尼奥肖小口黑鲈作为一个独特物种进行管理可能至关重要，并且可能有助于保护其他具有复杂生物地理历史的物种。
