Plastome-based phylogenomics resolves the placement of the sanguinolenta group in the spikemoss of lycophyte (Selaginellaceae)
Plastome-based phylogenomics resolves the placement of the sanguinolenta group in the spikemoss of lycophyte (Selaginellaceae)
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基于质体组的系统发育学解决了 sanguinolenta 类群在石松植物（卷柏科）穗苔中的位置
DOI：
10.1016/j.ympev.2020.106788
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发表时间：
2020
影响因子：
4.1
通讯作者：
Zhang Xian-Chun
中科院分区：
文献类型：
--
作者：
Zhang Hong-Rui;Wei Ran;Xiang Qiao-Ping;Zhang Xian-Chun
先前的研究已证明卷柏科是单系的，并且仅包括卷柏单一属。然而，该属的两个最新分类在所识别的亚属数量以及有问题的分支（例如“sanguinolenta”组）的位置方面存在分歧，这些分支在不同的研究中以完全不同的位置得到了解决。在这里，我们对卷柏科进行了基于质体基因组的系统发育分析来解决这个问题。此处由三个物种代表的 sanguinolentagroup 被确定为 Stachygynandrum 亚属其余成员的姐妹。此外，subg.Exaltatae、subg.Ericetorum 和 subg.Gymnogynumin clade A 聚类成一个得到良好支持的单系分支，但内部亚属之间的拓扑结构存在冲突，这可能归因于它们之间的早期分歧。我们发现卷柏科质体中同义（dS）和非同义（dN）取代率以及GC含量存在显着差异。 dS、dN和GC含量均显着高于其他石松植物（水松科和石松科）。我们观察到高 GC 含量与升高的 dS 和 dN 率之间存在显着的正相关性。此外，在卷柏科分支之间推断的 dS 和 dN 值变化很大。我们的数据表明，这种不均匀分布的替代率可能反映了不同谱系之间宽松或强化的选择，这可能与卷柏科亚属系统发育拓扑的不一致有关。
Selaginellaceae have been shown to be monophyletic in previous studies, and include only the single genusSelaginella. However, the two most recent classifications of the genus disagree in terms of the number of subgenera recognized, and the position of problematic clades such as the “sanguinolenta” group, which has been resolved in quite different positions in different studies. Here, we performed a plastid-genome based phylogenomic analysis of Selaginellaceae to address this problem. Thesanguinolentagroup, represented here by three species, was resolved as sister to the remaining members of subg.Stachygynandrum. Additionally, subg.Exaltatae, subg.Ericetorum, and subg.Gymnogynumin clade A clustered into a well supported monophyletic clade but with conflicting topology between subgenera inside, which is possibly attributed to the early divergence among them. We uncovered substantial variation in both synonymous (dS) and nonsynonymous (dN) substitution rate, and GC content in plastomes of Selaginellaceae. The values of dS, dN, and GC content were significantly higher than those of other lycophytes (Isoetaceae and Lycopodiaceae). We observed a significant positive correlation between the high GC content, and the elevated dSand dNrates. In addition, the dSand dNvalues inferred among branches of Selaginellaceae were extremely variable. Our data indicate that this unevenly distributed substitution rate likely reflected relaxed or intensified selection among different lineages, which is possibly related to the inconsistency of the subgeneric phylogenetic topologies of Selaginellaceae.