质体系统发育基因组解析旋花科系统发育关系

Plastid phylogenomic insights into the phylogeny of Convolvulaceae

关键词:  旋花科, 系统发育关系, 质体基因组, 菟丝子属, 鱼黄草族

Key words:  Convolvulaceae, phylogenetic relationship, plastome, Cuscuta, Merremieae

摘要:

旋花科是一个世界广布的类群,具有丰富的形态特征和重要的经济价值。然而,目前该科主要分支或族间的系统发育关系问题一直未解决。为解析旋花科内系统发育关系,该研究代表性选取旋花科内8个族40个物种,基于质体全基因组数据,使用最大似然法和贝叶斯推论进行系统发育分析。结果表明:(1)旋花科质体基因组均为四分体结构,质体基因组大小为113 273～164 112 bp,蛋白质编码基因数目为66～79个。(2)基于五种DNA矩阵(即WCG、CDS、LSC、IR、SSC)的系统发育分析结果显示,WCG矩阵和CDS矩阵的拓扑结构基本一致,仅少数分支的支持率略有差异; LSC矩阵和WCG矩阵的拓扑结构差异在于菟丝子族、马蹄金族和盐帚花族的系统位置; AU检验和SH检验结果显示,WCG矩阵和SSC矩阵与IR矩阵的拓扑结构有显著冲突。(3)所有系统发育分析结果均显示,菟丝子属和马蹄金族都包括在旋花亚科内,应处理为族等级。(4)基于WCG矩阵和CDS矩阵较好地解决了旋花科8个族之间的系统发育关系,即心被藤族和丁公藤族聚为一支,最先从旋花亚科分化出来,随后是菟丝子族,剩下的5个族分成2个分支。(5)系统发育基因组分析证实,由于鱼黄草族特别是鱼黄草属是一个多系类群,因此需重新修订该族的分类地位和鱼黄草属的划分。

Abstract:

Convolvulaceae is a cosmopolitan family with rich morphological characteristics and important economic values. However, the phylogenetic relationships among the major branches or tribes in the family have not been fully resolved. In order to resolve these relationships, we sampled the complete plastome sequences from 40 species, representing eight tribes of Convolvulaceae, and reconstructed phylogenetic trees by using both maximum likelihood and Bayesian inference approaches. The results were as follows:(1)Convolvulaceae plastomes had the typical quadripartite structure, with the plastome size ranging from 113 273 to 164 112 bp and including 66-79 protein-coding genes.(2)Phylogenomic analyses using five DNA matrixes(i.e., WCG, CDS, LSC, IR, and SSC)showed that the topologies of the WCG and CDS trees were basically the same, with slight differences in support values for some branches. Topological differences were found between LSC and WCG topologies, especially for the positions of Cuscuteae, Dichondreae and Cresseae. The AU and SH tests showed that topological conflicts were significant between the WCG matrix and the SSC and IR matrixes.(3)All phylogenetic analyses confirmed that Cuscuta and Dichondreae were nested in Convolvuloideae and should be treated as tribes.(4)Phylogenetic relationships among the eight tribes were well resolved using the WCG and CDS matrixes: Cardiochlamyeae and Erycibeae formed a clade as the first divergent group of Convolvuloideae, followed by Cuscuteae, with the remaining five tribes forming two major clades.(5)The phylogenomic analyses confirmed that Merremieae were polyphyletic, especially Merremia, and that the circumscription and taxonomy of both Merremieae and Merremia will need revision.