基于叶绿体基因组探讨桃金娘目及其近缘类群的系统发育关系

Phylogeny of Myrtales and related groups based on chloroplast genome

该研究基于叶绿体基因组数据,对桃金娘目(6科44属97种)及其近缘类群(牻牛儿苗目2科5属25种)的系统发育关系进行了分析。结果表明:(1)桃金娘目基因组大小为152~171 kb,包括的蛋白质编码基因数目为74~90个;牻牛儿苗目基因组大小为116~242 kb,包括的蛋白质编码基因数目为75~132个。(2)对比叶绿体基因组序列和蛋白质编码基因所构建的系统发育树结果,在目间及牻牛儿苗目内差异显著,但在桃金娘目内基本一致。(3)基于蛋白质编码基因所构建的系统发育树表明,桃金娘目和牻牛儿苗目均为单系,为姐妹类群;桃金娘目内形成两个大支,桃金娘科、Vochysiaceae、野牡丹科形成一支,其中桃金娘科和Vochysiaceae关系较近是姐妹群,柳叶菜科、千屈菜科和使君子科形成另一支,其中柳叶菜科和千屈菜科关系较近为姐妹群;科级水平,桃金娘科、Vochysiaceae、野牡丹科、柳叶菜科、千屈菜科、使君子科和牻牛儿苗科均为单系(仅包括一个物种的科除外)。(4)支持将石榴属及菱属置于千屈菜科。(5)对蛋白质编码基因序列变异分析的结果表明,野牡丹科19个属的共享变异基因数目为53个,变异范围为5.84%~29.53%,桃金娘科9个属的共享变异基因数目为57个,其变异范围为1.31%~15.78%。该研究结果为进一步研究桃金娘目及相关科属的系统发育提供了理论依据。

In this study,we used the information on the chloroplast genomes to analyze the phylogenetic relationships of Myrtales(97 species representing 44 genera in six family)and related groups(Geraniales,25 species representing five genera in two families).The results were as follows:(1)The genome size of Myrtales ranged from 152 to 171 kb,including 74-90 protein-coding genes.The genome size of Geraniales ranged from 116 to 242 kb,including 75-132 protein-coding genes.(2)Phylogenetic analyses of whole genome and protein-coding genes yielded contradicting topologies for intra-order and Geraniales,but congruence results were found in Myrtales.(3)The phylogenetic tree based on protein-coding genes provided strong support for the monophyly of Myrtales and Geraniales and for the placement of Myrtales sister to the Geraniales;Within Myrtales,two major clades were identified,the first clade comprised a Melastomataceae lineage sister to a Myrtaceae+Vochysiaceae lineage and the second clade included Combretaceae sister to a subclade formed by the Onagraceae and Lythraceae lineages;At family level,Myrtaceae,Vochysiacea,Melastomataceae,Lythraceae,Onagraceae,Combretaceae and Geraniaceae were strongly supported as monophyletic(family that represented by only one species was excluded).(4)The placement of Punica and Trapa in Lythraceae were supported.(5)Additionally,the sequence divergence of the protein-coding genes was estimated.For Melastomataceae,53 variable protein-coding genes were identified,with the variation percentage ranged from 5.84%to 29.53%among the 19 genera.In Myrtaceae,the proportion of variability of 57 variable protein-coding genes ranged from 1.31%to 15.78%among the nine genera.Our study provides an important framework for further phylogenetic study in Myrtales and related groups.