单子叶植物高级分类阶元系统演化:matK、rbcL和18S rDNA序列的证据

The higher-level phylogeny of monocots based on matK, rbcL and 18S rDNA sequences

基于两个叶绿体基因(matK和rbcL)和一个核糖体基因(18S rDNA)的序列分析,对代表了基部被子植物和单子叶植物主要谱系分支的86科126属151种被子植物(单子叶植物58科86属101种)进行了系统演化关系分析。研究结果表明由胡椒目Piperales、樟目Laurales、木兰目Magnoliales和林仙目Canellales构成的真木兰类复合群是单子叶植物的姐妹群。单子叶植物的单系性在3个序列联合分析中得到98%的强烈自展支持。联合分析鉴定出9个单子叶植物主要谱系(广义泽泻目Alismatales、薯蓣目Dioscoreales、露兜树目Pandanales、天门冬目Asparagales、百合目Liliales、棕榈目Arecales、禾本目Poales、姜目Zingiberales、鸭跖草目Commelinales)和6个其他被子植物主要谱系(睡莲目Nymphaeales、真双子叶植物、木兰目、樟目、胡椒目、林仙目)。在单子叶植物内,菖蒲目Acorales(菖蒲属Acorus)是单子叶植物最早分化的一个谱系,广义泽泻目(包括天南星科Araceae和岩菖蒲科Tofieldiaceae)紧随其后分化出来,二者依次和其余单子叶植物类群构成姐妹群关系。无叶莲科Petrosaviaceae紧随广义的泽泻目之后分化出来,无叶莲科和剩余的单子叶植物类群形成姐妹群关系,并得到了较高的支持率。继无叶莲科之后分化的类群形成两个大的分支:一支是由露兜树目和薯蓣目构成,二者形成姐妹群关系;另一支是由天门冬目、百合目和鸭跖草类复合群组成,三者之间的关系在单个序列分析和联合分析中不稳定,需要进一步扩大取样范围来确定。在鸭跖草类复合群分支内,鸭跖草目和姜目的姐妹群关系在3个序列联合分析和2个序列联合分析的严格一致树中均得到强烈的自展支持,获得的支持率均是100%。但是,对于棕榈目和禾本目在鸭跖草类中的系统位置以及它们和鸭跖草目-姜目之间的关系,有待进一步解决。值得注意的是,无叶莲科与其他单子叶植物类群(除菖蒲目和泽泻目外)的系统关系在本文中获得较高的自展支持率,薯蓣目和天门冬目的单系性在序列联合分析中都得到了较好的自展支持,而这些在以往的研究中通常支持率较低。鉴于菖蒲科和无叶莲科独特的系统演化位置,本文支持将其分别独立成菖蒲目和无叶莲目Petrosaviales的分类学界定。

Two chloroplast （matK and rbcL）, and one nuclear （18S） genes from 86 families, 126 genera, and 151 species of angiosperms （including 58 families, 86 genera, and 101 species of monocots）, representing all major lineages of monocots and the basal angiosperms, were analyzed using parsimony methods. The eumagnoliids composed of Magnoliales, Laurales, Canellales, and Piperales appear as sister to the whole monocots. The monophyly of monocots receives 98% bootstrap support in the combined analyses of three genes. The monophylies of nine clades of monocots （Alismatales s.l., Dioscoreales, Pandanales, Asparagales, Liliales, Arecales, Poales, Zingiberales, and Commelinales） and six clades of other angiosperms （Nymphaeales, eudicots, Magnoliales, Laurales, Piperales, and Canellales） were supported in the strict consensus tree of combined analyses. The results showed that the genus Acorus is the basalmost clade among extant monocots, followed by Alismatales s.l. （including Araceae and Tofieldiaceae）. Petrosaviaceae are placed as a sister group of the clade comprising the Dioscoreales-Pandanales clade, Asparagales, Liliales and commelinoids. The sister-group relationships are strongly supported between Petrosaviaceae and the remaining monocots （except for Acoraceae and Alismatales s.l.）, between Dioscoreales and Pandanales, and between Commelinales and Zingiberales in the combined analyses of two genes and three genes. However, the phylogenetic relationships among Asparagales, Liliales and commelinoids are still uncertain in current analyses. In commelinoids, the relationships of. Arecales and Poales still need more research in future. Furthermore, it is noteworthy that the sister relationship between Petrosaviaceae and the remaining monocots （except for Acoraceae and Alismatales s.l.） and the monophylies of Dioscoreales and Asparagales were strongly supported with bootstrap values more than 90%, which generally received bootstrap values less than 50% in the previous studies. Considering the special position of Acoraceae and Petrosaviaceae, we support the taxonomical treatment of Acoraceae and Petrosaviaceae in their own order Acorales and Petrosaviales.