Molecular phylogeny of extant gymnosperms and seed plant evolution: Analysis of nuclear 18S rRNA sequences
Molecular phylogeny of extant gymnosperms and seed plant evolution: Analysis of nuclear 18S rRNA sequences
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DOI：
10.1093/oxfordjournals.molbev.a025702
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发表时间：
1997-01-01
影响因子：
10.7
通讯作者：
Li, WH
中科院分区：
文献类型：
--
作者：
Chaw, SM;Zharkikh, A;Li, WH
为了研究现存裸子植物四种目之间的进化关系以及每个目中的科间关系，使用邻接法和最大简约法分析了来自蕨类植物、裸子植物和被子植物的一组 65 个核 18S rRNA 序列。以卷柏为外类群，分析有力地表明种子植物与蕨类植物形成单系类群。在种子植物中，被子植物显然是一个单系类群。尽管对裸子植物进化枝单系性的自举支持是中等的，但单系性因其缺乏被子植物特异性插入缺失而得到进一步支持。在裸子植物中似乎存在三个单系分支：苏铁目-银杏目、买麻藤目和松柏目。苏铁-银杏分支是最早的裸子植物谱系。鉴于买麻藤目和松柏目之间姐妹群关系的强烈支持，买麻藤目不太可能是被子植物的姐妹群，这与许多植物分类学家的观点相反。在松柏目中，松科是单系的，是其余针叶树科的基部，其中有三个单系分支：叶柄科-罗汉松科、南洋杉科和杉木科-红豆杉科-三尖杉科。在后一个分支中，杉木科可能是其他四个科的外类群。在被子植物中，在亚纲水平上没有发现明显的簇，但有证据表明睡莲科首先分枝。在其余的被子植物中，本研究中包括的单子叶植物是嵌套的并形成单系群。这项研究证明了核 18S rRNA 序列在解决活体裸子植物之间关系方面的效用。在蕨类植物和种子植物中观察到替代率存在相当大的差异。
To study the evolutionary relationships among the four living gymnosperm orders and the interfamilial relationships in each order, a set of 65 nuclear 18S rRNA sequences from ferns, gymnosperms, and angiosperms was analyzed using the neighbor-joining and maximum-parsimony methods. With Selaginella as the outgroup, the analysis strong ly indicates that the seed plants form a monophyletic group with the ferns as a sister group. Within the seed plants the angiosperms are clearly a monophyletic group. Although the bootstrap support for the monophyly of the gymnosperm clade is moderate, the monophyly is further supported by its lack of angiosperm-specific indels. Within the gymnosperms there appear to be three monophyletic clades: Cycadales-Ginkgoales, Gnetales, and Coniferales. The cycad-ginkgo clade is the earliest gymnosperm lineage. Given the strong support for the sister group relationship between Gnetales and Coniferales, it is unlikely that Gnetales is a sister group of the angiosperms, contrary to the view of many plant taxonomists. Within Coniferales, Pinaceae is monophyletic and basal to the remaining conifer families, among which there are three monophyletic clades: Phyllocladaceae-Podocarpaceae, Araucariaceae, and Sciadopityaceae-Taxaceae-Cephalotaxaceae Within the latter clade, Sciadopityaceae may be an outgroup to the other four families. Among the angiosperms, no significant cluster at the level of subclass was found, but there was evidence that Nymphaeaceae branched off first. Within the remaining angiosperms, the monocots included in this study are nested and form a monophyletic group. This study attests to the utility of nuclear 18S rRNA sequences in addressing relationships among living gymnosperms. Considerable variation in substitution rates was observed among the ferns and seed plants.