Taxonomic revision of Chordaria flagelliformis (Chordariales, Phaeophyceae) including novel use of the intragenic spacer region of rDNA for phylogenetic analysis
Taxonomic revision of Chordaria flagelliformis (Chordariales, Phaeophyceae) including novel use of the intragenic spacer region of rDNA for phylogenetic analysis
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Chordaria flagelliformis（Chordariales、Phaeophyceae）的分类学修订，包括新使用 rDNA 的基因内间隔区进行系统发育分析
DOI：
10.2216/i0031-8884-41-4-328.1
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发表时间：
2002
期刊：
影响因子：
1.6
通讯作者：
H. Kawai
中科院分区：
文献类型：
--
作者：
Sung‐Ho Kim;H. Kawai
摘要鞭毛状脊索藻广泛分布于北半球的冷水区、北冰洋沿岸、大西洋沿岸和太平洋沿岸。鞭毛尾藻是由斯皮茨卑尔根的Kjellman首先描述的四个新的形态类型之一，其特征是具有简单的叶状体(不分枝或分枝很少)，在较冷的水域的分布范围似乎比典型的鞭毛藻(F.flagelliformis)分布范围较窄。然而，用于区分这一变型的分类特征并不总是可靠的，因为该种的形态可塑性很大。利用5.8S、内转录间隔区(ITS)和基因内间隔区(IGS，位于26S和5S之间)rDNA区和Rubisco(几乎完全的rbcL基因及其在rbcL和RBC之间的间隔区)进行的分子系统发育分析表明，鞭毛藻由三个主要遗传群组成：群1(来自北太平洋堪察加的脊索藻)、群2(来自其他地区的脊索藻)和群3(鞭毛藻)。“群2”和“群3”由两个亚群组成，分别对应于它们的大西洋和太平洋种群。ITS1和ITS2区序列长度在各组和亚组中相对恒定，组间差异较大。这是首次报道利用26S-5S IGS区域进行分子系统发育分析；该区域的可变性是5.8S-ITS区域的三到八倍。在这些分析的基础上，得出结论：鞭形花卉表现出很大的形态可塑性，并包含一些不分枝的标本，而脊状花序花卉在分枝数量上更一致。虽然堪察加地区与其他地区的种群之间的分类关系尚不清楚，但鞭状脊索虫是独立于狭缝鞭毛虫的。我们建议在种的水平上将其识别为C.chordaeformis(Kjellman)Kawai&S.H.Kim stat。11月
Abstract Chordaria flagelliformis is widely distributed in the cold-water areas of the Northern Hemisphere, along the Arctic, Atlantic and Pacific coasts. Chordaria flagelliformis f. chordaeformis, one of the four new morphological forms first described by Kjellman from Spitsbergen, is characterized by its simple thallus (unbranched or with very few branches) and appears to have a narrower distributional range in colder-water areas compared to the typical form (f. flagelliformis). However, the taxonomic character used to distinguish this form is not always reliable, because of the great morphological plasticity of the species. Molecular phylogenetic analyses using the 5.8S, internal transcribed spacer (ITS) and intragenic spacer (IGS, between 26S and 5S) rDNA regions and Rubisco (almost complete rbcL gene and its spacer region between rbcL and rbcS) showed that C. flagelliformis is composed of three major genetic groups: ‘group 1’ (f. chordaeformis from Kamchatka, north Pacific), ‘group 2’ (f. chordaeformis from other areas) and ‘group 3’ (f. flagelliformis). ‘Group 2’ and ‘group 3’ were composed of two subgroups, corresponding to their Atlantic and Pacific populations. The lengths of the sequences of the ITS1 and ITS2 regions were relatively constant in each group and subgroup, and were considerably different between groups. This is the first report of the use of the 26S-5S IGS region for molecular phylogenetic analysis in any organism; the region was shown to be three to eight times more variable than the 5.8S–ITS region. On the basis of these analyses, C. flagelliformis f. flagelliformis was concluded to exhibit great morphological plasticity and to contain some specimens that are unbranched, whereas f. chordaeformis was more consistent in the number of branches. Chordaria flagelliformis f. chordaeformis is independent from C. flagelliformis sensu stricto, although the taxonomic relationships between the populations of Kamchatka and other areas are still unclear. We propose recognizing f. chordaeformis at the species level, as C. chordaeformis (Kjellman) Kawai & S.H. Kim stat. nov.