饶氏藻系统位置的研究

Studies on the Phylogenetic Placement of Jaoa

摘要:

用18S rDNA基因序列分析饶氏藻属(Jaoa)与相关藻类的亲缘关系。结果表明:饶氏藻18S rDNA的长度为1632 bp,GC%为50.6%,泡状饶氏藻18S rDNA的长度为1639 bp,GC%为50.3%。用最大简约法与饶氏藻上一级分类单元(目)构建的系统树表明有4个大的分支。两种饶氏藻与石莼目的Ulva curvata、U. rigida、Enteromorpha intestinalis和Monostroma grevillei构成很强的支持分支(分支B),它们之间的核苷酸趋异性最低仅0.041,而与胶毛藻目的Chaetophora incrassata的趋异性则很显著,达0.112,因此,饶氏藻应属于石莼目的一个类群,且饶氏藻和泡状饶氏藻构成一单系起源的分支,这两个物种的趋异性仅0.002,显示出它们具有非常紧密的亲缘关系,很可能是1种1变种而不是2种。

关键词:饶氏藻;18S rDNA;系统分类位置;石莼目;胶毛藻目

Abstract:

Jaoa is an endemic group of fresh water algae in China. The phylogenetic relationship between Jaoa and related algae by using 18S rDNA sequences was studied. The result showed that the length of 18S rDNA of J. prasina is 1632 bp and GC% is 50.6%, and those of J. bullata are 1639 bp and 50.3%, respectively. The maximum parsimonious tree indicated that Jaoa with its related Orders could be divided four Clades. Jaoa prasina, J. bullata, Enteromorpha investinalis, Ulva curvata, U. rigida and Monostroma grevillei constituted strong supported clade (Clade B), among which the lowest nucleotide divergence was 0.041, while that reached up 0.112 between J.prasina, J. bullata and Chaetophora incrassata. Therefore, Jaoa probably belongs to Ulvales. Jaoa prasina and J. bullata constitute a monophyletic branch (100% bootstrap value) in Clade B with divergence of 0.002. It suggested that the two species of Jaoa are closely related species, they might be one species and one variety.

Key words:Jaoa;18S rDNA;Phylogenetic placement;Ulvales;Chactophorales