A molecular phylogenetic analysis of the fucalean brown algae based on RFLPs of chloroplast DNA.

虽然最初的计划是研究叶绿体DNA的RFLP，但我们已经将其改为核编码基因的DNA测序分析，因为测序技术就在项目开始之前就可以使用了。作为项目的起点，我们开发了一种从褐藻组织中提取PCR友好的DNA的技术，这通常被认为是困难的。以雄性花托为来源，成功地提取了PCR质量的总DNA。为了检验基于形态依据识别三科的日本岩藻分类系统的有效性，我们基于18SrDNA序列数据研究了岩藻目藻属的系统发育关系。共调查了该目7属10种。这些植物包括羊栖菜、马尾藻和马尾藻。结果表明，马尾藻与马尾藻分支(马尾藻科)有较高的自举支持度，与马尾藻属(Myagropsis)为姐妹群。因此，区分藻科和马尾藻科的形态特征(分枝方式)并不能反映系统发育关系。相反，卵原细胞内的卵发育模式被发现反映了根据18SrDNA序列推断的系统发育关系。利用ITS2序列研究了马尾藻科植物的系统发育关系。结果表明，Hizikia属的自主性是值得怀疑的。我们已经识别出马尾藻/Hizikia分支中的几个分支。然而，这些分支并不对应于现有的任何一个分类群，如马尾藻属内的亚属。形态研究表明，来自北海道的一个类似马尾藻的种是一个新种，我们将其描述为S.boreale sp.nov.

Although original plan was to investigate RFLPs of the chloroplast DNA,we have changed it to DNA sequencing analyzes of nuclear encoded genes, because the sequencing techniques became available just before start of the project. As the starting point of the project, we have developed a technique to extract PCR friendly DNA from the brown algal tissue, which is generally said to be difficult. We have successfully extract the total DNA of the PCR quality by using male receptacles as a source.In order to test the validity of the classification system of the Japanese fucalean algae which recognize three families based on morphological grounds, we have investigated phylogenetic relationship of the genera in the order Fucales based on 18SrDNA sequence data. Ten species belonging to 7 genera in the order were investigated. These include Fucus, Pelvetia (Fucaceae), Cystoseira, Coccophora, Myagropsis (Cystoseiraceae) Sargassum and Hizikia (Sargassaceae). The results revealed that the member of the Cystoseiraceae, Myagropsis come to the position sister group to the Sargassum/Hizikia clade (Sargassaceae) with high bootstrap support. Therefore, the morphological character (mode of branching) which separates the Cystoseiraceae from the Sargassaceae was found not to reflect phylogenetic relationship. Instead, the mode of egg development within a oogonium was found to reflect phylogenetic relationship deduced from the 18SrDNA sequences.The phylogenetic relationship within the family Sargassaceae was investigated using ITS2 sequences. The results revealed that autonomy of the genus Hizikia is dubious. We have recognized a few clades within a Sargassum/Hizikia clade. However, these clades do not correspond to any of the current taxa, such as subgenera within the genus Sargassum.Morphological study revealed that a species refereed Sargassum confusum-like sp.from Hokkaido was a new species and we described it as S.boreale sp.nov.