中文摘要：

世界范围内报道的全部串珠藻目种类均生活于淡水中, 而在淡水红藻中, 70%约有130种属于串珠藻目。研究以目前获取的来自世界各大洲串珠藻目植物43种的rbcL基因序列, 结合其形态和生物地理特征, 构建了该目的系统发育关系, 以期探讨整个串珠藻目植物的系统发育关系及发生途径, 进而为研究该目以至淡水红藻的起源提供基本资料。运用PAUP^＊4.0b10和Mr Bayes 3.0b4等软件对43种串珠藻目植物的叶绿体DNA rbcL基因序列进行系统发育分析, 探讨了其主要分类群的系统演化关系。用最大简约法、邻接法和贝叶斯分析方法构建的系统树基本一致, 结果显示： （1）基于分子数据分析结果显示, 红索藻目植物均独立于串珠藻目植物, 构成一个单独的分支, 支持红索藻目的建立。（2）鱼子菜科属于串珠藻目植物中较为进化的类群。（3）串珠藻属扭曲组与杂生组的差异度较小, 结合其形态特点, 倾向于将杂生组并入扭曲组。（4）串珠藻科属于串珠藻目中最大的科, 包括较多的种类, 其系统关系也较为复杂。因此, 串珠藻科系统发育关系的明确有待于进一步结合更多的分子数据和形态学特征加以分析研究。

英文摘要：

Batrachospermales is an order belonging to Florideophceae, Rhodophyta. It distributes all over the world, China and its adjacent regions are the distribution center. Since Batrachospermales has been reported, the studies about the order were mainly focused on their morphological characters and its flora. But the phylogenetic relationship between taxa of Batrachosperales was still hard to guarantee in terms of morphology. Chloroplast rbcL sequences from 43 species of Batrachospemales and their relative lineages were used to reconstruct the phylogenetic trees by using the PAUP^＊ 4.0 b10 and Mr Bayes 3.0 b4 software, which contained 6 samples collected from China and 37 species abroad obtained from GenBank. The phylogenetic relationships were inferred using the neighbor-joining, maximum-parsimony and Bayesian analysis, and three methods produced trees with largely congruent topology. These trees revealed that： （1） Three kinds of phylogenetic trees based on rbcL sequences were consistent. All phylogenetic trees topology got a similar placement of Thoreales, which formed a monophyletic group with high bootstrap support （100%）. According to the Bayesian analysis, the conclusion supported that the Thoreales should be classified as a separate order. Thoreales were distinguished from Batrachospemales based on having freshwater representatives with multiaxial gametophytes, a uniaxial chantransia stage, and pit plugs with two cap layers, the outer one of which was usually plate-like. （2） All phylogenetic trees, got from the three methods （MP, NJ and Bayesian）, showed that the Lemaneaceae was a relatively evolutional group in Batrachospemales. Two genera （Lemanea and Paralemanea）, which belonged to family Lemaneaceae, formed new branches respectively, both of which were sister group. （3） In all trees, the taxa of Sirodotia and Tuomeya clearly formed a monophyletic clade with a strong bootstrap support, showed that they were relatively evolutional group in Batrachospemales. The two species of the N