基于形态学特征和分子数据的中国缺齿藓科初步研究

为探讨缺齿藓类与真藓科、提灯藓科的系统关系,理清缺齿藓科的系统位置和中国缺齿藓科分类问题,该研究以中国分布的缺齿藓科植物和相关类群4 000余份标本为材料,进行详细的形态学研究,并选用其中35种、40份样品的4个DNA片段(rps4、trnG、trnL-trnF、atpB-rbcL)联合数据用于分子系统分析,采用邻接法(NJ)和最大似然法(ML)构建分子树。结果表明:(1)在分子树中,缺齿藓类与真藓科植物分别聚在具有高支持率的不同分支上,叶形、叶细胞等形态学特征也有较大差异,缺齿藓类应从广义的真藓科分出。(2)在分子树中,虽然缺齿藓类与提灯藓科植物聚在同一分支中,但无形态学的共源性状,二者不应视为一个单系类群。(3)缺齿藓科是一个自然类群,缺齿藓科内属间存在着密切的系统关系,缺齿藓科的主要识别特征为:植物体小型,茎常分枝;叶形和叶细胞为丝瓜藓型(Pohlia-like),披针形至长椭圆形,中上部细胞狭长,线状菱形或蠕虫形;生殖苞多生于新生枝顶;蒴齿为互生双齿层,常有不同程度的退化或一层蒴齿缺失,稀双层蒴齿缺失。(4)中国缺齿藓科包含有5属,即缺齿藓属(Mielichhoferia)、丝瓜藓属(Pohlia)、拟丝瓜藓属(Pseudopohlia)、合齿藓属(Synthetodontium)和小叶藓属(Epipterygium),目前为止共计34种(含种下分类单位)。

Phylogeny and Classification of the Moss Family Mielichhoferiaceae in China Inferred from Chloroplast DNA Sequences and Morphology

The paper aims to discuss the relationship between Mielichhoferia group and Bryaceae, to identify morphological synapomorphy between Mielichhoferia group and Mniaceae, to solve the problem of systematic position of Mielichhoferia group, to figure out the classification of Mielichhoferiaceae in China. Morphological characters of more than 4 000 specimens of Mielichhoferiaceae and its related groups in China were analyzed. And then, neighbor joining (NJ) and maximum likelihood (ML) tree were built based on combined trnG, rps4, trnL trnF, and atpB rbcL cpDNA sequences of 40 specimens for 35 species. Combining morphological and molecular data in the analyses showed that: (1) not only were Mielichhoferia group and Bryaceae family in the different clades in the molecular tree, but also morphological features, such as the leaf shape, the leaf cells of the two groups were different. Mielichhoferia group should be separated from Bryaceae. (2) No morphological synapomorphy can be detected for Mielichhoferia group and Mniaceae family, although they were in the same clade in the molecular tree. The two groups were not monophyletic. (3) Mielichhoferiaceae is a natural monophyletic group. In Mielichhoferiaceae, the plants are small, stems tend to be much branched than in Bryaceae; leaves are Pohlia like in shape and areolation; gametangia are often produced on lateral branches or the base of stems; peristome is diplolepideous alternate, often reduced to one layer or rarely absent. (4) There are five genera, Mielichhoferia, Pohlia, Pseudopohlia, Synthetodontium and Epipterygium, in Mielichhoferiaceae in China, total 32 species and 2 variaties.