莎草科薹草属宽叶薹草组及其近缘类群的系统学研究

The tribe Cariceae (Cyperaceae), with more than 2000 species, is one of the largest group of seed plants in the northern temperate zone. The plants of the tribe are important components of the vegetation of wetlands, grasslands and alpine meadows in the Northern Hemisphere. It has been discovered recently by molecular systematic study that Carex sect. Siderostictae and closely related groups form the basal clade of the tribe Cariceae, Siderostictae Clade.The plants of the clade are distributed in East Asia, mostly in China. Siderostictae clade is crucial for taxonomic, systematic and evolutionary study of the tribe Cariceae. There are about 39 species or varieties within the clade, and 29 species or varieties (21 endemic) in China. Up to now, only 9 species of the clade were sampled in molecular systematic or cytological study. The systematic study of the clade is insufficient, and there remains three systematic problems of the Clade to be solved urgently. Firstly, the circumscription of the clade is uncertain, and its taxonomic grade is undetermined. Secondly, the phylogenetic relationships are unclear among the groups within the clade. Thirdly, the taxonomic treatments of some species within the clade are quite confused. Based on extensive field surveys of populations and specimen studies in herbaria, we will collect specimens of Carex sect. Siderostictae and related groups, fix experimental materials for cytological and molecular studies, observe the morphological variation within and among populations, statistically analyse the variation of morphological characters, discuss the relationships between the morphological variation and the geographic distribution pattern, and evaluate the systematic significance of each kind of morphological characters. Meanwhile, we will study the anatomy of leaves and culms, observe the micromorphology of utricles and nutlets by SEM, count chromosome numbers and analyse karyotype, and sequence nrDNA ETS and ITS and cpDNA trnL-F. Molecular phylogenetic trees of tribe Cariceae will be built. According to molecular phylogeny and cytological study, Siderostictae Clade will be circumscribed, and phylogenetic relationships among the groups within the clade will be revealed. A reasonable taxonomic grade will be given to the clade by comparing it with other groups of the tribe Cariceae. In view of overall understanding of all these kinds of evidences, combining the understanding of phylogenetic relationships, we will revise the classification of Carex sect. Siderostictae and related groups, and clarify the taxonomic confusion of the problematic species and varieties. By examining the protologue and type specimens, the correct name of each taxon will be determined. The study of the present project will provide a clue for answering the important questions of the taxonomy, systematics and evolution of the tribe Cariceae.

莎草科薹草族是北温带物种多样性最丰富的类群，为北半球湿地、草原及高山植被的重要组成成分。薹草属宽叶薹草组及其近缘类群是近来分子系统学研究发现的该族最基部的分支，分布于东亚，大多数产于中国。宽叶薹草组及其近缘类群是研究薹草族分类、系统、起源与进化的关键，但由于对该类群研究相对薄弱，有3个系统学问题亟待解决。一是该基部分支的范围和分类等级待定，二是分支内各类群的系统发育关系不明，三是部分物种的分类混乱。针对上述3个问题，拟对宽叶薹草组及其近缘类群进行全面的野外考察，采集标本，获取染色体观察和DNA测序等实验材料。综合分析形态性状、染色体资料和DNA序列，构建系统发育树，确定薹草族基部分支的范围和分类等级，探讨其中各类群的系统发育关系。通过标本研究和野外居群观察，对形态性状做统计分析和比较研究，选择可靠的分类性状进行分类学处理，澄清物种分类的混乱。本研究将为解决薹草族系统与进化问题提供重要线索。

莎草科薹草族是北温带物种多样性最丰富的类群，为北半球湿地、草原、高山、苔原及林下植被的重要组成成分。薹草属宽叶薹草组及其近缘类群是近来分子系统学研究发现的该族最基部的分支，分布于东亚，大多数产于中国。宽叶薹草组及其近缘类群是研究薹草族分类、系统、起源与进化的关键类群，但由于对该类群研究相对薄弱，有3个系统学问题有待解决。一是该基部分支的范围和分类等级待定，二是分支内各类群的系统发育关系不明，三是部分物种的分类混乱。针对上述3个问题，本项目对宽叶薹草组及其近缘类群进行了全面的野外考察，采集标本，获取了大量解剖学和DNA测序等实验材料。通过综合分析形态性状、解剖学性状、DNA序列和70个样品的叶绿体基因组数据，构建了薹草族可靠的系统发育框架，确定了薹草族基部分支的范围包括薹草属的5个组，其中有3个组均非单系；而宝兴薹草组是薹草族基部分支中其余4组的姐妹群，而非整个薹草族的姐妹群。通过标本研究和野外居群观察，对形态性状进行统计分析和比较研究，综合本项目研究所做的系统发育分析，支持将薹草族各属合并为广义的薹草属，并建议将广义薹草属分为4个亚属，宽叶薹草组及其近缘类群组成的基部分支为其中的一个亚属。根据本项目研究结果，对宽叶薹草组及其近缘类群中分类混乱的物种进行了分类学修订，完成了泛喜马拉雅地区薹草属的分类学研究，并编写完成泛喜马拉雅植物志，已于2019年底出版。本研究将为解决薹草族系统、进化和分类问题提供重要线索和依据。