Phylogeny, systematics, biogeography and evolution of the genus Suaeda, subgenus Brezia (Chenopodiaceae)

本项目旨在阐明藜科碱蓬属Brezia亚属的系统发育、系统分类、地理分布和进化历史。盐生植物约有20 ~ 35种，几乎全世界都有分布。典型的栖息地是沿着海岸线的盐沼和草原和半沙漠地区的内陆洼地。我们认为碱蓬，亚属Brezia作为一个合适的模式系统破译全球分布的盐生植物的地理格局和过程。该亚属在分子系统发育树中形成了一个明确的单系分支，但根据其表型习性对其物种进行鉴定和区分是非常困难的。因此，物种的边界，系统发育关系和分布区的细节是不充分的了解。我们以前的工作表明，多倍性和杂交可能在该亚属的进化中起了相当大的作用。本研究将结合联合收割机的形态学、核型和DNA序列数据以及分子钟方法来回答以下问题：（1）有多少种Brezia属植物可以被清楚地划分和区分？(2)这些物种之间的系统发育关系是什么？它们的形成机制是什么？(3)该亚属的地理起源地在哪里？是什么样的迁徙路线和机制导致了其物种目前的分布格局？

Our project aims to elucidate the phylogeny, systematics, biogeography and evolutionary history of Suaeda, subgenus Brezia (Chenopodiaceae). With about 20 to 35 halophytic spe-cies, Brezia has an almost worldwide distribution. Typical habitats are salt marshes along coastlines and in inland depressions of steppe and semi-desert areas. We consider Suaeda, subgenus Brezia as a suitable model system for deciphering biogeographical patterns and processes of globally distributed halophytes. The subgenus forms a well-defined mono-phyletic clade in molecular phylogenetic trees, but the identification and discrimination of its species by their phenotypic habit is extremely difficult. Consequently, species boundaries, phylogenetic relationships and details of distribution areas are insufficiently known. Our pre-vious work indicated that polyploidy and hybridization may have played a considerable role in the evolution of the subgenus. In the present project, we will combine morphological, karyological and DNA sequence data as well as a molecular clock approach to answer the following questions: (1) How many Brezia species can be clearly circumscribed and differen-tiated from each other? (2) What are the phylogenetic relationships between these species, and which speciation mechanisms were involved? (3) Where did the subgenus originate geographically, and what were the migration routes and mechanisms that resulted in the pre-sent distribution patterns of its species?