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

本项目旨在阐明藜科（Chenopodiaceae）藜亚属（Suaeda）的系统发育、系统学、生物地理学和进化历史。布雷齐亚盐生植物约有20至35种，几乎分布在世界各地。典型的栖息地是沿海岸线的盐沼和内陆草原和半沙漠地区的洼地。我们认为Suaeda， Brezia亚属是一个合适的模式系统，用于解读全球分布的盐生植物的生物地理格局和过程。该亚属在分子系统发育树上形成了一个定义明确的单系分支，但通过其表型习惯对其物种进行鉴定和区分是非常困难的。因此，物种边界、系统发育关系和分布区域的细节还不够清楚。我们之前的工作表明，多倍体和杂交可能在亚属的进化中发挥了相当大的作用。在本项目中，我们将结合形态学，核学和DNA序列数据以及分子钟方法来回答以下问题：(1)有多少种布雷齐亚可以明确界定和区分？(2)这些物种之间的系统发育关系是什么，涉及哪些物种形成机制？(3)该亚属在地理上起源于何处？造成其物种分布格局的迁移路线和机制是什么？

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?