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

点击翻译按钮获取中文摘要

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?