Taxonomic Note And Floristic Geographical Study On Astragalus.L In Mongolian Plateau

The genus Astragalus L. with nearly3000species, is probably the largest genus amongthe flowering plants. The majority of species are found in the temperate semiarid and aridcontinental regions of south-western and central Asia, the Sino-Himalayan region, westernNorth America, and along the Andes in South America. In Mongolian Plateau, there are about110species, mainly distributed in the steppe and desert vegetation zone of this region. Forsome reasons, there are many taxonomic problems unresolved among these species. In thisstudy we revised some of these species based on the inter-simple sequence repeat (ISSR)makers and the internal transcribed spacers (ITS). Genetic relationship among45Astragalusaccessions of9specieses was analyzed using ISSR primers.11ISSR primers generated a totalof188valid loci, of which178were exhibited polymorphism, and the percentage ofpolymorphic bands was94.7%. Cluster analysis based on unweighted pair-group method wasconducted using the NTsys2.10e software. Internal transcribed spacers of20accessions weresequenced, and the lengths of which were667-673bp, average667.8bp. Treating the speciesof Oxytropis as outgroup, phylogenetic analyses were conducted using MEGA ver.5.1software based on Maximum-parsimony (MP) and Neighbor-Joining (NJ) methord,respectively. The list of Astragalus in Mongolian Plateau has been established. Floristicgeographical element and relationship with other distribution ranges of Astragalus L.have alsobeen analyzed. The main results are as follows：1．Astragalus ningxiaensis and A. koburensis were treated as the synonyms of A.galactites. The first two species were only variant or ecotypes of A. galactites and not newspecies;2. A. limprichtii and A. leansanicus were two relative species. It’s reasonable to treatthem as two independent species which belong to the same section of Onobrychides.3. Support the conclusion of treating A.ordosicus as a synonym of A.grubovii. Therewere no sequence variations between their internal transcribed spacers, so they were probablythe same species;4. Phylogenetic analyses based on ITS sequence showed that not all of the8subgeneraof Astragalus L.were monophyletic groups. The result sported the idear of “Flora of China (V10)”, organizing the species at section level, but some species’s ownership shoud bemodified;5. In Mongolian Plateau there were about112species of Astragalus L., which belongedto38sections;6.112species of Astragalus L. belonged to7different floristic geographical elements,including Pan-north pole element, east Palaeo-north pole element, Palaeo-Mediterraneanelement, Central Asian element, Dahuri-Mongolia element, Mongolian-Loess Plateauelemengt and Endemic element. These species had close relationship with the species ofcentral Asia including Xinjiang, and they were the extension of central Asia species. Somenew species formed and interacted with the species of the adjoining areas, which enriched thefloristic geographical elements of Mongolian Plateau.