Systematic Studies On The Tribe Of Zoysieae (Poaceae)

The tribe of Zoysieae Miq. which belongs to the family Poaceae, about 300 species, widely distributed in tropical and subtropical temperate regions of the world and 3 genera, ten species in China. Due to its unique morphology and leaf anatomy structure, the systematic status of Zoysieae has still a great mater of debate. In this thesis, the systematic status of Zoysieae has been documented by means of leaf abaxial epidermis, caryopsis and silica body morphology, and molecular systematics, which provide new evidences for systematic position of Zoysieae.Light microscopes are used to examine leaf epidermal features, caryopsis and silica body morphology of the tribe of Zoysieae and related genera of fam. Poaceae. Through the study, we found that costal zones of Perotis markedly wider than Tragus and Zoysia; There are papillaes and not short cells over the veins in Tragus. It defferes obviously from Zoysia. Caryopsis morphology of subfam. Eragrostoideae belong to the type of Eragrostideae, but the mode of Caryopsis compression of Tragus conforms with the type of Panicoideae. The silica bodies of subfam. Perotis is the type of Panicoideae, the other genera is Eragrostideae. Especially, the variety of the silica body of Zoysia is obvious, from saddle to crescentic, roundness. In leaf abaxial epidermis, caryopsis , silica body morphology and their unique morphology and leaf anatomy structure, there is respectively characteristic in Perotis, Tragus and Zoysia.However , Perotis, Tragus and Zoysia are united into Chloridoideae.Molecular phylogeny. The systematic rank of Zoysieae is discussed and examined the phylogenetic relationships between this tribes and related genera in the Poaceae using ITS and trnL-F DNA fragment. The results show that Poaceae formed monophyletic group comprised of four clades, cladeA, B, C, D. Of these, clades A, B, C, D correspond with subfam. Eragrostoideae, Panicoideae Arundinoideae and Pooideae. In the clade A, the subfam. Eragrostideae is not monophyletic. Perotis, Tragus and Zoysia are also in the latter , so it is close relationship with the Chlorideae. Besides, that many sister clades in the Chlorideae are refered as the subtribes needed more evidence to clarify.In conclusion, Based on Leaf abaxial epidermis, Caryopsis morphology, Silica body, Molecular phylogeny, the present tresults differ from the tradtional study indicate that Perotis, Tragus and Zoysia are immerged into Chloridoideae the subfam. Eragrostis, the tresults of this thesis support the conclusion of Flora of China (Zhou T-Y et al, 2001) and the three genera is not independently treated as a tribe.Eragrostideae is not monophyletic,how Chloridoideae devides subtribes need more evidence to clarify.