The Studies Of Phylogenetic Relationship And Classification Of Cleistogenes And Relatives (Poaceae)

The genus Cleistogenes(Poaceae)distribute predominately in the north of China and most of them are eminent forages and sand binders,which identified Cleistogenes serotina(L.)Keng as model plant.This genus consist approximately 11 species according to Flora of China,especially 5 endemic species in China.Many previous studies have shown inconsistent results regarding to the classification of interspecies and phylogenetic position of Cleistogenes and relationships among their sister groups.In this study,we aimed to figure out the phylogenetic position of Cleistogenes and interspecies relationships of this genus.We selected about 55 samples of micromorphological characters of lemmas with the aid of SEM.The microcharacters which were designed based on the condition of relatively stable and obviously variation,such as long cells,short cells,silica bodies,stomatal subsidiary cells,prickle hairs,hooked hair,micro-hairs and macro-hairs.The typical microcharacters of them,such as short cells,prickle hairs,hooked hair,micro-hairs and macro-hairs,were performed to distinguish the difference of interspecies.The basal microcharacters of Cleistogenes,such as tubular-shaped long cells with papillary incrassation,dumb-bell shape of silica bodies,flat-topped to low dome-shaped subsidiary cells,costal large prickles and intercostal medium prickles,cuneate shape of two-celled micro-hairs and macro-hairs.We proposed five types to represent total samples,type ? consisted of subfamily Chloridoideae,type ? corresponded subfamily Panicoideae,type ? included subfamily Arundinoideae and Micrairoideae,type ? represented subfamily Pooideae and type ? was consistent with subfamily Oryzoideae.The type ? representing two evolutionary directions showed four micromorphological types including Eragrostidoid-type,Sporoboloid-type,Cynodontoid-type and Cleistogenoid-type.We suggested to place Cleistogenes in Chloridoideae based on micromorphological characters of the lemma.To investigate phylogenetic relationships of Cleistogenes and related genera,we selected about 57 samples in China covering undisputed BOP and PACMAD clades,using nuclear ribosomal internal transcribed spacer(ITS1-5.8SrDNA-ITS2),two plastid sequences(trnL-trnF intergenic spacer region and rbcL)and the combined data sets.Maximum likelihood(ML),maximum parsimony(MP)and Bayesian methods(BI)were conducted.We supported to accept the classification of subtribe Zoysiinae(genus Zoysia)and Sporobolinae(genus Sporobolus,Crypsis and Spartina)in tribe Zoysieae.The closely genetic relationship between genus Enneapogon and Eragrostis was also showed clearly.We proposed to place Cleistogenes out of tribe Eragrostideae,because of further evolutionary distance and the both ends positions of phylogenetic tree of subfamily Chloridoideae.It was more reasonable to place it in tribe Cynodonteae.We proposed to establish subtribe Cleistogeninae that consisted of genus Cleistogenes and Orinus locating in tribe Cynodonteae(Chloridoideae)as sister to subtribe Tripogoninae.The combined DNA tree yielded four delimitation of Cleistogenes representing all samples.Combined morphological and phylogenetic evidences we supported Cleistogenes mucronata as a synonym of Cleistogenes festucacea and Cleistogenes hackelii var.nakaii as a variation of Cleistogenes hackelii var.hackelii,proposed Cleistogenes brevipolea and Cleistogenes caespitosa var.romosa not to determine taxon because of without enough evidences.The results showed that three new taxon,Cleistogenes gracilis,Cleistogenes kitagawai var.foliosa and Cleistogenes longiflora,should be published and supported the previous taxon,such as Cleistogenes squarrosa,Cleistogenes caespitosa,Cleistogenes festucacea,Cleistogenes hancei,Cleistogenes hackelii,Cleistogenes polyphylla,Cleistogenes kitagawae and Cleistogenes songorica.