Study On The Taxonomy Of Two Small Genera Of Chinese Astereae

Astereae is the second largest family in Asteraceae,Myriactis and Dichrocephala are two small genera of the Chinese Astereae.But so far,many taxonomic issues such as whether it is a monophyly,its position in the Astereae,and the relationship between species within the genus have not been studied.This research is studies the genus Myriactis and Dichrocephala from the morphological anatomy and molecular systems.It aims to clarify the status of these two genera in the Astereae and the interspecific relationship between the two genera,and lay the foundation for further research in the future.1.Morphological and anatomical researchThis article explores the value of certain traits in taxonomy by observing the morphology of plants and dissecting the leaf epidermis.1.1 Morphological researchMorphological observation of 8 species of of Myriactis and Dichrocephala.The results showed that the morphology of leaves and ray flower has a certain taxonomic value between the two genera and species.By comparing the morphology between species within the two genera,it was found that:(1)Suspected hybrids of Myriactis.delevayi and M.nepalensis;(2)The morphology of the same population of M.wightii var.cordata is quite different;(3)The specimens of M.wallichii and Myriactis wightii did not differ from the flora description;(4)The Luojishan population of M.delevayi differed from other populations in leaf shape;(5)The Dichrocephala chrysanthemifolia is distinguished from the Dichrocephala other two by its ray florets pedicellate.1.2 Anatomical researchThe anatomical study of the leaf epidermis of these two genera and12 species of Aster.The results show that the type of leaf epidermal cells,the style of the vertical wall,the presence or absence,size and density of the stomatal apparatus have a certain taxonomic value among these genera,while the shape of the stomatal apparatus no obvious taxonomic value.1.Molecular systematic researchIn this paper,we use ITS,ETS and trn L-F data to study the molecular systematics of Myriactis and Dichrocephala.The results show that two genera are embedded in the Astereae and are both monophyly.The results of molecular phylogeny showed:(1)The parent and female parent of the M.hybrid are M.nepalensis and M.delevayi respectively.(2)The morphological difference of Myriactis wightii var.cordata are on one branch and belong to one species.(3)Myriactis wallichii and Myriactis wightii are on the same branch,it is inferred that they are homologous or the same,and may be considered for merging after further research in the future;We proposed the concept of compound of M.wightii,including M.wightii,M.wightii var.cordata and M.wallichii.In addition,the molecular comparison results of M.wightii and M.wallichii showed the similar dimorphism.Therefore,we speculated that it was a hybrid origin,but no matching parent was found.(4)The Myriactis delevayi from the Luojishan population and other populations are on one branch and belong to one species.(5)The three phylogenetic trees all show that Dichrocephala chrysanthemifolia is not on the same branch with the other two species of the genus Dichrocephala.It is recommended to separate it from the genus Dichrocephala and form a separate genus.2.Taxonomic treatmentOn the basis of morphological anatomy and molecular systematics,combined with literature and plant specimens,the first generation of natural hybrids(Myriactis delevayi × M.nepalensis W.P.Li et Q.Y.Zhao)are described and supplementary description of M.wightii var.cordata and M.delevayi.