Phylogeny Study And Taxonomic Revision Of Impatiens Subg. Clavicarpa

The subg.Clavicarpa S.X.Yu & Wei Wang is the basic group of Balsaminaceae Impatiens,including about 30 species,which are mainly distributed in Southwest China,especially in Guangxi and Yunnan.Up to now,the phylogenetic relationship of this subgenus is still unclear,and there are still outstanding problems within the subgenus,such as unclear species,difficult to define between species,and inconsistent names and realities.Therefore it is helpful for us to understand the origin and evolution of this subgenus by studying its morphological characters and phylogeny.In this study,based on the investigation of domestic and foreign museum specimens and field work,the variation range and law of morphological characters of this subgenus were studied at population level and species level,and the phylogenetic relationship of the subgenus was reconstructed by combining the seed micromorphological characteristics and molecular evidence.Under the framework of phylogeny,the subg.Clavicarpa was taxonomic revised.The results are as follows:1.The research results of the variation law of the key morphological traits of subg.Clavicarpa show that:(1)The variation of morphological traits of flowers within subgenus is complex and relatively stable within species,thus can be used as an important classification basis for the definition of species within the subgenus;(2)The research also shows that certain characteristics: such as 4 lateral sepals,clavate fruit,etc.,are relatively stable within the subgenus.These traits have important taxonomic value for the definition of this subgenus.2.Studies on seed micromorphology of 16 species of subg.Clavicarpa show that:(1)the seeds of subg.Clavicarpa were ellipsoid or narrow ellipsoid.The ratios of length to width are mostly between 1.4–2.3,the seedcoat with simple reticular ornamentation.The seed morphology and seedcoat micromorphology of this subgenus are relatively stable at the subgenus level,which has a certain significance for the establishment of phylogenetic relationship of this subgenus.(2)The seed morphology and seedcoat micromorphology of this subgenus have a strong correlation with the macroscopic morphological characters.But the stability and specificity of whether there are granules in the lumina,whether the reticular ridge is obvious,and whether the top of the reticular ridge is straight or curved within species are not obvious,which have limited significance in circumscription of species within subg.Clavicarpa.3.24 species(49 samples)of subg.Clavicarpa were sampled and phylogenetic analysis was carried out by using two nuclear gene fragments(ITS and ImpDEF2)and four chloroplast fragments(atp B-rbc L,trn L-F,matk,psb A-trn H).The results showed that the subg.Clavicarpa was a monophyly of Balsaminaceae with high support value.Phylogenetic trees of nuclear genes and chloroplast genes all indicate that subg.Clavicarpa appears as the base clade of Impatiens,and the branch length of phylogenetic trees is very short,which proves that this subgenus is a relatively primitive group of Impatiens.The phylogenetic tree of nuclear genes showed that I.maculifera formed a sister group with the rest species in the subgenus;I.clavigera and I.parvisepala,I.malipoensis and I.apalophylla,I.guizhouensis and I.pterocaulis form sister groups two by two respectively.The phylogenetic tree of chloroplast genes showed that I.clavigera form a sister group with the rest species in the subgenus;I.tonglingensis and I.hongkongensis form a sister group,and then they form a sister group with I.parvisepala;I.macrantha and I.chishuiensis form a sister group;I.omeiana,I.pritzelii,I.qingchengshanica and I.wilsonii gather in a small branch and the kinship within them are closer.According to the distribution of this subgenus,which is mainly distributed in Guangxi,Yunnan,and also found in the north of Vietnam,combined with the previous research results,this study speculates that the south of China and the north of Vietnam are the origin of Impatiens,and thus spread in many directions.4.Based on the last 1000 trees obtained from Bayesian analysis of nuclear genes in phylogenetic relationship research,4 selected key morphological characters(leaf shape,petiole,flower color and spur shape)were added to reconstruct the ancestral morphological character.The results show that all the 5 morphological characters selected in this study can be used as the basis for the classification of this subgenus,but they do not show strong systematic significance,which indicate that the significance of these characters in species definition is greater than its systematic value.5.This study based on a large number of specimen inspections and field investigations at the population level and species level,exploring the variation range and law of morphological traits,and combining with the study of seed micromorphology,under the framework of phylogeny constructed using molecular evidence,the classification of subg.Clavicarpa have been comprehensively revised.The results showed that: 27 species,1 variety recognized in subg.Clavicarpa,including 4 new species and 1 new variety,and 1 new combinations were proposed;7 doubtful species are contained in this subgenus.This study also clarified the previous false descriptions of the I.chishuiensis and I.spathulata.Color plate of each new species and new varities in subg.Clavicarpa were provided.