Phylogeny And Functional Character Evolution Of Stipa In China

The zonal Stipa grassland community formed by Stipa is the main part of Eurasian grassland and plays a very important role.Therefore,studying Stipa has important ecological and economic significance.The purpose of this paper is to reveal the phylogenetic relationship of Stipa genus and the adaptive evolution process of the functional traits of Stipa genus to the external environment.Therefore,20 species of Stipa in the central Asia and Qinghai-Tibet plateau sub-regions of Eurasia grassland were taken as objects in this study.Data of 30 functional traits,such as plant height,specific leaf area,elongated needle length,leaf carbon content and nitrogen content,were collected.The phylogenetic tree of Stipa was constructed based on DNA barcode,and the phylogenetic status of Stipa was discussed.SPSS was used to analyze the functional traits of the two prairie sub-regions.Then the phylogenetic tree of Stipa was combined with functional traits,and the phylogenetic signals of functional traits were tested by K-value method.The ancestral state of functional traits was reconstructed by Mesquite,and analyze the evolutionary process of functional traits.The following conclusions are drawn:(1)By reconstructing the phylogenetic tree of Stipa,the phylogenetic relationship of Stipa was determined.The results revealed that the species of Stipa were divided into two major clades.One clade was corresponded with Sect.Leiostipa,Sect.Smirnovia and Sect.Barbatae,while the other clade exactly matched majority species of Sect.Pseudoptilagrostis.Combining with morphological characteristics Stipa.roborowskyi was independently divided into Sect.Przewlsyiana.(2)There were significant differences in 10 functional traits between the grassland sub-region of central Asia and the alpine grassland sub-region of Qinghai-Tibet(P < 0.05),indicating that the Stipa was influenced by its habitats in the process of differentiation and development,and evolved different functional traits due to divergent evolution.(3)There are strong phylogenetic signals(K > 1)for the six traits of Stipa,including glume shape,hairy cover on leaves,flowering and fruit stage,lemma length,first awn column length and Awn Needle length,which indicates that these traits are strongly influenced by phylogenetic history.(4)The reconstruction of ancestral status showed that the ancestral status of this trait was lanceolate,which evolved into narrow lanceolate shape different from the ancestral status in the course of evolution.The ancestral status of other traits was not clear.These traits differentiated into many phenotypic traits in the later stage,indicating that most of the functional traits of Stipa species tended to evolve differently.In the evolution of functional traits,similar traits are almost clustered into one branch,which indicates that these traits are still in the stage of continuous evolution and are affected by both phylogenetic and environmental factors.To sum up,the Bayesian tree constructed from the four chloroplast gene sequences of Stipa is basically the same as the maximum likelihood tree.Stipa plants are divided into two major clades.One clade was corresponded with Sect.Leiostipa,Sect.Smirnovia and Sect.Barbatae,while the other clade exactly matched majority species of Sect.Pseudoptilagrostis.At the same time,through the study of the evolution history of functional traits of Stipa plants,it was found that most of the functional traits of Stipa plants chose to divergeand evolve,and their changes were the result of the interaction of environment and phylogeny.