| In order to understand the genetic relationship of 6 species of Juniperus and their adaptability to cold and drought environment on the Plateau,this study constructed the phylogenetic tree of 6 Juniperus species by the needle structure.6 Juniperus species were Juniperus przewalskii,J.tibetica,J.convallium,J.sabina,J.komarovii and J.formosana from Qinghai province.This study revealed their systematic relationship.This paper also studied the change of the need structures of J.przewalskii and J.tibetica on the altitude gradient,discussed the similarities and differences of their ecological adaptability,and explained the systematic relationship from the perspective of ecological adaptability.This study provides anatomical evidence for the phylogeny of 6 Juniperus species.It also provides reference for the division and amalgamation of Juniper and Sabina.The main results are as follows:(1)There were significant differences in 20 needle structures among 6 Juniperus species.According to the similarity matrix and cluster analysis results,the difference of needle structures between J.tibetica and J.convallium was the smallest,followed by J.przewalskii and J.komarovii.The difference of needle structure between J.formosana and other 5 Juniperus species was great,followed by J.sabina.Correlation analysis showed that 16 coniferous structures were correlated among interspecific changes,while epidermal cell width,palisade cell length,stomatal apparatus distance and vascular bundle xylem/phloem had no correlation with other structures,and their consistency index(CI)and phylogenetic signal K values were low.(2)The results showed that the phylogenetic tree constructed by the extremum method was the most consistent with the minimalism principle,and had a higher consistency index CI=0.797,while that of the deviation method was CI=0.745.(3)The results of cladism showed that J.tibetica was closely related to J.convallium,J.przewalskii was closely related to J.komarovii,J.formosana was relatively distant from other Juniperus species,followed by J.sabina.(4)J.przewalskii adapted to the climate conditions at high altitude by thickening leaf width,palisade cell length/width,and reducing stomatal size;J.tibetica adapted to the climate conditions at high altitude by increasing leaf width,leaf thickness,cuticle thickness,epidermal cell thickness,stomatal size and stomatal distance.These structures have abundant phylogenetic signals,indicating that the differentiation of Juniperus is related to the different ecological adaptation strategies of different species. |
