Phylogenetic Relationship Analysis Based on ITS Sequences and Morphological Characteristics for Betula Species in Xinjiang

Six species of Betula Linn. in Xinjiang and 10 other species of Betula Linn. were further studied. Internal transcribed spacer (ITS) gene were used to compare and analyze phylogenetic trees with Cluster Omega and MEGA 7.0 software. Meanwhile, principal component analysis and cluster analysis of were carried out by using SPSS 25.0 software based on 7 morphological traits. The results revealed that phylogenetic trees of ITS indicated the genetic distance between betula and subsect. Fruticosae was 0.0047, and the absolute genetic distance within Xinjiang Betula species was 0.0060. In the principal component analysis of morphological traits, the cumulative contribution rate of eigen value greater than 1 was 84.5%. The taxonomic characters of Betula mainly depended on life form, leaf shape, back coat of fruit bud, bark dehiscence and grain. Betula halophila and Betula humilis are clustered together in the respect of molecule, which is different from the classification of B. halophila and B. humilis in flora of China, but similar to the conclusion that B. halophila and B. humilis belong to the same subgroup in flora of Xinjiang.