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Comparison of Chloroplast Genomes and Phylogenetic Analysis of Four Species in Quercus section Cyclobalanopsis
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  • Xiaoli Chen,
  • Buyu Li,
  • Ting Huang,
  • Xuemei Zhang
Xiaoli Chen
China West Normal University
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Buyu Li
China West Normal University
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Ting Huang
China West Normal University
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Xuemei Zhang
China West Normal University

Corresponding Author:[email protected]

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Abstract

The identification in Quercus L. species was considered to be difficult all the time. The fundamental phylogenies of Quercus have already been discussed by morphological and molecular means. However, the morphological characteristics of some Quercus groups may not be consistent with the molecular results (such as the group Helferiana ), which may lead to blurring of species relationships and prevent further evolutionary researches. To understand the interspecific relationships and phylogenetic positions, we sequenced and assembled the CPGs (160715 bp ~ 160842 bp) of four Quercus section Cyclobalanopsis species by Illumina pair-end sequencing. The genomic structure, GC content and IR/SC boundaries exhibited significant conservatism. Six highly variable hotspots were detected in comparison analysis, among which rpoC1, clpP and ycf1 could be used as molecular markers. Besides, two genes (petA, ycf2) were detected to be under positive selection pressure. The phylogenetic analysis showed: Trigonobalanus genus and Fagus genus located at the base of the phylogeny tree; the Quercus genus were distincted to two clades, including five sections. All CTB species clustered into a single branch, which was in accordance with the results of the morphological studies. But neither of group Gilva nor group Helferiana had formed a monophyly. Six CTB species gathered together in pairs to form one branch respectively (Quercus kerrii and Quercus chungii; Quercus austrocochinchinensis with Quercus gilva; Quercus helferiana and Quercus rex). Due to a low support rate (0.338) in the phylogeny tree, the interspecies relationship between the two branches differentiated by this node remained unclear. We believe that Q. helferiana and Q. kerrii can exist as independent species due to their distance in the phylogeny tree. Our study provided genetic information in Quercus genus, which could be applied to further studies in taxology and phylogenetics.