10Castanopsis sclerophylla (Lindl.) Schott is an important species of evergreen broad-leaved forest in 11 subtropical area and has important ecological and economic value. However, there are little studies on its 12 chloroplast genome. In this study, the complete chloroplast genome sequences of C. sclerophylla was reported 13 based on the Illumina Hiseq 2500 platform. The complete chloroplast genome of C. sclerophylla was 14 160,497bp, including a pair of inverted repeated (IRs) regions (25,675bp) that were separated by a large single 15 copy (LSC) region of 90,255bp, and a small single copy (SSC) region of 18,892bp. The overall GC content of 16 chloroplast genome was 36.82%. A total of 131 genes were found, of these 111 genes were unique and 17 annotated, including 79 protein-coding genes, 27 transfer RNA genes (tRNAs), and four ribosomal RNA genes 18 (rRNAs). Twenty-one genes were found to be duplicated in the IR regions. Comparative analysis indicated that 19 IR contraction might be the reason for the relatively smaller chloroplast genome size of C. sclerophylla 20 compared with other three congeneric species. Sequence analysis detected that the LSC and SSC regions were 21 more divergent than the IR regions within the Castanopsis, furthermore, a higher divergence was found in non-22 coding regions than in coding regions. The maximum likelihood (ML) phylogenetic analysis showed that these 23 four species of the genus Castanopsis formed a monophyletic clade and that C. sclerophylla is closely related 24 to Castanopsis hainanensis with strong bootstrap values. These results not only provide basic knowledge about 25 characteristics of C. sclerophylla and also enhance our understanding of Castanopsis species evolution within 26 the Fagaceae family. Meanwhile, these findings will contribute to the exploration, utilization and conservation 27 genetics of C. sclerophylla.28 Keywords: Castanopsis sclerophylla; chloroplast genome; comparative analysis; phylogenetic analysis 29 30 Introduction 31 Castanopsis sclerophylla (Lindl.) Schott. is a monoecious, and broad-leaved tree of the genus 32 Castanopsis belongs to the Fagaceae family. The genus contains about 120 known species, of these species 33 58 are native to China, and 30 are endemic. However, this species is widely native to East and South 34 Asia, and had been introduced to North America [1, 2]. In China, it is a canopy tree widely distributed 35 in subtropical evergreen forests [3]. Its fruit and wood are valuable, and are regarded as landscape 36 and ornamental tree because of glossy evergreen leaves and white flowers cover the tree [4]. In Jiangxi 37 province, its fruit has been used to make special foods such as sheet jelly, bean curd, and bean 38 vermicelli [5]. The previous researches mainly focused on natural regeneration[6], biomass[7], 39 morphology[8], chemotaxonomical[9], genetic diversity [1, 10]. Currently, because of the tree's 40 economic value increasing, natural plants have been seriously destroyed by humans, and the number 41 of natural trees is...