Chloroplast Genome Evolution and Species Identification of Styrax (Styracaceae)

The genus Styrax L. consists of approximately 130 species distributed in the Americas, eastern Asia, and the Mediterranean region. The phylogeny and evolutionary history of this genus are not clear. Knowledge of the phylogenetic relationships and the method for species identification will be critical for the evolution of this genus. In this study, we sequenced the chloroplast genome of 17 Styrax samples and added 17 additional chloroplast genome sequences from GenBank. The data were used to investigate chloroplast genome evolution, infer phylogenetic relationships, and access the species identification rate within Styrax. The Styrax chloroplast genome contains typical quadripartite structures, ranging from 157,641 bp to 159,333 bp. The chloroplast genome contains 114 unique genes. The P distance among the Styrax species ranged from 0.0003 to 0.00611. Seventeen small inversions and SSR sites were discovered in the Styrax chloroplast genome. By comparing with the chloroplast genome sequences, six mutation hotspots were identified, and the markers ycf1b and trnT-trnL were identified as the best Styrax-specific DNA barcodes. The specific barcodes and superbarcode exhibited higher discriminatory power than universal barcodes. Chloroplast phylogenomic results improved the resolution of the phylogenetic relationships of Styrax compared to previous analyses.