Comparative Analysis of Complete Chloroplast Genome Sequences in (Thymelaeaceae) and New Insights Into Phylogenetic Relationships.

The complete chloroplast genomes of three species of namely, , , and (Thymelaeaceae), are reported and characterized. The chloroplast genomes displayed a typical quadripartite structure with conserved genome arrangement and specific divergence. The genomes ranged in length from 172,708 to 173,621 bp and displayed similar GC content of 36.5-36.7%. A total of 138-139 genes were predicted, including 92-93 protein-coding, 38 tRNAs and eight rRNAs genes. Variation in the number of short simple repeats and inverted region boundaries of the three cp genomes were observed. A mutational hotspot was detected along the nucleotide sequence from the F to the L-UAG genes. The chloroplast genome-based and internal transcribed spacer (ITS)-based phylogenetic analyses using maximum-likelihood (ML) and Bayesian inference (BI) revealed that diverged before and and placed the clade at the base of the Eurasian Daphne group with strong bootstrap support. With an effective taxonomic treatment of the species of , further molecular analyses of their intra- and interspecific genetic variation are inclined to support the treatment of and as two natural groups. The genetic information obtained from this study will provide valuable genomic resources for the identification of additional species and for deducing the phylogenetic evolution of .