Characterization of the Complete Chloroplast Genome and Evolutionary Position of Clematis tomentella

Clematis tomentella 2001 (Ranunculaceae) is a typical drought-tolerant sand-fixing plant in desert ecosystem in northwest China. To elucidate the phylogenetic status of C. tomentella and its related species, we determined the complete chloroplast (cp) genome and analyzed their interspecific relationships. The result showed that the cp genome of C. tomentella was 159 816 bp in length, including two inverted repeats of 31 045 bp, a large single copy region of 79 535 bp, and a small single copy region of 18 191 bp. 136 genes were annotated across the whole cp genome, including 92 protein-coding genes, 8 rRNA genes, and 36 tRNA genes, as well as the GC content accounted for 38%. Crucially, we found that the regions of psbE-petL, trnG_UCC-atpA, ndhF-rpl32, and rps8-infA were highly divergent, which could be marked as DNA barcodes for the identification of C. tomentella in Ranunculaceae. A maximum likelihood phylogenetic tree revealed that C. tomentella was closely related to C. fruticosa. Our results provide the references and implications for the phylogenetic study of Clematis in Ranunculaceae in the future.