DNA Barcoding Provides Taxonomic Clues for Identifying Five Endangered Phoebe Species in Southern China

Trees in the genus <i>Phoebe</i> of the Lauraceae family are commonly known as "Nanmu" in traditional Chinese culture. As they have offered highly valued timbers for construction, furniture, and coffins since the pre-Qin Dynasty, it is crucial to identify and protect these <i>Phoebe</i> species. However, the accuracy of <i>Phoebe</i> species identification is frequently hampered due to the limitations of traditional morphological and wood anatomy methods as the marker characteristics are very similar between the species, alongside the requirement for specialized expertise. Here, we use DNA barcoding technology for the rapid and accurate identification of five endangered <i>Phoebe</i> species in China, including <i>Phoebe bournei</i>, <i>P. chekiangensis</i>, <i>P. hui</i>, <i>P. sheareri</i> and <i>P. zhennan</i>. Four highly divergent regions (<i>petA</i>-<i>psbJ-psbL-psbF-psbE</i>, Ψ<i>ycf1-ndhF</i>, <i>rpl32</i>-<i>trnL</i>^UAG and <i>ycf1</i>) were identified from a comparison of the 20 <i>Phoebe</i> plastomes downloaded from the database. Furthermore, phylogenetic analysis on 20 <i>Phoebe</i> species showed that <i>rpl32-trnL^UAG</i> + <i>ycf1</i>, as well as <i>rpl32-trnL^UAG</i> + <i>ycf1</i> + Ψ<i>ycf1-ndhF</i>, effectively distinguished the fifteen <i>Phoebe</i> species. We further validated the usefulness of the core 2-locus barcode using wood and leaf samples from multiple sites for five target species. The study confirms the reliability of molecular diagnostics for five <i>Phoebe</i> species. It also establishes critical taxonomic protocols for conserving these endangered Nanmu species in southern China.