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

Trees in the genus Phoebe 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 Phoebe species. However, the accuracy of Phoebe 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 Phoebe species in China, including Phoebe bournei, P. chekiangensis, P. hui, P. sheareri and P. zhennan. Four highly divergent regions (petA-psbJ-psbL-psbF-psbE, Ψycf1-ndhF, rpl32-trnL^UAG and ycf1) were identified from a comparison of the 20 Phoebe plastomes downloaded from the database. Furthermore, phylogenetic analysis on 20 Phoebe species showed that rpl32-trnL^UAG + ycf1, as well as rpl32-trnL^UAG + ycf1 + Ψycf1-ndhF, effectively distinguished the fifteen Phoebe 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 Phoebe species. It also establishes critical taxonomic protocols for conserving these endangered Nanmu species in southern China.