Integrating phylogenomic and morphological evidence to solve the taxonomy of Phoebe legendrei (Lauraceae) and closely related species.

BACKGROUND: The genus Phoebe, belonging to the tribe Perseeae of the Lauraceae, is well known for its important economic value and the need for its conservation. However, the taxonomic delimitation of species remains poorly resolved due to complicated morphological variation in Phoebe, thus hindering conservation efforts and resource utilization. Here we sequenced 18 samples of the genus, reconstructed new plastome phylogenomic trees of Phoebe from East Asia with special emphasis on Phoebe legendrei and its closely related species. We also conducted comparative analyses of both plastomes and morphology between P. legendrei and its closely related species, and examined the protologue and the type collection of P. legendrei, and conducted a taxonomic treatment. RESULTS: Our comparative genomic analysis confirmed that plastomes of the genus Phoebe are relatively conservative, but P. legendrei 94 differs from P. legendrei 143 in number of dispersed repeats, IR boundary, and highly variable regions. The newly reconstructed phylogenomic trees are robustly supported, with Phoebe species divided into three major clades. Phoebe crassipedicella is sister to P. kwangsiensis, but the eight samples of P. legendrei formed two separate subclades (represented by P. legendrei 94 differs from P. legendrei 143, respectively). We conducted a morphological study and revealed that the two subclades differed in perianth lobe size, fruiting pedicel length, and the clasping status of the persistent perianth lobes. We examined the protologue and morphology of the type collection of P. legendrei, and determined a new species, i.e., Phoebe panzhihuaensis sp. nov. CONCLUSIONS: In this study, we resolved the taxonomic delimitation within P. legendrei and its closely related species, and discovered a new species of Phoebe from southwestern China. This work contributes to evaluating species diversity within Phoebe and lays the foundation for the conservation and resource utilization of these species.