Morphological and Molecular Evidence for a New Species Within <em>Styrax</em> (Styracaceae) from Karst Area in Southwest Guangxi, China

Styrax chongzuoensis, a novel endemic species with a narrow distribution in limestone regions of Chongzuo, Guangxi, China, is described herein. Careful comparison of this species with all other Styrax species in China, as well as those in adjacent Vietnam, shown that it is essentially different, and is somewhat similar to S. argentifolius in leaf morphology, but significant differences exist due to its habit (deciduous shrubs vs. evergreen trees), thickly chartaceous (vs. coriaceous) leaf blade, inflorescence shape, and flowers number. To further ascertain the taxonomic position of S. chongzuoensis, we sequenced and assembled its plastomes. Notably, phylogenetic analyses based on the complete chloroplast genome clarify the taxonomic position of S. chongzuoensis in Styrax. Overall, the integration of morphological and phylogenetic evidence indicates that S. chongzuoensis actually represents a new species. Colour plates of S. chongzuoensis was illustrated, a distribution map and conservation assessment of this species were also provided.