Morphological and Molecular Evidence for a New Species Within Styrax (Styracaceae) from a 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. This new species seems somewhat similar to Styrax fortunei, but significantly differs from it by having long ovate or long lanceolate leaves, often with an asymmetrical base (vs. obovate-elliptic to elliptic, often with a symmetrical base) and fertile shoots with fewer flowers (1, or rarely 2 or 3, vs. many, always more than 10). Phylogenetic analyses based on the chloroplast coding sequences indicated that S. chongzuoensis and Styrax japonicus are sister taxa to each other, both clustered in the series Cyrta within Styrax. Overall, the integration of morphological and phylogenetic evidence indicates that S. chongzuoensis actually represents a new species. Color plates of S. chongzuoensis are illustrated, and a distribution map and conservation assessment of this species are also provided.