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

<i>Styrax chongzuoensis</i>, 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 <i>Styrax fortunei</i>, 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 <i>S. chongzuoensis</i> and <i>Styrax japonicus</i> are sister taxa to each other, both clustered in the series <i>Cyrta</i> within <i>Styrax</i>. Overall, the integration of morphological and phylogenetic evidence indicates that <i>S. chongzuoensis</i> actually represents a new species. Color plates of <i>S. chongzuoensis</i> are illustrated, and a distribution map and conservation assessment of this species are also provided.