Abstract
Two new species of Polyalthiopsis (Annonaceae), P. nigra Y.H. Tan & Bin Yang from Guangxi and Yunnan Provinces and P. xui Y.H. Tan & Bin Yang from Yunnan Province, are described and illustrated. P. nigra is morphologically similar to P. chinensis in having narrowly elliptic-oblong, lemon to yellowish green petals, but differs by having obovoid monocarps, a higher number of leaf secondary veins, leaf blades usually widest above the middle, and a lower ratio of leaf blade length to width. P. xui is morphologically similar to P. floribunda in having axillary inflorescences, 1-3(-4) flowers, elliptic leaves, and elliptic-ovate petals, but differs in the numbers of carpels per flower and ovules per carpel. The molecular phylogenetic analysis using five plastid markers confirm that the two new species belong to the genus Polyalthiopsis and show clear interspecific divergences between P. nigra and P. xui and between them and other species in the genus. Detailed descriptions, colored photographs, and habitat and distribution data for the two new species are provided. In addition, the fruit morphology of P. chinensis is described for the first time, based on living collections. Geographical distributions and a diagnostic key for all Polyalthiopsis species are also presented.