From Polyalthia to Polyalthiopsis (Annonaceae): transfer of species enlarges a previously monotypic genus

The genus Polyalthiopsis Chaowasku (Annonaceae) was a poorly known monotypic genus from Vietnam that was recently segregated from the highly polyphyletic genus Polyalthia s.l. The sister clade relationship between Polyalthiopsis and Miliusa was not well established in previous study. The phylogenetic position of two Polyalthia spp. from China, P. chinensis S.K.Wu ex P.T.Li and P. verrucipes C.Y.Wu ex P.T.Li, remains unresolved and is shown here to be phylogenetically affiliated with Polyalthiopsis. Phylogenetic analyses of six chloroplast regions (matK, ndhF, psbA-trnH, rbcL, trnL-F and ycf1; ca.7.3 kb, 60 accessions) unambiguously placed Polyalthia chinensis and P. verrucipes in the same clade with Polyalthiopsis floribunda (PP = 1, MPBS = 97%); the entire clade is sister to Miliusa with weak to strong support (PP = 1, MPBS = 54%). Polyalthia chinensis and P. verrucipes share several diagnostic characters with Polyalthiopsis floribunda, including the raised midrib on the upper surface of the leaf in vivo, conspicuous foliar glands when dried, petiole with transverse striations when dried and axillary inflorescences. The two species differ from Polyalthiopsis floribunda in having fewer flowers per inflorescence, longer linear petals and two ovules per carpel. On the basis of the combined molecular phylogenetic and morphological data, we propose two new combinations, Polyalthiopsis chinensis (S.K.Wu ex P.T.Li) B.Xue & Y.H.Tan and Polyalthiopsis verrucipes (C.Y.Wu ex P.T.Li) B.Xue & Y.H.Tan. The protologue of Polyalthia verrucipes did not include a description of the flowers, which we provide here. An updated description for the genus Polyalthiopsis and a key to species in the genus Polyalthiopsis is also provided.