Abstract
Three new species of Polycarpaea from Vietnam, Polycarpaea vanphongensis V.T. Tran, H.T. Truong & N.V. Binh, Polycarpaea chungana V.T. Tran, H.T. Truong & N.V. Binh, Polycarpaea phuquocensis V.T. Tran, H.T. Truong & N.V. Binh are described and illustrated based on evidence of molecular sequence data from two markers (ITS1-5.8S-ITS2 and rps16) and combined morphological characteristics. Polycarpaea vanphongensis is closely related to Polycarpaea gaudichaudi Gagnep., Polycarpaea arenaria (Lour.) Gagnep., Polycarpaea phuquocensis V.T. Tran, H.T. Truong & N.V. Binh but differs by its stem glabrous, leaf ovate to elliptic, glabrous, ovary oblong ovoid, base obtuse, apex attenuate, capsule oblong void, 3.8 mm long. Polycarpaea phuquocensis V.T. Tran, H.T. Truong & N.V. Binh differs from the three species mentioned above by its stem being densely villous, leaf spathulate, ciliate, ovary ovoid, base acute, apex obtuse, capsule ovoid, 1.2 mm long. Polycarpaea chungana V.T. Tran, H.T. Truong & N.V. Binh is most similar to Polycarpaea lignosa Gagnep., but differs in having leaf oblong or linear, sparse ciliate, sepal and petal apex deeply concaved or slightly bifid, ovary ovoid, ovoid, 0.8-1.0 mm long. Furthermore, the achievements of analysis using molecular data on the systematic positions of 7 other species are results that have not been in previous molecular analyses.