Hedyotiskonhanungensis (Rubiaceae): A new species from the central highlands of Vietnam.

A new species of Hedyotis L. (Rubiaceae), Hedyotiskonhanungensis B.H. Quang, T.A. Le, K.S. Nguyen & Neupane, is described and illustrated from the central highlands of Vietnam based on morphological and phylogenetic evidence. The new species belongs to the morphologically diverse tribe Spermacoceae (ca. 1000 species) of the family Rubiaceae, which is represented by 70-80 species in Vietnam. The phylogenetic analysis, based on four DNA regions (ITS, ETS, petD, rps 16), confirms the new species' placement within the genus Hedyotis - one of the largest genera in the tribe, comprising ca. 180 species across Asia and the Pacific. Hedyotiskonhanungensis is morphologically distinct from all southeastern Asian Hedyotis L. in its set of traits such as leaf type (shape and thickness), growth habit, and floral parts (color of inflorescence axis and the shape of calyx lobes). The new species shows similarities with Hedyotisshenzhenensis , H.shiuyingiae , and H.yangchunensis from China in its herbaceous habit, fleshy ovate leaf blades, and dark purple floral parts, but it is phylogenetically distinct and can be distinguished from them by the following combination of morphological traits: habit with slightly smaller stature (<25 cm), broadly ovate or deltoid stipules with cuspidate apex and entire margin, and ovate or nearly ovate calyx lobes.