Abstract: The genus Didymocarpus Wall is a core group of the subfamily Didymocarpoideae in Gesneriaceae with a complex taxonomic history. It has long been controversial to delimit Didymocarpus and its allies. We conducted phylogenetic reconstructions with high-density sampling of Didymocarpus and related genera by using four nuclear ribosomal DNAs (ETS, ITS, 18S, 26S) and five chloroplast DNAs (atpB-rbcL, rpl16, rps16, trnH-psbA, trnL-F). The results demonstrate that both Didymocarpus and Allocheilos are not monophyletic. Based on molecular phylogenetic and morphological analyses, we delimitate the range of the Didymocarpus s. str. with two-section division, and established a new genus Palmatiboea for species originally placed in Didymocarpus. This genus is remarkably distinguished from Didymocarpus s. str. not only in molecular phylogeny and morphology but also in its specific geographic distribution that are found only in the southeastern China. In addition, we also proposed a new monotypic genus Hequnia for Allocheilos guangxiensis that is completely isolated in phylogeny, consistent with a range of remarkably distinctive morphological characteristics. Our results clarify the systematics of Didymocarpus and the delimitation between it and related genera with establishment of two new genera.

Key words: Didymocarpus, Gyrocheilos, Petrocodon, Allocheilos, phylogenetic reconstruction, taxonomic treatment