Molecular phylogenetic analysis and generic delimitations in tribe Chiococceae (Cinchonoideae, Rubiaceae)

Abstract

Tribe Chiococceae (Cinchonoideae, Rubiaceae) are morphologically diverse, ranging from subshrubs, erect or scandent shrubs, vines, treelets to tall trees, with an extreme variation in shape and size of corolla and several fruit types. The tribe also exhibits a case of amphi-Pacific distribution. Although previous studies have established the monophyly of the tribe, which is confirmed here, intergeneric and intrageneric relationships in Chiococceae were not well-resolved. This study presents the most comprehensive molecular phylogenetic study to date, including 27 genera and 125 species. Taxonomic affinities and evolutionary relationships discussed in this study are based on the phylogenetic tree generated by analysing molecular sequence data of two nuclear (ETS, ITS) and two plastid (petD, trnL-F) regions using Bayesian and maximum likelihood methods. Based on the present results, 30 genera are recognized in Chiococceae. Adolphoduckea, Coutareopsis, Motleyothamnus and Ramonadoxa are newly described. Ceuthocarpus, Morierina and Phyllacanthus are synonymized under Schmidtottia, Thiollierea and Catesbaea, respectively. Catesbaea, Salzmannia, Schmidtottia, Solenandra and Thiollierea are re-circumscribed. Nineteen new combinations are proposed.