Towards a better understanding of intertribal relationships and stable tribal delimitations within Cinchonoideae s.s. (Rubiaceae)

Abstract

This study focuses on the subfamily Cinchonoideae s.s. utilizing information from six DNA markers and 206 taxa. The nine tribes (i.e. Cinchoneae, Chiococceae s.l., Guettardeae s.s., Hamelieae, Hillieae, Hymenodictyeae, Isertieae, Naucleeae s.l., and Rondeletieae s.s.) are resolved in four major lineages, all strongly supported and relationships between them are resolved. The tropical American Cinchoneae and Isertieae constitute the first diverging lineage within the subfamily, followed by the predominantly paleotropical Naucleeae and Hymenodictyeae. The remaining two lineages primarily include neotropical taxa: Rondeletieae and Guettardeae are sister clades in the first, while the second comprises Chiococceae, Hamelieae, and Hillieae. Additionally, taxonomic placement of several genera, not previously included in molecular analyses, were confirmed: Acunaeanthus belongs in Rondeletieae, Ottoschmidtia in Guettardeae, Nernstia in Chiococceae, Pinarophyllon, Plocaniophyllon, and Syringantha in Hamelieae, and Balmea in Hillieae. Colleteria, of previously unknown taxonomic position, is resolved as sister to Chione.