Jacques Florence

Paraphyly of Ixora and new tribal delimitation of Ixoreae (Rubiaceae): Inference from combined chloroplast (rps16, rbcL and trnT-F) sequence data

Abstract We performed phylogenetic analyses of DNA sequences of three chloroplast markers: rbcL, rps16, and trnT-F, to rigorously test the monophyly of competing circumscriptions of the tribe Ixoreae. Several genera traditionally or currently associated with the type genus Ixora L. were included in the analyses. Ixora as currently circumscribed appears paraphyletic, as many other genera are nested within it with strong support: Captaincookia N. Hallé, Doricera Verdc., Hitoa Nadeaud, Myonima Comm. ex Juss., Sideroxyloides Jacq., Thouarsiora Homolle ex Arènes, and Versteegia Valeton. Further, Aleisanthia Ridl., Aleisanthiopsis Tange, and Greenea Wight & Arn. are more closely related to Ixora and allies than the monotypic genus Scyphiphora C. F. Gaertn. Consequently, Ixoreae fide Andreasen and Bremer (2000) is not monophyletic without an exclusion of Scyphiphora. Ixoreae fide Robbrecht and Manen (2006) is not monophyletic unless Captaincookia and Doricera are included. The monophyly of a morphologically heterogeneous Ixoreae alliance consisting of Ixora and its relatives Aleisanthia, Aleisanthiopsis, and Greenea is, however, strongly supported. In order to recognize monophyletic and morphologically consistent groups, we adopt a narrow circumscription of Ixoreae (including Bemsetia Raf., Captaincookia, Charpentiera Vieill., Doricera, Hitoa, Ixora, Myonima, Pancheria Montrouz., Sideroxyloides, Thouarsiora, Tsiangia But, H. H. Hsue & P. T. Li, and Versteegia), and two new tribes are erected for Aleisanthia + Aleisanthiopsis and Greenea, respectively. The Indo-Malesian Aleisanthieae and the pantropical Ixoreae s. str. are sister groups, and the Southeast Asian Greeneeae is sister to the Ixoreae–Aleisanthieae clade.