Dealing with dissention in the ranks: A phylogenetic study of Odontadenieae (Apocynaceae)

The circumscription of Odontadenieae (Apocynaceae) and its constituent genera (including the infrageneric classifications for Odontadenia) are tested here based on the phylogenetic analyses of 33 nuclear and 164 chloroplast sequences from 33 species, 84 available for the first time. As currently circumscribed, Odontadenieae is monophyletic, with the genera divided into three main clades. However, Odontadenia and the subgenera and sections of its three earlier infrageneric classifications are all non‐monophyletic. Secondatia is nested within Odontadenia, and O. laxiflora is nested in Pentalinoninae. In order to achieve a monophyletic Odontadenia, we propose the recognition of Codonechites and its transfer to Pentalinoninae. Secondatia species are transferred to Odontadenia, and Angadenia is reduced to a synonym of Pentalinon. Our results support the inclusion of Elytropus in Mesechiteae and the recognition of three sections in Odontadenia. The status of O. sect. Anomalae cannot be evaluated at this time, and is treated as incertae sedis. Eight genera and 39 species are recognized in the tribe here. In addition to the previously published Pentalinoninae, two new subtribes, Cycladeniinae and Odontadeniinae, are published here to accommodate the taxa in the corresponding clades recovered in this study.