Systematics of Tribe Oncobeae (Salicaceae/ Achariaceae/ Flacourtiaceae)
Caloncoba gilgiana. Photo: H. Beentje.
Hul & Breteler (1997) and Chase et al. (2002) proposed different systems of classification and nomenclature for a group of genera within Oncobeae, a tribe of mostly African tropical trees and shrubs traditionally placed within Flacourtiaceae. Hul and Breteler (1997) used morphological characters, Chase et al. (2002) mainly DNA sequence data with supporting morphological and phytochemical evidence. Both concepts are being adopted by different user groups, causing taxonomic confusion. The purpose of the current project is to reconcile this conflict.
Hul & Breteler (1997) reduced five genera (c. 30 species) of Oncobeae to synonymy of Oncoba, a genus that previously included only three to four species. Field specialists support the Hul & Breteler revision, finding that it agrees well with their own experience of the group. In Chase et al. (2002) approximately two-thirds of all Flacourtiaceae genera were transferred to Salicaceae, and the remaining one-third to Achariaceae. Surprisingly, Oncoba sensu Hul & Breteler split across both families, despite the apparent similarity among its species. Oncoba spinosa became nested within Salicaceae while all other sampled Oncoba species fell into Achariaceae. The split has taxonomic implications. Oncoba spinosa is the type of the genus; its transfer to Salicaceae means that the Oncoba species of Achariaceae need a new generic name.
The objective of this project is to take a fresh and more detailed look at the morphology and molecular systematics of tribe Oncobeae, including sampling DNA sequence data for all species. The synonymy proposed by Hul & Breteler will be reassessed and nomenclatural changes made if necessary. The primary product will be either a revised taxonomic treatment for the group, or an amendment to the phylogenetic study of Chase et al. In either case the position of Oncoba spinosa will be clarified. An additional output will be the revised character data; this will contribute to the Malpighiales Interactive Key (see Interactive Key to the Genera of Malpighiales). Project duration is expected to be two years.
Project Team
Project Leader: Zmarzty, Sue
Herbarium
Sue Zmarzty
Jodrell Laboratory
Mark Chase
Project Partners and Collaborators
The Netherlands
National Herbarium of the Netherlands, Wageningen University branch.