The first phylogenetic hypothesis for the southern African endemic genusTulbaghia(Amaryllidaceae, Allioideae) based on plastid and nuclear DNA sequences

Abstract

Southern Africa has three indigenous genera in the Amaryllidaceae subfamily Allioideae. Prototulbaghia is monospecific and Allium is represented by a single species, whereas Tulbaghia has > 20 described species. Tulbaghia spp. are popular in horticulture and used extensively as medicinal plants in southern Africa. Despite their popularity and economic importance, species delimitation is problematic and the infrageneric classification uncertain. The objective of this study was to test the monophyly of Tulbaghia and the relationships of Prototulbaghia and to produce the first molecular phylogenetic hypothesis for Tulbaghia as a basis for a revised infrageneric classification and species concepts. Fifty-four Tulbaghia samples covering 17 of the c. 23 accepted species were included in this study. In total, 160 new sequences of nuclear ribosomal internal transcribed spacers (ITS) and plastid encoded trnL-F and ndhF were produced for this study and were analysed using maximum parsimony and Bayesian inference. Tulbaghia including Prototulbaghia is strongly supported as monophyletic (BP = 100%, PP = 1.00) and in general clades that are well supported in either or both of the ITS and the combined plastid analysis are also well supported in the total combined analysis. Several major clades within Tulbaghia are resolved and ITS and plastid data indicated that Prototulbaghia and some Tulbaghia spp. are in need of taxonomic recircumscription.