Phylogeny of Bonatea (Orchidaceae: Habenariinae) based on molecular and morphological data

Abstract

The genus Bonatea is widely distributed throughout southern and eastern Africa. Considerable debate surrounds the generic status of Bonatea, but there have been neither previous studies of evolutionary relationships among Bonatea species, nor any tests of the monophyly of the genus in relation to its close relative Habenaria. We investigated phylogenetic relationships between Bonatea and selected Habenaria species using morphology, as well as sequences of the chloroplast gene matK and the internal transcribed spacer (ITS) regions of nuclear ribosomal DNA. A fully resolved cladogram was obtained using morphological data, but neither the ITS, matK, nor combined data sets yielded well-resolved and well-supported phylogenetic structure for Bonatea. There is poor congruence between ITS and matK data for interspecific relationships in Bonatea, whilst the morphological results are largely congruent with the ITS analysis. Relative to Habenaria, there is little sequence variation between Bonatea species, which could indicate a recent and rapid radiation of Bonatea. Although the sampled Bonatea species form a distinct clade, more extensive sampling of Habenaria would be required to establish unambiguously whether or not Bonatea is monophyletic.