Systematics of Bonatea (Orchidaceae) : species boundaries and phylogeny.

Thesis (M.Sc.)-University of KwaZulu-Natal, 2006.Bonatea Willd. (Orchidaceae: Habernariinae) is a small genus confined to the African continent and Arabia. Phylogenetic and morphometric analyses were undertaken in order to evaluate phylogenetic relationships and species delimitations within Bonatea. In the phylogenetic analyses, little congruence was found between ITS and matK molecular data, while morphological results were largely congruent with those of the ITS region. There is little sequence variation within and between Bonatea species, which could indicate a recent and rapid radiation. The generic characters for Bonatea were reevaluated. Bonatea is closely related to Habenaria but differs in having a galeate middle rostellum lobe that is clearly separated from the vertical anther thecae. By contrast, species of Habenaria have short anthers that are slightly arcuate and flank the rostellum. Morphometric analyses were used to determine taxon boundaries within the Bonatea speciosa and Bonatea cassidea complexes, respectively. Principle component and cluster analyses of morphological variation support the recognition of Bonatea antennifera Rolfe, Bonatea boltonii (Harv.) Bolus and Bonatea speciosa (L.f.) Willd. as distinct species. Morphological evidence supports the inclusion of Bonatea porrecta (Bolus) Summerh. and Bonatea volkensiana (Kraenzl.) Rolfe in the B. speciosa c1ade and this is corroborated by molecular data for the former. Clinal variation in petal lobe dimensions and colour across the distribution range of Bonatea cassidea Sond. encompasses the taxon Bonatea saundersiae (Harv.) T.Durand & Schinz, which is reduced to synonymy. Bonatea saundersioides (Kraenzl. & Schltr.) Cortesi, the sister species to B. cassidea, also exhibits colour variation in its petals. A revision of Bonatea is presented recognizing 14 species. Bonatea eminii (Kraenzl.) Rolfe was excluded due to insufficient information. Full descriptions are provided with diagnostic characters and distributional maps. Bonatea bracteata G.McDonald & McMurtry and Bonatea tentaculifera Summerh. are removed from Bonatea based on their rostellum structure which is inconsistent with the revised generic concept. Bonatea bracteata was transferred as Habenaria transvaalensis Schltr. and B. tentaculifera was renamed Habenaria bonateoides M.Ponsie, as the specific epithet is currently occupied within Habenaria