Abstract
Pteronia L. is a large genus of woody perennials with more than 70 species. The genus is largely restricted to southern Africa with one species in Zambia. The last taxonomic treatment of Pteronia was published in 1917 by J. Hutchinson and E. P. Phillips and since then, the genus has not been revised. In South Africa, where most of the species occur, the genus has been identified as one of the top priority genera for taxonomic research. The taxa are poorly known in terms of their distribution and morphological variation within and among species, several taxa are undescribed and little is known concerning the evolutionary relationships of the genus and its constituent species.
The current study employed a multidisciplinary approach to assess the southern African Pteronia species in order to investigate their phylogenetic relationships, biogeography, divergence times as well as to review their taxonomy using molecular (DNA sequences), morphological, anatomical and biogeographical data. Phylogenetic relationships were investigated using parsimony, Bayesian inference and maximum likelihood analyses of two nuclear (ITS & ETS) regions and one plastid (trnL-F) region. The estimation of divergence ages was carried out using a Bayesian relaxed clock method implemented in BEAST and the ancestral distribution of the genus was investigated using Lagrange and S-Diva, implemented in RASP.
Morphological and anatomical studies revealed variation in characters such as leaf size, shape and vestiture, capitula shape, involucre shape, pappus series, cypselae shape, size and vestiture, presence or absence and type of trichomes, number of vascular bundles, type of secretory structure in the mesophyll, epidermal glands, epidermal cell shape in the leaves and cypselae (in transverse section – TS) as well as the number of ribs and type of cells associated with vascular bundles at the ribs in...
Ph.D. (Botany)