Phylogeny of Southern African and Australasian Wahlenbergioids (Campanulaceae) based on ITS and trnL-F sequence data: implications for a reclassification

Abstract

The Campanulaceae: Wahlenbergioideae currently comprises 15 genera, one of which, Wahlenbergia, is widespread over the southern continents. Southern Africa is the region with maximum wahlenbergioid diversity with 12 genera and approximately 252 species. A second center is Australasia with 38 Wahlenbergia species. This study used a broad sample of wahlenbergioid diversity from South Africa, Australia, and New Zealand to reconstruct a phylogeny based on chloroplast trnL-F and nuclear ITS sequences. Data were analyzed separately and in combination using parsimony and Bayesian methods. The results suggest that for the wahlenbergioids to be monophyletic Wahlenbergia hederacea has to be excluded and that none of the South African, Australian or New Zealand lineages are strictly monophyletic. There are five species assemblages that are in some disagreement with current classification in the family. Wahlenbergia, Prismatocarpus and Roella are shown to be non-monophyletic and implications for a reclassification are presented. Careful consideration of morphological characters is suggested before the adjustment of generic circumscriptions can be accomplished.