Based on analysis of vegetative and floral morphology, karyology and floral flavonoids, the genus Duvalia is revised. Seventeen species are recognized, one is described as new and three are reduced to infraspecific rank. All taxa are illustrated and distribution maps are provided. The species can be referred to two sections that match with the area of distribution: (1) sect. Duvalia, southern Africa, with D. angustiloba, D. caespitosa, D. corderyoi, D. elegans, D. gracilis, D. immaculata, D. maculata, D. modesta, D. parviflora, D. pillansii, D. polita, D. pubescens and D. vestita, and (2) sect. Arabica, NE Africa and SW Arabian Peninsula, with D. eilensis, D. galgallensis, D. sulcata and D. velutina. In sect. Duvalia there occur di-, tetra- and hexaploids, while in sect. Arabica only diploid taxa are found together with tetraploid cytotypes. Polyploidy is obviously of major significance for the speciation and distribution of the S African taxa. This is also corroborated by hybridisation experiments. Some of the diploid species are rare and have a narrow distribution, indicating their relict state. The small number of components of flavonoid aglycons found in sect. Duvalia is still more reduced in sect. Arabica. — The chromosome and biogeographical data suggest that the origin of Duvalia was in East Africa, perhaps in the Horn of Africa. The present distribution is obviously due to north- and southward migration. The sister genus of Duvalia is probably Huernia, while similarities with Piaranthus are obviously due to parallel evolution.
KeywordsCorolla Tube Flavonoid Aglycon Southward Migration Diploid Taxon Tetraploid Cytotypes
Unable to display preview. Download preview PDF.