Taxonomy, phylogeny and biogeography of Kickxia and Nanorrhinum (Scrophulariaceae)

Phylogenetic studies in Kickxia sensu lato, using morphological characters, show that two groups of species appear as distinct clades, one corresponding to sect. Kickxia and the other corresponding to sect. Valvatae. The differences between the two sections are of the same magnitude as those used to separate other closely related genera in the tribe. Therefore, the treatment of sect. Valvatae as a separate genus, Nanorrhinum , is proposed. Results from a dispersal-vicariance analysis indicate that the area of origin for Nanorrhinum is Arabia, whereas for Kickxia sensu stricto it is either Macaronesia, the Mediterranean Region or both these areas combined. The taxonomy of Nanorrhinum is revised in detail, whereas for Kickxia a synoptical treatment is given, mainly based on previous literature. The results indicate that the plasticity of the species of Nanorrhinum , as well as the variation within populations in the field, is often much greater than previously thought, and that, therefore, far too many species have been described. In the present study ten species are recognized in Nanorrhinum. New combinations are N. azraqensis, N. stenanthum, N. hastatum, N. elegans, N. kuriensis, N. asparagoides, N. heterophyllum and N. woodii. Three lectotypes are selected. Keys to all taxa are given, and new information on chromosome numbers and sexual systems are provided for several species.