Phylogenetic and taxonomic studies in the tribe Antirrhineae (Scrophulariaceae) with special reference to the genera Kickxia and Nanorrhinum

Abstract: The main aims of the present study are (1) to investigate phylogenetic relationships within the Antirrhineae using both morphological and molecular data, and (2) to provide an improved classification of the genus Kickxia sensu lato.Phylogenetic relationships within the tribe Antirrhineae are analysed and discussed on the basis of parsimony analyses of morphological and ndhF gene sequence data. The two sections currently generally recognized in Kickxia, sect. Kickxia and sect. Valvatae, were treated as terminal taxa in the analyses. The results indicate that the tribe Antirrhineae consists of four major groups of genera, the Anarrhinum clade, the Gambelia clade, the Maurandya clade, and the Antirrhinum clade. The Anarrhinum clade, consisting of Anarrhinum and Kickxia, is sister to the rest of the tribe. It is concluded that hummingbird-pollination has evolved independently within Antirrhineae at least three times from bee-pollinated ancestors.In a phylogenetic analysis of Kickxia sensu lato, using morphological characters, the two sections appear as distinct clades, both supported by strong synapomorphies. 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.A synoptical overview of Kickxia sensu stricto is given, whereas for Nanorrhinum a detailed taxonomic revision has been made. The results from studies of herbarium material, field work, and cultivation experiments, indicate that the plasticity of the species of Nanorrhinum is often greater than previously thought, and that, therefore, too many species have been described. In the present study ten species are recognized and many names are reduced to synonymy. New combinations are Nanorrhinum azraqensis, N. stenanthum, N. hastatum, N. elegans, N. kuriensis, N. asparagoides, N. heterophyllum and N. woodii. Distribution maps are provided for all species of Nanorrhinum, and somatic chromosome numbers are reported for several taxa. The revised taxonomy is used in an account of Kickxia and Nanorrhinum for the Flora of Ethiopia and Eritrea.