Using molecular phylogenies to test phytogeographical links between East/South Africa-Southern Arabia and the Macaronesian islands -: a review, and the case of Vierea and Pulicaria section Vieraeopsis (Asteraceae)

We undertook a phylogenetic analysis of sequences of the internal transcribed spacers (ITS) of the nuclear ribosomal DNA to test the hypothesis that the Canary Island genus Vierea is closely related to Pulicaria sect. Vieraeopsis, a taxon with four species restricted to Socotra and Southern Arabia. The ITS tree does not support this relationship, although many of the nodes were weakly supported (bootstrap value below 75%). Vierea is sister to the Mediterranean genus Perralderia (bootstrap support 74%). We suggest that morphological similarities between Vierea and Pulicaria sect. Vieraeopsis are due mostly to morphological convergence. It is thus concluded that these two taxa do not share a common history. A review of molecular phylogenetic studies of taxa considered to represent putative biogeographical links between Macaronesia and Southern Arabia and/or distant regions of Africa, is also presented. With a few exceptions most of these putative relationships are not supported by molecular phylogenies. Additional cladistic studies are needed for at least 15 genera or sections with a predominant disjunet phytogeographical distribution between Macaronesia, East/South Africa and Southern Arabia.