Untangling the origin and diversification of the Carthamus–Carduncellus complex (Cardueae, Compositae) in the Mediterranean basin

Understanding the richness and diversification processes in the Mediterranean basin requires both knowledge of the current environmental complexity and paleogeographic and paleoclimate events and information from studies that introduce the temporal dimension. The Carthamus–Carduncellus complex (Cardueae, Compositae) constitutes a good case study to investigate the biogeographic history of this region because it evolved throughout the basin. We performed molecular dating, ancestral area estimation, and diversification analyses based on previous phylogenetic studies of a nearly complete taxon sampling of the complex. The main aims were to determine the role of tectonic and climatic events in the disjunction of the complex and the expansion route of the two main lineages, Carduncellus s.l. and Carthamus. Our results suggest that the main lineages in the complex originated during the Miocene. Later, all main paleogeographic and paleoclimatic events during the Neogene and Pleistocene in the Mediterranean basin had an important imprint on the evolutionary history of the complex. The Messinian Salinity Crisis facilitated the dispersion of the genus Carduncellus from North Africa to the Iberian Peninsula and the split of the genera Phonus and Femeniasia from the Carduncellus lineage. The onset of the Mediterranean climate in the Pliocene together with some orogenic processes could be the main causes of the diversification of the genus Carduncellus. In contrast, Pleistocene glaciations played a key role in the species diversification of Carthamus. In addition, we emphasize the problems derived from secondary dating and the existing differences between two previous dating analyses of the tribe Cardueae.