Phylogeny and evolutionary diversification of Adenocarpus DC. (Leguminosae)

Phylogenetic relationships of Adenocarpus species were assessed by sequence analyses of the ITS and 3′ end of ETS (nrDNA) regions and the trnL–trnF intergenic spacer (cpDNA). The nrDNA analysis recovered four main clades within Adenocarpus . Clades 1–3 comprise morphological and molecularly well–differentiated species that occur in the western Mediterranean realm. Clade 4 comprises three distinctive endemic species from the Canary Islands, an endangered Algerian endemic, and a set of species close to A. complicatus with distinct geographical areas but with little molecular variation between taxa. The latter species are centred in the Iberian Peninsula but also distributed along the Mediterranean basin (from the Iberian Peninsula to Turkey). The phylogenetic position of A. mannii , a morphologically distinctive species with a unique afro–tropical distribution, is not unequivocally resolved, being sister to clade 3 in the ETS tree but to clade 4 in the ITS tree. Rates of evolution and ages of divergence of major groups were estimated using nonparametric rate smoothing with a fixed calibration point of 41.2 Ma and constraining the node of the separation of Anarthrophyllum and Mediterranean Genisteae at a minimum age of 13.6 and a maximum of 25.8 Ma. The estimated ages indicate that the diversification of Adenocarpus and first separation of two lineages may have occurred during the onset and the wake of the profound Middle Miocene cooling episode. One of the lineages separated rapidly into two groups (clades 1 and 2) while the second one led to clade 3, A. mannii and clade 4. Clades 1, 2 and 3 differentiated into the present species soon after these major events whereas clade 4 radiated much later, during the Pliocene.