Differentiation of the endemic Greek genus Hymenonema and its relatives of subtribe Scolyminae (Compositae, Cichorieae) based on a multilocus species tree reconstruction

Abstract

Hymenonema (Compositae, tribe Cichorieae) together with the genera Catananche, Gundelia, and Scolymus forms the subtribe Scolyminae. It is endemic to Greece and consists of two species, Hymenonema laconicum and Hymenonema graecum, which occur in the south Peloponnisos and central Aegean area, respectively. The present contribution aims at a phylogenetic reconstruction of evolutionary relationships among the 12 species of the subtribe, focusing on the temporal and spatial framework for its evolution. The phylogenetic relationships among the members of Scolyminae were inferred from molecular data based on the multi-copy region of the nrDNA internal transcribed spacers ITS1 and ITS2, two intergenic spacers of the cpDNA (trnL-trnF, rpl32-trnL), and one single-copy nuclear region (D10). The gene trees were reconstructed using Bayesian phylogenetic methods. All gene trees support the monophyly of Hymenonema and the sister-group relationship with the genus Scolymus. The further sister-group relationship of this group (Hymenonema–Scolymus) with Catananche is also supported by nrDNA and cpDNA analyses. Finally, a species tree (inferred in a Bayesian coalescent framework) was reconstructed and dates the divergence time between the two Hymenonema species to the Pleistocene (around 1.3 Ma ago). Maximum likelihood-based biogeographical reconstructions suggest a Miocene (pre-Messinian) differentiation of the subtribe on the northern Tethyan platform, followed by Miocene/Pliocene dispersal events to the western Mediterranean and North-African platforms and final, small-scale vicariance events within the genera in the Pleistocene.