Phylogeny of highly hybridogenous Iberian Centaurea L. (Asteraceae) taxa and its taxonomic implications

Centaurea is one of the richest but less investigated genera of tribe Cardueae (Asteraceae). We reconstructed an updated phylogeny of Iberian species of Centaurea sects. Centaurea, Jacea, Lepteranthus and Phalolepis by sampling representatives from 48 taxa (~60% of the taxonomic variation). Phylogenetic trees and haplotypic networks were based on ITS and trnLF sequences, and Bayesian dating analysis on ITS data. We found two main lineages within this monophyletic group: (1) a W Mediterranean Centaurea and Phalolepis plus C. diffusa (CP) clade; and (2) an E Mediterranean – Eurosiberian Jacea and Lepteranthus (JL) clade. Our analyses provide new reconstructions for species of C. sects. Jacea and Lepteranthus that support new taxonomic circumscriptions. The inferred divergence times indicated succesive splits of the CP and JL lineages during the Miocene (e.g. CP/JL, Serravalian; Jacea/Lepteranthus, Tortonian; C. hyssopifolia, C. gr. janeri, C. gr. exarata, Messinian) and the Pliocene (C. linifolia/C. antennata). Interspecific hybridizations and polyploidizations likely took place during the Pleistocene (1.5–0.7 Ma) interglacials, when several hybrid lineages apparently originated (e.g. C. x decipiens). Allopatric speciation probably played an important role in the diversification of the Iberian Centaurea taxa, since the origins of several endemic species occurred during mid-late Pleistocene times (2.2–1.3 Ma) in several disjunct Iberian ranges.