Evolutionary history of Pinguicula sect. Pinguicula (Lentibulariaceae)

Although the main evolutionary lineages within Pinguicula have been identified, relationships at lower taxonomic levels remain unclear. In this study, we focused on P. sect. Pinguicula, the most species-rich group of butterworts in Europe, to identify key evolutionary lineages and explore potential speciation pathways. To achieve this, we applied cytological (karyology and flow cytometry) and molecular (AFLP and DNA sequencing) approaches. Contrary to literature records stating three ploidy levels, we found that P. sect. Pinguicula probably comprises taxa of only two ploidy levels—tetraploid (2n = 32) and octoploid (2n = 64). Despite the continuous variation in genome size between taxa, which can help in their delimitation, this trait lacks phylogenetic signal. Sequenced regions confirmed low sequence divergence, but the pattern of polymorphisms and duplications, together with AFLP data, allowed us to infer possible diversification routes. Hybridization and polyploidization within hybrid swarms appear to have played a crucial role in diversification. Tetraploid taxa and hybridization between them, followed by polyploidization and geographical isolation, probably set the wheel of speciation in motion. Pleistocene climatic oscillations further influenced this process by repeatedly expanding and contracting suitable habitats, facilitating additional hybridization and speciation events. Notably, octoploid taxa exhibit high genetic uniformity, suggesting they originated from a restricted gene pool.