title: Evolutionary trends in the distylous genus Pulmonaria (Boraginaceae): Evidence of ancient hybridization and current interspecific gene flow.
abstract: The distylous genus Pulmonaria contains approximately 18 species that are widely distributed across Eurasia. Previous studies have shown that species delimitation in the genus is problematic, but have not yet explored the evolutionary history of the genus. Premating reproductive barriers between European species appear to be weak, as several species have strongly overlapping distribution areas, flower at the same time and share the same pollinators, suggesting that hybridization may have contributed to the evolutionary history of Pulmonaria. To test this hypothesis, phylogenetic analyses of nuclear ITS and plastid data (rps16, trnH-psbA, rpl16) from 48 allopatric and four sympatric populations were performed to (1) provide a molecular phylogeny for nine of the most common Pulmonaria species in Europe, (2) detect current and ancient hybridization events, and (3) assess the contribution of hybridization versus incomplete lineage sorting to the inferred phylogenetic patterns. Our results showed that gene trees displayed widespread, strongly supported incongruence associated with the conflicting position of hybrid samples rather than incomplete lineage sorting. Evidence was found of different degrees of hybridization, ranging from current interspecific gene flow at secondary contact zones to introgression at the population level and at least one event of hybrid speciation. Overall, these results suggest that hybridization and introgression were - and could still be - important processes affecting speciation in the genus Pulmonaria.
authors.affiliation: KU Leuven, Department of Biology, Plant Population and Conservation Biology, Kasteelpark Arenberg 31, 3001 Heverlee, Belgium; Biological and Environmental Sciences, University of Stirling, Stirling FK9 4LA, UK. Electronic address: sofie.meeus@stir.ac.uk.
authors.forename: Sofie
authors.initials: S
authors.lastname: Meeus
authors.affiliation: KU Leuven, Department of Biology, Plant Population and Conservation Biology, Kasteelpark Arenberg 31, 3001 Heverlee, Belgium; Botanic Garden Meise, Nieuwelaan 38, BE-1860 Meise, Belgium.
authors.forename: Steven
authors.initials: S
authors.lastname: Janssens
authors.affiliation: KU Leuven, Department of Biology, Plant Population and Conservation Biology, Kasteelpark Arenberg 31, 3001 Heverlee, Belgium.
authors.forename: Kenny
authors.initials: K
authors.lastname: Helsen
authors.affiliation: KU Leuven, Department of Biology, Plant Population and Conservation Biology, Kasteelpark Arenberg 31, 3001 Heverlee, Belgium.
authors.forename: Hans
authors.initials: H
authors.lastname: Jacquemyn
mesh_terms: D005060:Europe; D019143:Evolution, Molecular; D051456:Gene Flow / Q000235:genetics*; D006824:Hybridization, Genetic; D010802:Phylogeny; D018087:Plastids / Q000235:genetics; D029685:Pulmonaria / Q000145:classification* / Q000235:genetics*; D013045:Species Specificity; D061350:Sympatry
keywords: Distyly; Hybridization; Interspecific gene flow; Introgression; Lineage sorting; Mating barriers