Format: ORAL

Judita Zozomov-Lihov1, Adam Kantor1, Marek lenker1, Stanislav paniel1

1 Plant Science and Biodiversity Centre, Slovak Academy of Sciences, Bratislava, Slovak Republic

Recently diversified and polyploid-rich plant lineages pose a challenge for both taxonomic and evolutionary studies. Recent speciation, recurrent polyploid formation, involving both auto- and allopolyploidy, and permeable reproductive barriers between species with historical and recent gene flow result in intricate species complexes. These are characterized by high diversity, but phylogenetic inferences often yield shallow, largely unresolved or conflicting phylogenetic structuring. Genome-scale data obtained by high-throughput DNA sequencing, as well as recent developments in phylogenetic approaches that account for reticulate and polyploidization events, provide excellent opportunities to improve phylogenetic inferences and gain insights into such evolutionarily challenging lineages. We illustrate these advances in our studies of polyploid species complexes in Brassicaceae genera by applying ddRADseq and target enrichment with genome skimming (Hyb-Seq). The studied species complexes show the highest diversity and concentration of polyploid endemics in southern Europe, which probably evolved through repeated cycles of glaciation-induced range shifts, isolation of populations in multiple refugia, followed by range expansions and secondary contacts. In Alyssum, we found evidence of introgression events between diploids both within and between clades and revealed a unique case of parallel polyploid speciation with eight sibling polyploids containing subgenomes from the same two diploid progenitors. In Cardamine and Odontarrhena, when specifically targeting the Eastern Mediterranean region, we detected both historical and recent interspecific gene flow and elucidated the origin of several auto- and allopolyploids. We identified diversity hotspots that may result from long-term species persistence and diversity accumulation in situ, but also arise as melting pots favoring species contacts and polyploid evolution. Overall, our studies highlight the evolutionary role of hybridization and polyploidy in stimulating plant speciation in southern Europe and demonstrate the power of thorough phylogenomic approaches when studying reticulate evolution in polyploid species complexes.