Format: ORAL

Ting-Shen Han1,2, Yao-Wu Xing1

1 CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Yunnan, China 2 Department of Chromosome Biology, Max Planck Institute for Plant Breeding Research, Cologne, Germany

Yellowcress (Rorippa Scop.) is a Brassicaceae genus with an accepted 86 species and a worldwide distribution characterized by amphitropical disjunction. Most of Rorippa species have affinity for wet habitats, where migrating birds may transit their seeds or propagules far from local populations. They also have robust tolerance to whole-genomic changes, such as interspecific hybridization and polyploidization. About 70% of Rorippa are polyploids, and 90% of them are endemic to specific continents. Rorippa polyploids are globally distributed but more prevalent in the Southern Hemisphere (accounting for 91% of species). These observations highlight a potential role of long-distance dipsersal (LDD) in shaping the amphitropical disjunction of Rorippa and suggest that polyploidy may have promoted effective LDD. To test the polyploid role in LDD, we traced the biogeographic and speciation history for 17 diploids and 41 polyploids of Rorippa using variation from plastid genomes and multiple nuclear loci. The ploidy role in dispersal rate difference was demonstrated using trait-dependent biogeographic modeling. We demonstrate that polyploidy would be not only a driver but also a responder of LDD in Rorippa, highlighting a synergistic relationship between them. Our results provide a framework to uncover the biogeographic consequences of polyploidization and the joint roles of polyploidy and LDD in shaping the distribution of biodiversity.