Format: ORAL

Nlida Padilla-Garca1, Jakub Vlcek1, Simon Martin2, Vivaswat Shastry3, Joern Gerchen1, Filip Kolr1

1 Charles University, Prague, Czech Republic 2 Institute of Ecology and Evolution, The University of Edinburgh, United Kingdom 3 University of Chicago, Chicago, USA

Polyploidy, the presence of multiple genome copies as a result of whole-genome duplications (WGD), is an important speciation mechanism in plants. WGD has been traditionally assumed to cause immediate reproductive isolation due to strong genetic incompatibilities leading to sterility between polyploids and their diploid progenitors and/or inviability of inter-ploidy offspring. However, recent field surveys, cytological and population genetic studies have demonstrated that gene flow between plants with different ploidy levels can happen in natural populations. Yet, it remains unclear how common such inter-ploidy introgression is and to what degree it contributes to plant adaptation. Here we present new results on Arabidopsis arenosa, a natural plant system in which both diploids and autotetraploids are present. We focused on one primary and three secondary contact zones across Europe, where diploid and tetraploid individuals of A. arenosa are found coexisting in mixed-ploidy populations and/or in geographically closed diploid and tetraploid populations. We used whole-genome sequencing to test for inter-ploidy gene flow on both genome-wide as well as local genomic scales. We found significant evidence of introgressed genomic regions across contact zones. We also identified genomic regions that can be acting as barriers to introgression between different ploidy levels. We identified the genes localized in these regions and we performed GO enrichment in order to interpret how their functions could have contributed to adaptation of polyploids. Overall, our study provides further genomic evidence of inter-ploidy introgression across the genome and across different contact zones in a natural plant system and how this introgression may have an impact in the adaptation of polyploid lineages.