Format: ORAL

Filip Kolr, Sonia Celestini, Veronika Konecn, Magdalena Bohutnsk

Department of Botany, Faculty of Science, Charles University, Benátská 2, 128 01 Prague, Czech Republic

Repeated adaptation provides valuable insight into the predictability of evolutionary change through replicated natural experiments. We investigated the strength and genomic underpinnings of repeated local adaptation of two outcrossing Arabidopsis species (A. arenosa, A. lyrata) towards challenging environments. Based on structured sampling and genome sequencing of 50 ecologically divergent populations, transplant experiments and population genomics, we discovered rapid multi-parallel adaptation towards different environmental gradients (high elevations, toxic soils) and detected significant over-representation of shared adaptive candidate genes for each environment. Although vast majority of the parallel candidates sourced on shared allelic variation, we also discovered a small fraction of genes exhibiting convergent evolution from independent de novo mutations. In addition, a significant number of genes was identified repeatedly as candidates to two or more different environments (e.g. challenging soils and alpine), suggesting spatio-environmentally fluctuating selection may further contribute to the maintenance of diverse pools of adaptive standing variation. Then, we complemented our investigations with additional published gene lists and our genome scans from other Brassicaceae genera and found that the extent of genomic parallelism significantly decreased with increasing divergence between the compared lineages. This relationship was explained by decreasing probability of repeated selection on the same standing or introgressed alleles. We therefore conclude that genetic divergence between populations, species and genera, affecting the pool of shared variants, is an important factor in the predictability of genome evolution.