Can northern sessile oaks profit from southern genetic variants to face future climate change?

In addition to valuable renewable wood resources, oak forests are essential ecosystems hosting a large amount of biodiversity. Although oaks are predicted to be less affected by a shift in climatic conditions, including more frequent and severe drought spells, compared to other forest tree species, they will have to adapt fast to future climatic changes. Here we use classical landscape genomics to locate genes with a potential adaptive role in drought-resistance among pan-European provenances of sessile oak (Quercus petraea). We ask if an enrichment with alleles beneficial for dry conditions from southern provenances often subjected to drought – be it by natural dispersal, gene flow or human plantings – can enhance the adaptive potential of the native Danish Q. petraea populations to a future drier climate. We find numerous genetic loci (single nucleotide polymorphisms; SNPs) associated with bioclimatic variables describing local precipitation. While many of the associated SNPs are found in inter-genic regions, some are indeed located in, or close to genes, known to be involved in drought stress responses. Thus, beneficial alleles have the potential to spread across the landscape. We will present detailed analyses of these beneficial alleles in order to determine whether they are absent in the local Danish gene pool, or if they are already present at low frequency, and thus enabling adaptation to a drier climate based on standing genetic variation. In conclusion, beneficial alleles found among southern populations of sessile oak is a valuable source for future enrichment of northern oak seed sources and natural populations to ensure their robustness under future climate.