New insights on adaptation and population structure of cork oak using genotyping by sequencing

Abstract

Species respond to global climatic changes in a local context. Understanding this process is paramount due to the pace of these changes. Tree species are particularly interesting to study in this regard due to their long generation times, sedentarism, and ecological and economic importance. Quercus suber L. is an evergreen forest tree species of the Fagaceae family with an essentially Western Mediterranean distribution. Despite frequent assessments of the species evolutionary history, large-scale genetic studies have mostly relied on plastidial markers, whereas nuclear markers have been used on studies with locally focused sampling strategies. The potential response of Q. suber to global climatic changes has also been studied, under ecological modelling. In this work, \"Genotyping by Sequencing\" (GBS) is used to derive 2,547 SNP markers to assess the species evolutionary history from a nuclear DNA perspective, gain insights on how local adaptation may be shaping the species genetic background, and to forecast how Q. suber may respond to global climatic changes from a genetic perspective. Results reveal an essentially unstructured species, where a balance between gene flow and local adaptation keeps the species gene pool somewhat homogeneous across its distribution, but at the same time allows variation clines for the individuals to cope with local conditions. \"Risk of Non-Adaptedness\" (RONA) analyses, suggest that for the considered variables and most sampled locations, the cork oak does not require large shifts in allele frequencies to survive the predicted climatic changes. However, more research is required to integrate these results with those of ecological modelling.