Populations residing near species' low-latitude range margins (LLM) often occur in warmer and drier environments than those in the core range. Thus, their genetic composition could be shaped by climatic drivers that differ from those occurring at higher latitudes, resulting in potentially adaptive variants of conservation value. Such variants could facilitate the adaptation of populations from other portions of the geographic range to similar future conditions anticipated under ongoing climate change. However, very few studies have assessed standing genetic variation at potentially adaptive loci in natural LLM populations. We investigated standing genetic variation at SNPs located within 117 candidate genes and its links to putative climatic selection pressures across 19 pedunculate oak (Quercus robur L.) populations distributed along a regional climatic gradient near the species' southern range margin in southeastern Europe. These populations are restricted to floodplain forests along large lowland rivers, whose hydric regime is undergoing significant shifts under modern rapid climate change. The populations showed very weak geographic structure, suggesting extensive genetic connectivity and gene flow or shared ancestry. We identified eight (6.2%) positive FST-outlier loci, and genotype-environment association analyses revealed consistent associations between SNP allele frequencies and several climatic variables linked to water availability. A total of 61 associations involving 37 SNPs (28.5%) from 35 annotated genes provided important insights into putative functional mechanisms in our system. Our findings provide empirical support for the role of LLM populations as sources of potentially adaptive variation that could enhance species’ resilience to climate change-related pressures.

SNP_genotypes_Dryad

The data are SNP genotypes of the 380 Quercus robur individuals from 19 populations used in this study. See readme sheets in SNP_genotypes_Dryad.xls

Variable_values_Dryad

The data are extracted values of climatic variables for each of the 19 Quercus robur populations, used in GEA analyses. See readme sheet in Variable_values_Dryad.xls