Evidence of divergent selection for drought and cold tolerance at landscape and local scales in Abies alba Mill. in the French Mediterranean Alps

Understanding local adaptation in forest trees is currently a key research and societal priority. Geographically and ecologically marginal populations provide ideal case studies, because environmental stress along with reduced gene flow can facilitate the establishment of locally adapted populations. We sampled European silver fir (Abies alba Mill.) trees in the French Mediterranean Alps, along the margin of its distribution range, from pairs of high and low elevation plots on four different mountains situated along a 170 km east-west transect. The analysis of 267 SNP loci from 175 candidate genes suggested a neutral pattern of east-west isolation-by-distance among mountain sites. FST outlier tests revealed 16 SNPs that showed patterns of divergent selection. Plot climate was characterized using both in-situ measurements and gridded data that revealed marked differences between and within mountains with different trends depending on the season. Association between allelic frequencies an...