An association of genetic structure with bioclimatic variables and longitude and latitude was tested using GESTE. The highest probability model of our GESTE analysis suggests an association of only Bio10 (Mean Temperature of Warmest Quarter) with genetic structure over Europe (posterior probability = 0.228, marginal probability = 0.568, α = −0.63). For the analyzed populations, the genetic differentiation decreases with increasing summer temperatures (Fig. S1). In contrast, neither geographic distance nor winter cold explain the observed genetic differentiation.