Data from: Genetic heterogeneity underlying variation in a locally adaptive clinal trait in Pinus sylvestris revealed by a Bayesian multipopulation analysis

Local adaptation is a common feature of plant and animal populations.
Adaptive phenotypic traits are genetically differentiated along
environmental gradients, but the genetic basis of such adaptation is still
poorly known. Genetic association studies of local adaptation combine data
over populations. Correcting for population structure in these studies can
be problematic since both selection and neutral demographic events can
create similar allele frequency differences between populations.
Correcting for demography with traditional methods may lead to eliminating
some true associations. We developed a new Bayesian approach for
identifying the loci underlying an adaptive trait in a multipopulation
situation in the presence of possible double confounding due to population
stratification and adaptation. With this method we studied the genetic
basis of timing of bud set, a surrogate trait for timing of yearly growth
cessation that confers local adaptation to the populations of Scots pine
(Pinus sylvestris). Population means of timing of bud set were highly
correlated with latitude. Most effects at individual loci were small.
Interestingly, we found genetic heterogeneity (that is, different sets of
loci associated with the trait) between the northern and central European
parts of the cline. We also found indications of stronger stabilizing
selection toward the northern part of the range. The harsh northern
conditions may impose greater selective pressure on timing of growth
cessation, and the relative importance of different environmental cues
used for tracking the seasons might differ depending on latitude of
origin.