Data from: Inferring selection in instances of long‐range colonization: the Aleppo pine (Pinus halepensis) in the Mediterranean Basin

Teasing apart the effects of natural selection and demography on current
allele frequencies is challenging, due to both processes leaving a similar
molecular footprint. In particular, when attempting to identify selection
in species that have undergone a recent range expansion, the increase of
genetic drift at the edges of range expansions (“allele surfing”) can be a
confounded factor. To address this potential issue, we first assess the
long-range colonisation history of the Aleppo pine across the
Mediterranean Basin, using molecular markers. We then look for single
nucleotide polymorphisms (SNPs) involved in local adaptation using: (i)
environmental correlation methods (Bayenv2), focusing on bioclimatic
variables important for the species’ adaptation (i.e. temperature,
precipitation and water availability); and (ii) FST-related methods
(PCAdapt). In order to assess the rate of false positives caused by the
allele surfing effect, these results are compared with results from
simulated SNP data that mimics the species’ past range expansions and the
effect of genetic drift, but with no selection. We find that the Aleppo
pine shows a previously unsuspected complex genetic structure across its
range, as well as evidence of selection acting on SNPs involved with the
response to bioclimatic variables such as drought. This study uses an
original approach to disentangle the confounding effects of drift and
selection in range margin populations. It also contributes to the
increased evidence that plant populations are able to adapt to new
environments despite the expected accumulation of deleterious mutations
that takes place during long-range colonisations.