Data from: Genetic divergence and signatures of natural selection in marginal populations of a keystone, long-lived conifer, eastern white pine (Pinus strobus) from northern Ontario

Marginal populations are expected to provide the frontiers for adaptation,
evolution and range shifts of plant species under the anticipated climate
change conditions. Marginal populations are predicted to show genetic
divergence from central populations due to their isolation, and divergent
natural selection and genetic drift operating therein. Marginal
populations are also expected to have lower genetic diversity and
effective population size (Ne) and higher genetic differentiation than
central populations. We tested these hypotheses using eastern white pine
(Pinus strobus) as a model for keystone, long-lived widely-distributed
plants. All 614 eastern white pine trees, in a complete census of two
populations each of marginal old-growth, central old-growth, and central
second-growth, were genotyped at 11 microsatellite loci. The central
populations had significantly higher allelic and genotypic diversity,
latent genetic potential (LGP) and Ne than the marginal populations.
However, heterozygosity and fixation index were similar between them. The
marginal populations were genetically diverged from the central
populations. Model testing suggested predominant north to south gene flow
in the study area with curtailed gene flow to northern marginal
populations. Signatures of natural selection were detected at three loci
in the marginal populations; two showing divergent selection with
directional change in allele frequencies, and one balancing selection.
Contrary to the general belief, no significant differences were observed
in genetic diversity, differentiation, LGP, and Ne between old-growth and
second-growth populations. Our study provides information on the dynamics
of migration, genetic drift and selection in central versus marginal
populations of a keystone long-lived plant species and has broad
evolutionary, conservation and adaptation significance.