Data from: Genomic diversity, population structure, and migration following rapid range expansion in the balsam poplar, Populus balsamifera

Rapid range expansions can cause pervasive changes in the genetic
diversity and structure of populations. The post-glacial history of the
Balsam Poplar, Populus balsamifera, involved the colonization of most of
northern North America, an area largely covered by continental ice sheets
during the last glacial maximum. To characterize how this expansion shaped
genomic diversity within and among populations, we developed 412 SNP
markers that we assayed for a range-wide sample of 474 individuals sampled
from 34 populations. We complemented the SNP dataset with DNA sequence
data from 11 nuclear loci from 94 individuals, and used coalescent
analyses to estimate historical population size, demographic growth, and
patterns of migration. Bayesian clustering identified three geographically
separated demes found in the Northern, Central, and Eastern portions of
the species range. These demes varied significantly in nucleotide
diversity, the abundance of private polymorphisms, and population
substructure. Most measures supported the Central deme as descended from
the primary refuge of diversity. Both SNPs and sequence data suggested
recent population growth, and coalescent analyses of historical migration
suggested a massive expansion from the Center to the North and East.
Collectively, these data demonstrate the strong influence that range
expansions exert on genomic diversity, both within local populations and
across the range. Our results suggest that an in-depth knowledge of
nucleotide diversity following expansion requires sampling within multiple
populations, and highlight the utility of combining insights from
different data types in population genomic studies.