Data from: Phylogenomic analyses reveal latitudinal population structure and polymorphisms in heat stress genes in the North Atlantic snail Nucella lapillus

North Atlantic rocky intertidal species have been shaped by repeated
glaciations and strong latitudinal temperature gradients, making them an
excellent system to study postglacial phylogeography and thermal
tolerance. Population genetics data from northwestern Atlantic species,
however, often show patterns inconsistent with the prediction that high
dispersal should generate weaker genetic structure among populations. Here
we used next-generation sequencing restriction-associated DNA tags
(RAD-seq) and a transcriptome assembled from RNA-seq data to analyze the
genetic structure of northwestern Atlantic populations of the
low-dispersal intertidal snail Nucella lapillus. Although previous studies
in this region have detected almost no genetic structure in N. lapillus,
our phylogenomic approach identified a well-supported split between
northern and southern clades. By comparing RAD-seq data and our
transcriptome assembly, we identified thousands of fixed single-nucleotide
polymorphisms (SNPs) between these latitudinal clades that map to
protein-coding genes, including genes associated with heat-stress
tolerance. These fixed SNPs might represent loci under selection for
different thermal regimes in the northwestern Atlantic.