The potentially significant genetic consequences associated with the loss of migratory capacity of diadromous fishes which have become landlocked in freshwater are poorly understood. Consistent selective pressures associated with freshwater residency may drive repeated differentiation both between allopatric landlocked and anadromous populations and within landlocked populations (resulting in sympatric morphs). Alternatively, the strong genetic drift anticipated in isolated landlocked populations could hinder consistent adaptation, limiting genetic parallelism. Understanding the degree of genetic parallelism underlying differentiation has implications for both the predictability of evolution and management practices. We employed an 87k SNP array to examine the genetic characteristics of landlocked and anadromous Arctic Charr (Salvelinus alpinus) populations from five drainages within Labrador, Canada. One gene was detected as an outlier between sympatric, size-differentiated morphs in each of two landlocked lakes. While no single locus differentiated all replicate pairs of landlocked and anadromous populations, several SNPs, genes, and paralogs, were consistently detected as outliers in at least 70% of these pairwise comparisons. A significant C-score suggested the amount of shared outlier SNPs across all paired landlocked and anadromous populations was greater than expected by chance. Our results indicate that despite their isolation, selection due to the loss of diadromy may drive consistent genetic responses in landlocked populations.

This dryad repository contains 12 text (.txt) files in genepop format (corresponding to each of 12 locations where Arctic Charr (Salvelinus alpinus) samples were collected) and 1 metadata (.csv) file. Please see article and README file for additional details.