Data from: Do genetic drift and accumulation of deleterious mutations preclude adaptation? Empirical investigation using RADseq in a northern lacustrine fish

Understanding genomic signatures of divergent selection underlying
long-term adaptation in populations located in heterogeneous environments
is a key goal in evolutionary biology. In this study, we investigated
neutral, adaptive and deleterious genetic variation using 7,192 SNPs in 31
Lake Trout (Salvelinus namaycush) populations (n = 673) from Québec,
Canada. Average genetic diversity was low, weakly shared among lakes, and
positively correlated to lake size, indicating a major role for genetic
drift subsequent to lake isolation. Putatively deleterious mutations were
on average at lower frequencies than the other SNPs, and their abundance
relative to the entire polymorphism in each population was positively
correlated to inbreeding, suggesting that the effectiveness of purifying
selection was negatively correlated to inbreeding, as predicted from
theory. Despite evidence for pronounced genetic drift and inbreeding,
several outlier loci were associated with temperature and found in or
close to genes with biologically relevant functions notably related to
heat-stress and immune responses. Outcomes of gene-temperature
associations were influenced by the inclusion of the most inbred
populations, in which allele frequencies deviated the most from model
predictions. This result illustrates challenge in identifying
gene-environment associations in cases of high genetic drift and
restricted gene flow and suggests limited adaptation in populations
experiencing higher inbreeding. We discuss the relevance of these findings
for the conservation and management, notably regarding stocking and
genetic rescue, of Lake Trout populations and other species inhabiting
highly fragmented habitats.