Genomic signatures of environmental selection despite near-panmixia in summer flounder

Rapid environmental change is altering the selective pressures experienced by marine species. While adaptation to local environmental conditions depends on a balance between dispersal and natural selection across the seascape, the spatial scale of adaptation and the relative importance of mechanisms maintaining adaptation in the ocean are not well understood, Here, using population assignment tests, Approximate Bayesian Computation (ABC), and genome scans with double-digest restriction-site associated DNA sequencing data, we evaluated population structure and locus-environment associations in a commercially important species, summer flounder (Paralichthys dentatus), along the U.S. east coast. Based on 1137 single nucleotide polymorphisms across 232 individuals spanning nearly 1900 km, we found no indication of population structure across Cape Hatteras, North Carolina (FST = 0.0014) or of isolation by distance along the coast using individual relatedness. ABC estimated the probability of...