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 dispersal across the biogeographic break at Cape Hatteras to be high (95% credible interval: 7-50% migration). However, we found 15 loci whose allele frequencies were associated with at least one of four environmental variables. Of those, 11 were correlated with bottom temperature. For summer flounder, our results suggest continued fisheries management as a single population and identify likely response mechanisms to climate change. Broadly, our findings suggest that spatial balancing selection can manifest in adaptive divergence on regional scales in marine fish despite high dispersal, and that these conditions likely result in the widespread distribution of adaptive alleles and a high potential for future genetic adaptation in response to changing environmental conditions. In the context of a rapidly changing world, a landscape genomics perspective offers a useful approach for understanding the causes and consequences of genetic differentiation.
All summer flounder SNPs following bioinformatics filters
VCF file containing ddRADseq data for summer flounder. This file contains all SNPs remaining following bioinformatics filters.
SNP.DP3g95maf05.FIL.FIL.recode.updated.vcf
1137 summer flounder SNPs
VCF file containing ddRADseq data for summer flounder. This file contains the first SNP on each contig, resulting in 1137 SNPs. These SNPs were used in the main analyses.
SNP.DP3g95maf05.FIL.FIL.recode.updated.onesnp.vcf
Structure formatted file made from SNP.DP3g95maf05.FIL.FIL.recode.updated.onesnp.vcf
This file is formatted for input in the program STRUCTURE. It contains 1137 SNPs across 241 summer flounder. The first column identifies an individual fish. There are two rows for every fish. The second column is a population identifier. Columns 3-1139 are SNPs. Values of 1-4 indicate nucleotides (A = 1, T = 2, G = 3, C = 4). Missing data are indicated by -9.
structure_input_Nov_11_2015.str
Structure formatted file containing 1137 SNPs across 232 fish in main analyses
This file is formatted for input into the program STRUCTURE. It contains 1137 SNPs across 232 summer flounder. These were the individuals used in the main analyses, and this file was used to create the input files for BayEnv2. The first column identifies an individual fish. There are two rows for every fish. The second column is a population identifier. Columns 3-1139 are SNPs. Values of 1-4 indicate nucleotides (A = 1, T = 2, G = 3, C = 4). Missing data are indicated by -9.
structure_input_232forbayenv.str
Summer flounder metadata
This files contains metadata for the 232 summer flounder used in the main analyses. Data include the individual ID used for sequencing, capture date, sex, total length (cm), maturity status, collecting agency, latitude, longitude, calculated distance from a southern point, depth of capture, bottom temperature at capture, bottom salinity at capture and population grouping for BayEnv2 analysis.
pade_metadata.txt
est file for generating simulations in fastsimcoal
One of two files used to generate simulations in fastsimcoal for ABC analysis. The other necessary file is: migrationABC_DNA1millionby100.tpl.
migrationABC_5729_2_0.5dispersal.est
tpl file for generating simulations in fastsimcoal
One of two files used to generate simulations in fastsimcoal for ABC analysis. The other necessary file is: migrationABC_5729_2_0.5dispersal.est.
migrationABC_DNA1millionby100.tpl
Script that uses the .est and .tpl files to generate fastsimcoal simulations
This script can be used to submit many fastsimcoal jobs to a computing cluster. It uses the parameters in the migrationABC_DNA1millionby100.tpl and migrationABC_5729_2_0.5dispersal.est files to generate 500 coalescent simulations each time it is submitted.
run_fsc.sh