Population genomics reveals high gene flow in grass rockfish (Sebastes rastrelliger).

Variation at the genomic level is important for understanding a species' demographic and phylogenetic history, in addition to identifying candidate regions that may be under selection and important to local adaptation. We used restriction-site associated DNA (RAD) sequencing to sample single nucleotide polymorphisms (SNPs) from the grass rockfish genome (Sebastes rastrelliger) to assess range-wide patterns of population structure and test for signatures of selection (i.e. outlier loci). Two different filtering criteria yielded 6572 and 10,393 SNPs that were genotyped in over 70% of 110 individuals from six sampling areas using RAD loci. Global FST across sampling sites is 0.0009-0.002 for all loci. Two methods for the detection of outlier loci failed to identify any outlier loci. Clustering analyses and discriminant analysis of principal components were not able to detect any population structure in our dataset. These results suggest high levels of gene flow for this species across its range and that this level of gene flow makes it difficult to detect outlier loci in the current dataset.