This repository contains data and code for Fisher et al. (in review) Ecology & Evolution.
- Metadata on samples, final genepop files, key output from Stacks, and other formatted data files required to re-run analyses can be found in the data folder
- R and Python scripts to re-run analyses and produce the figures in the manuscript are in the scripts folder
- Results from analyses that are reported in the manuscript, and
.pngfiles of figures in the manuscript / supplementary material, are int he results folder - Some additional documentation is provided in the doc folder
Small and isolated peripheral populations, which are often remnants of glacial refugia, offer an opportunity to determine the magnitude and direction of fine-scale connectivity in high gene flow marine species. When located at the equatorial edge of a species’ range, these populations may also harbor genetic diversity related to survival and reproduction at higher temperatures, a critical resource for marine species facing warming ocean temperatures. Pacific cod (Gadus macrocephalus), a marine fish in the North Pacific, has already experienced major shifts in biomass and distribution linked to climate change. We estimated the magnitude and direction of connectivity between peripheral populations of Pacific cod at the southern edge of the species’ range, by conducting restriction site-associated DNA (RAD) sequencing and individual assignment on fish collected around the Korean Peninsula during the spawning season. Three populations on the western, eastern, and southern Korean coasts were highly differentiated (FST =0.025 – 0.042) and relatively small (Ne = 433-1777). Ten putative dispersers revealed unidirectional, west-to-east movement around the Korean Peninsula, at a higher rate than predicted by indirect estimates of connectivity (FST). Allele frequencies at 87 RAD loci were decisively correlated with strong marine temperature gradients between the warmer southern coast and cooler waters of the eastern and western coasts. This is the first direct evidence of gene flow from genetically isolated peripheral populations potentially supplying adaptive alleles to larger northern populations. Our study emphasizes the conservation value of peripheral populations in high gene flow marine fish species.