A nuclear DNA basis for shelf‐ and bank‐scale population structure in northwest Atlantic cod (Gadus morhua): Labrador to Georges Bank

Abstract

Variation at five microsatellite DNA loci scored in ≈ 1300 individuals provided evidence of genetic structure among 14 cod (Gadus morhua) populations spanning the range of the species in the northwest (NW) Atlantic. Using DA and DSW measures of genetic distance, as well as FST and RST measures of population structure, differences are revealed among populations at continental shelf scales (NE Newfoundland Shelf, Grand Banks, Flemish Cap, Scotian Shelf, Georges Bank) where regions are separated by submarine saddles, channels and trenches. However, we also provide evidence of genetic structure at spawning‐bank scales consistent with variation in oceanographic features and in the spatiotemporal distribution of spawning, each of which may represent barriers to gene flow among geographically contiguous populations inhabiting a highly advective environment. The differences described are consistent with postdispersal spawning fidelity to natal areas, a behaviour that may be facilitated by topographically induced gyre‐like circulations that can act as retention mechanisms. Significant degrees of substructure among neighbouring and contiguous cod populations may be most easily explained by the associated oceanographic features and processes that conceivably form the template for the evolution of the structure. We suggest that bathymetric and hydrodynamic structure represents a rational starting point for developing hypotheses to examine the processes that lead to the genetic structuring of marine fish species.

Extent of mitochondrial DNA sequence variation in Atlantic cod from the Faroe Islands: a resolution of gene genealogy

“…These results are similar to our results for cytb variation within other countries (Á rnason and Pálsson, 1996; that show no evidence for historical population structure within a country. They contrast with results obtained from microsatellite loci that show some microspatial structuring in the western Atlantic (Ruzzante et al, 1998;Beacham et al, 2000). Microsatellite data are not available for Faroese cod.…”

Environmental variables, habitat discontinuity and life history shaping the genetic structure of Pomatoschistus marmoratus

“…However, nuclear DNA markers (microsatellites) are diploids, with biparental inheritance. This leads to the expectation that more genetic variability and population differentiation would be detected with nuclear markers (Ruzzante et al 1998). In fact, our microsatellite results supported this expectation, showing higher values of effective population size and lower rates of gene flow in contrast to our previous mitochondrial data ( Vergara-Chen et al 2010a).…”

Mito-nuclear discordance in the degree of population differentiation in a marine goby

“…Geographical and climatic factors acting during the Pleistocene glaciations (1800-11.5 ka) are the major factors responsible for the present genetic structure of most extant marine species (Hewitt, 2000). Heterogeneity in the marine environment owing to the influence of climate, hydrodynamics and topography, together with biological traits, such as sex-dependent migration, phylopatry and assortative mating, which may counteract gene flow, enhance genetic structuring (Ruzzante et al, 1998).…”