Local selection and population structure in a deep-sea fish, the roundnose grenadier (Coryphaenoides rupestris)

Abstract

Local populations within a species can become isolated by stochastic or adaptive processes, though it is most commonly the former that we quantify. Using presumably neutral markers we can assess the time-dependent process of genetic drift, and thereby quantify patterns of differentiation in support of the effective management of diversity. However, adaptive differences can be overlooked in these studies, and these are the very characteristics that we hope to conserve by managing neutral diversity. In this study, we used 16 hypothetically neutral microsatellite markers to investigate the genetic structure of the roundnose grenadier in the North Atlantic. We found that one locus was a clear outlier under directional selection, with F(ST) values much greater than at the remaining loci. Differentiation between populations at this locus was related to depth, suggesting directional selection, presumably acting on a linked locus. Considering only the loci identified as neutral, there remained significant population structure over the region of the North Atlantic studied. In addition to a weak pattern of isolation by distance, we identified a putative barrier to gene flow between sample sites either side of the Charlie-Gibbs Fracture Zone, which marks the location where the sub-polar front crosses the Mid-Atlantic Ridge. This may reflect a boundary across which larvae are differentially distributed in separate current systems to some extent, promoting differentiation by drift. Structure due to both drift and apparent selection should be considered in management policy.

Biodiversity Patterns and Processes on the Mid‐Atlantic Ridge

“…Jorde & O.A. Bergstad, unpublished observations), some small -scale structure across a putative boundary (the sub -polar front), and evidence for selection associated with depth (White et al 2010 ). In general the comparative studies highlight the importance of several key factors ( Demersal fi shes in general have low resilience to population disturbance, with a population doubling time on the order of 10 years.…”

Genomics of habitat choice and adaptive evolution in a deep-sea fish

“…It has a spawning season peaking in autumn 11 (recent observations were in September at 1,500 m; ref. 12 ), preys on fish, cephalopods and invertebrates in both benthic and pelagic habitats 13 , and shows minor genetic differentiation across its geographic range [14][15][16] .Adaptation to habitat can occur among populations within a species, and if disruptive selection is associated with assortative mating has the potential to promote incipient speciation through ecological processes in sympatry 17 . When environmental change exposes new habitats and niche potential, adaptive radiations may rapidly generate a new lineage of species 18,19 .…”

“…It has a spawning season peaking in autumn 11 (recent observations were in September at 1,500 m; ref. 12 ), preys on fish, cephalopods and invertebrates in both benthic and pelagic habitats 13 , and shows minor genetic differentiation across its geographic range [14][15][16] .…”

Genetic panmixia and demographic dependence across the North Atlantic in the deep-sea fish, blue hake (Antimora rostrata)

“…Including loci under selection can sometimes distort population genetic analyses (White et al, 2010). Therefore, we used a Bayesian approach to detect loci under selection, implemented in the program BAYESCAN (Foll and Gaggiotti, 2008).…”

“…We also conducted analysis of molecular variance in ARLEQUIN 3.1 (Excoffier et al, 2005), with several different hierarchical structures relating to barriers that are thought or known to influence gene flow (White et al, 2010). First, sample sites were grouped according to the side of the sub-polar front on which they fell (north vs south).…”