Journal
MOLECULAR ECOLOGY
Volume 27, Issue 10, Pages 2347-2364Publisher
WILEY
DOI: 10.1111/mec.14589
Keywords
asymmetric eigenvector maps; marine connectivity; population genomics; RAD sequencing; sea cucumber; seascape genetics
Funding
- Natural Sciences and Engineering Research Council of Canada [5134, D3-460408-2014, STPGP 4307062012]
- Fisheries and Oceans Canada (DFO)
- Program for Aquaculture Regulatory Research (PARR)
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Marine populations are typically characterized by weak genetic differentiation due to the potential for long-distance dispersal favouring high levels of gene flow. However, strong directional advection of water masses or retentive hydrodynamic forces can influence the degree of genetic exchange among marine populations. To determine the oceanographic drivers of genetic structure in a highly dispersive marine invertebrate, the giant California sea cucumber (Parastichopus californicus), we first tested for the presence of genetic discontinuities along the coast of North America in the northeastern Pacific Ocean. Then, we tested two hypotheses regarding spatial processes influencing population structure: (i) isolation by distance (IBD: genetic structure is explained by geographic distance) and (ii) isolation by resistance (IBR: genetic structure is driven by ocean circulation). Using RADseq, we genotyped 717 individuals from 24 sampling locations across 2,719 neutral SNPs to assess the degree of population differentiation and integrated estimates of genetic variation with inferred connectivity probabilities from a biophysical model of larval dispersal mediated by ocean currents. We identified two clusters separating north and south regions, as well as significant, albeit weak, substructure within regions (F-ST = 0.002, p = .001). After modelling the asymmetric nature of ocean currents, we demonstrated that local oceanography (IBR) was a better predictor of genetic variation (R-2 = .49) than geographic distance (IBD) (R-2 = .18), and directional processes played an important role in shaping fine-scale structure. Our study contributes to the growing body of literature identifying significant population structure in marine systems and has important implications for the spatial management of P.californicus and other exploited marine species.
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