Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada.
Institut de Biologie Intégrative et des Systèmes, Université Laval, Québec, QC, Canada.
Mol Ecol. 2018 May;27(10):2347-2364. doi: 10.1111/mec.14589.
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 = 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 = .49) than geographic distance (IBD) (R = .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.
海洋种群通常具有较弱的遗传分化，因为长距离扩散的潜力促进了高水平的基因流动。然而，水体的强烈定向平流或保留的水动力可以影响海洋种群之间遗传交换的程度。为了确定高度扩散的海洋无脊椎动物——加利福尼亚巨型海参（Parastichopus californicus）遗传结构的海洋学驱动因素，我们首先测试了东北太平洋北美的海岸线上是否存在遗传不连续性。然后，我们检验了两个关于影响种群结构的空间过程的假设：（i）距离隔离（IBD：遗传结构由地理距离解释）和（ii）阻力隔离（IBR：遗传结构由海洋环流驱动）。使用 RADseq，我们对来自 24 个采样地点的 717 个个体进行了基因型分析，这些个体分布在 2719 个中性 SNP 上，以评估种群分化程度，并整合遗传变异估计值与由洋流介导的幼虫扩散的生物物理模型推断的连通概率。我们确定了两个集群，将北部和南部地区分开，并且在地区内存在显著的（尽管较弱）亚结构（F = 0.002，p = 0.001）。在对洋流的非对称性质进行建模后，我们证明了局部海洋学（IBR）是遗传变异的更好预测指标（R = 0.49），而不是地理距离（IBD）（R = 0.18），并且定向过程在塑造细尺度结构方面起着重要作用。我们的研究有助于增加识别海洋系统中显著种群结构的文献，并对加利福尼亚海参和其他受捕捞海洋物种的空间管理具有重要意义。
