Data from: Asymmetric oceanographic processes mediate connectivity and population genetic structure as revealed by RADseq in a highly dispersive marine invertebrate (Parastichopus californicus)

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 (FST = 0.002, p = 0.001). After modeling the asymmetric nature of ocean currents, we demonstrated that local oceanography (IBR) was a better predictor of genetic variation (R2 = 0.48) than geographic distance (IBD) (R2 = 0.17) 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.

海洋种群通常表现出较弱的遗传分化，这是因为长距离扩散潜力有利于高水平的基因交流。然而，水团的强方向平流或滞留性水动力作用力可影响海洋种群间的基因交流程度。为探究高度扩散性海洋无脊椎动物——加利福尼亚巨海参（*Parastichopus californicus*）遗传结构的海洋学驱动因子，我们首先在东北太平洋的北美沿岸区域检测了遗传不连续性的存在。随后我们针对影响种群结构的空间过程验证了两项假说：（1）距离隔离（isolation-by-distance, IBD）：遗传结构由地理距离解释；（2）阻力隔离（isolation-by-resistance, IBR）：遗传结构由海洋环流驱动。本研究利用限制性位点关联测序（RADseq）技术，对覆盖2719个中性单核苷酸多态性（SNP）位点的24个采样点的717个个体进行基因分型，以评估种群分化程度；同时将遗传变异评估结果与海洋环流介导的幼虫扩散生物物理模型所推断的连通性概率进行整合。我们鉴定出了区分南北区域的两个遗传簇，同时在区域内部检测到了虽弱但显著的亚结构（FST=0.002，p=0.001）。在对洋流的非对称性进行建模后，我们证实相较于地理距离（距离隔离，IBD，R²=0.17），局地海洋环境（阻力隔离，IBR，R²=0.48）能更好地预测遗传变异，且方向过程在塑造精细尺度种群结构中发挥了重要作用。本研究丰富了当前关于海洋系统中显著种群结构的相关文献，并为加利福尼亚巨海参（*Parastichopus californicus*）及其他被开发利用的海洋物种的空间管理提供了重要参考。