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.