Oregon Sea Grant

Fine-scale spatial and temporal genomic variation among Dungeness crab Cancer magister larval recruits in the California Current Ecosystem

Abstract: Dynamic marine environments can shape complex spatial and temporal patterns in the population connectivity of marine species, and this is often exemplified in species with long larval phases. In this paper, researchers used a genotyping-by-sequencing (GBS) approach to examine fine-scale spatial and temporal genomic variation among Dungeness crab Cancer magister larval recruits sampled in the California Current Ecosystem.

Specifically, they compared samples collected during expected- and late-season recruitment time periods within two consecutive years (2017 and 2018) at two sites in Oregon, USA (Yaquina Bay and Coos Bay). Evidence was found for high gene flow between the expected- and late-season recruits within each year and at both sites based on 1389 neutral loci. In contrast, strong genetic differentiation was observed between these two groups within each year and at both sites based on variation at two putatively adaptive loci. Contrary to prediction, the magnitude of genetic differentiation between these two seasonal groups was greater in 2017 when the Pacific Decadal Oscillation was stronger, upwelling was weaker, and the spring transition was later. Spatial genetic variation was not observed within 2017 or 2018. Comparing across years, expected- and late-season groups were differentiated at putatively adaptive loci.

Interestingly, strong genetic differentiation was also observed between late-season groups across the years. Researchers found no evidence for cohesive larval dispersal among recruits based on genetic relatedness estimates. Overall, findings provide evidence for high connectivity within Dungeness crab, but suggest that selective pressures and ocean conditions influence the genetic composition of larval recruits both intra- and inter-annually.