Complex genetic structure revealed in the circum-Antarctic broadcast spawning sea urchin Sterechinus neumayeri

Patterns and mechanisms of gene flow and larval dispersal in the Antarctic marine environment are still poorly understood, despite the current threat of rapid climate change and the need for such information to inform conservation and management efforts. Studies on Antarctic brooding marine invertebrates have demonstrated limited connectivity, concurrent with life history expectations; however, no equivalent data are available for broadcast spawning species for which we might expect a higher capacity for larval dispersal. Here, we have used microsatellite DNA markers and mitochondrial DNA sequence data to explore patterns of genetic structure and infer larval dispersal patterns across spatial scales of <500 m to 1400 km in the broadcast spawning sea urchin Sterechinus neumayeri. We show genetic differentiation at small spatial scales (<1 km), but genetic homogeneity over moderate (1−25 km) and large spatial scales (1000 km), consistent with patterns described as chaotic genetic patchiness. Self-recruitment appears common in S. neumayeri, and genotypes of larvae collected from the water column provide preliminary evidence that the adult population structure is maintained through variability among larval cohorts. Genetic similarity at large spatial scales may represent evolutionary connectivity on a circum-Antarctic scale, and likely also reflects a history of shelf recolonisation after isolation in glacial refugia.