The red coral Corallium rubrum has a long history of intensive exploitation. As a consequence,most populations have been overharvested, which may be leading to reduced levels ofgenetic diversity. C. rubrum is a gorgonian distributed in the Mediterranean Sea and along theneighbouring Atlantic coasts, with brooding larvae which disperse only over short distances. Suchlimited dispersal of larvae suggests that gene flow is restricted in this species, but no experimentalevidence is yet available. In the present study, small spatial scale genetic structuring was analysed inC. rubrum samples collected in the Ligurian Sea using a hierarchical sampling design, includingscales from 10s to 100s of metres. The genetic variation of each colony was analysed using 4 microsatelliteloci. Significant deviations from Hardy-Weinberg equilibrium due to elevated heterozygotedeficiencies were detected in all samples and were consistent with the occurrence of inbreeding anda Wahlund effect. Significant levels of genetic differentiation were found both between locations(FST = 0.209 ± 0.02) and among samples within each location (FST range = 0.025 to 0.082). Our resultsindicate the occurrence of significant genetic structuring at spatial scales of 10s of metres, supportingthe hypothesis that planulae have a limited effective dispersal ability. The occurrence of structuredbreeding units and differences in genetic diversity among samples also suggest that strategies forsustainable management and conservation of red coral should be defined at a local scale.
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