Low connectivity and declining genetic variability along a depth gradient in Corallium rubrum populations

This study examines the possible effect of depth on the connectivity and genetic variability in red coral (Corallium rubrum; Octocorallia: Alcyonacea) populations. Patterns of genetic structuring along a depth gradient (from 20 to 70 m) were investigated in two locations of the western Mediterranean coast (northern Catalan and eastern Ligurian Seas) using 10 microsatellite loci. Strong patterns of genetic structuring among the samples were found both within and between the two study sites. In both locations, consistent patterns of reduction in genetic variability along the depth gradient were also observed, suggesting that depth has an important role in determining the patterns of genetic structure in Corallium rubrum. Moreover, a threshold in connectivity was observed among the samples collected across 40–50 m depth, supporting the hypothesis that discrete shallow- and deep-water red coral populations occur. This finding has major implications for management strategies and the conservation of commercially exploited deep red coral populations.