New insights into connectivity patterns of mesophotic red coral (Corallium rubrum) populations

We investigated the genetic diversity and connectivity patterns of mesophotic Corallium rubrum populations (from a depth of 87 to 107 m) near Sardinia (Western Mediterranean Sea) using microsatellite data. Firstly, we tested the hypotheses that (1) mesophotic areas represent ‘thermal and/or reproductive refugia†for the species, and (2) strong genetic breaks separate the coral populations of the different sub-basins of the Western Mediterranean Sea. Secondly, we aimed to examine the impact of harvesting on the genetic features of populations. Genetic analyses pointed out the occurrence of significant genetic differentiation (overall FST = 0.115, P value = 0) and an isolation-by-distance pattern. Bayesian assignment analyses revealed four distinct clusters. The differential amplification success of some microsatellite loci along a north–south gradient confirmed the existence of strongly differentiated red coral populations in the Tyrrhenian with respect to the Algero-Provençal Basin. From a management perspective, the high genetic diversity and the substantial demographic stability indicate that Sardinian red coral populations are stable and still sustainably exploited. Nevertheless, the significant spatial structuring at the scale of less than 10 km indicates that they are sustained largely by local recruitment, excluding the possibility that they can help in recovering shallower banks.