Mesophotic red coral populations: genetic variability and connectivity
Nome e Cognome
Rosa Angela Pugliese
Contatto
campusravenna.segdidaambientemare@unibo.it
Relatore/Correlatore
Prof.Abbiati Marco
Dott.ssa Costantini Federica
Ente e Laboratorio di Ricerca
Abstract
The Mediterranean red coral (Corallium rubrum, L. 1758) is a long living octocoral that has been commercially harvested since ancient time for its red axial calcitic skeleton. At present, shallow-water red coral populations are overexploited and consequently in decline, so deeper populations below 50m (mesophotic populations) have currently become the most commercially harvested. Unfortunately, very little is known about the biology and ecology of these mesophotic populations and for their management and conservation a better understanding of their genetic structuring and connectivity is needed. The present study was carried out to define genetic variability and structuring in Corallium rubrum populations located between 60 and 120 metres depth, collected in three different areas of the Tyrrhenian Sea (Liguria, Toscana and Campania). A total of fourteen populations were sampled and analyzed by means of a set of 10 nuclear microsatellite loci and the putative control region of the mitochondrial DNA (MtC). Microsatellite genotyping indicated that all loci were polymorphic and showed significant deviations from Hardy–Weinberg equilibrium, due to an heterozygote deficiency, probably related to the presence of null alleles and/or inbreeding, as was previously observed in shallow-water populations. Both types of molecular markers showed high genetic similarity between Liguria and Toscana populations (Northern Tyrrhenian) compared to Campania populations (Southern Tyrrhenian). The genetic differentiation observed between North and South Tyrrhenian populations follows a weak but significant pattern of isolation by distance. However, low correlation between genetic divergence and geographic distances detected using the mitochondrial marker suggests that observed patterns could also be partially related to the presence of a long term barrier to gene flow, given the hydrodynamic and geological characteristic of the studied area. At smaller spatial scales (within areas) the two molecular markers indicate different structures, probably due to the low polymorphism of MtC or to the occurrence of some historical links within regions. These results show that mesophotic red coral populations are mainly self recruiting, similarly to the shallow water ones, with a limited effective dispersal ability of the larvae, further enhanced by the patchy distribution of suitable habitats. According to our results, management strategies of red coral harvesting in the mesophotic habitats should be defined at a regional level, being highly advisable the creation of deep-sea marine protected areas, in order to maximise the genetic diversity of this highly vulnerable populations of red coral in this unique habitats.
