Abstract
While shallow water red coral populations have been overharvested in the past, nowadays, commercial harvesting shifted its pressure on mesophotic organisms. An understanding of red coral population structure, particularly larval dispersal patterns and connectivity among harvested populations is paramount to the viability of the species. In order to determine patterns of genetic spatial structuring of deep water Corallium rubrum populations, for the first time, colonies found between 58–118 m depth within the Tyrrhenian Sea were collected and analyzed. Ten microsatellite loci and two regions of mitochondrial DNA (mtMSH and mtC) were used to quantify patterns of genetic diversity within populations and to define population structuring at spatial scales from tens of metres to hundreds of kilometres. Microsatellites showed heterozygote deficiencies in all populations. Significant levels of genetic differentiation were observed at all investigated spatial scales, suggesting that populations are likely to be isolated. This differentiation may by the results of biological interactions, occurring within a small spatial scale and/or abiotic factors acting at a larger scale. Mitochondrial markers revealed significant genetic structuring at spatial scales greater then 100 km showing the occurrence of a barrier to gene flow between northern and southern Tyrrhenian populations. These findings provide support for the establishment of marine protected areas in the deep sea and off-shore reefs, in order to effectively maintain genetic diversity of mesophotic red coral populations.
Highlights
Corallium rubrum (L.1758), known as precious red coral, is a gorgonian endemic to the Mediterranean Sea and Eastern Atlantic Ocean occurring as a large numbers of small sized colonies above 50 m depth ([1], hereafter named shallow-water populations), or as scattered larger colonies below 50 m down to the deeper margin of its distribution ([2], hereafter named deep-water populations)
Specimens sharing the same MLG showed identical mtMSH and mitochondrial control region (mtC) sequences. Both these results suggest that shared genotypes derive from fragmentation of single individual colonies, and were included only once, obtaining a final data set of 135 different multilocus genotypes (Table 1)
The three molecular markers used in this study provided different estimates of genetic differentiation among populations
Summary
Corallium rubrum (L.1758), known as precious red coral, is a gorgonian endemic to the Mediterranean Sea and Eastern Atlantic Ocean occurring as a large numbers of small sized colonies above 50 m depth ([1], hereafter named shallow-water populations), or as scattered larger colonies below 50 m down to the deeper margin of its distribution ([2], hereafter named deep-water populations). Red coral harvesting affected mainly shallow water populations that were accessed by traditional methods. In an effort to protect these endangered populations, recommendations made on 2011 by the FAO-GFCM Scientific Committee were adopted by imposing a ban of red coral harvesting at depths shallower 50 m [7]. Declining availability of colonies coupled with the enforcement of the aforementioned regulations pushed red coral fishermen to harvest deeper populations found within the mesophotic biogenic reefs (50–150 m depth; [3]). Provide sound background scientific knowledge on the functioning of red coral mesophotic populations as well as on their relationship with shallow ones become a priority for the implementation of effective management and conservation policies
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