No abstract

Rocky pinnacles arising from soft bottoms of the circa-littoral zone may host oases of deepwa- ter coral biodiversity: Engineer species that enhance ecosystem’s three-dimensional complexity often act- ing as shelter for associated fauna that can comprise commercially relevant species. Although variations in beta diversity of these coral oases were recently docu- mented at different spatial scales, information on the role of geomorphogical features of rocky outcrops can be considered mostly an unaddressed issue. To comply with this task, five rocky pinnacles showing different geomorphological features (average slope, ruggedness, sediment accumulation), dwelling between 120 and 170 m depth along south Sardinia continental margin, were investigated by means of ROV imaging. We tested the null hypothesis that coral abundance and diversity [estimated using four black corals (Antipatharia) and seven gorgonians (Alcyonacea) as target species] did not differ among investigated sites. Overall, total coral abundance varied from 1.35 to 7.23 col m2; Callogor- gia verticillata, followed by Eunicella cavolinii and Corallium rubrum were the most abundant gorgonians, while Antipathella subpinnata and Parantipathes larix were the most abundant black corals. Through uni- and multivariate analyses, significant differences in corals biodiversity were identified, allowing us to reject the null hypothesis, emphasizing a remarkable variability in beta diversity, apparently following variations in geo- morphological features of investigated pinnacles. More- over, a visual census of anthropogenic debris revealed that lost fishing gears represented the most frequently observed debris, stressing the need to identify further and more focused strategies of conservation to protect these oases of coral biodiversity

Genetic variation at eight microsatellite loci was studied in nine populations of the blue and red shrimp Aristeus antennatus to investigate whether distinct stocks are present in the Western Mediterranean Sea. A high level of gene flow and no evidence of genetic partitioning were discovered. No significant variation was found (FST = 0.00673, P‐value = 0.067) even when shrimps from exploited and those from deep‐water unexploited grounds were compared. No evidence of reduction or expansion of population size in the recent past was found, as indicated by the bottleneck and interlocus g‐tests. Our results are consistent with previous studies using mitochondrial gene methods and allozymes, indicating that, for this species, extensive pelagic larval dispersal and adult migration are probably responsible for the genetic homogeneity observed. In particular, due to a different bathymetric distribution of males and females, reported to be associated with different water masses and hence with possible differential dispersal capacity between sexes, the hypothesis of sex‐biased dispersal was tested. Mean values of corrected assignment indices and mean relatedness values were higher for males, suggesting that females are the more widely dispersing sex. Molecular assessment of A. antennatus from the Western Mediterranean provides data of biological and evolutionary interest for the successful management of such a highly valuable fishery resource.

The precious coral Corallium rubrum is one of the most vulnerable resources in the Mediterranean Sea because of the high levels of human‐related and natural mortality rates. The aim of the present study was to document the diversity and connectivity patterns among Sardinian Corallium rubrum populations focusing, in particular, on deep populations (>80 m depth) where the commercial exploitation is concentrated. Microsatellite markers revealed high levels of inbreeding, heterozygote deficits, and significant genetic differentiation between and within areas at different depths, with an associated ‘isolation by distance’ pattern. These results indicated that for precious coral populations in Sardinia the ‘deep reef refugia hypothesis’, that envisages the capacity for deep corals to act as seed banks for the shallower impaired (over‐harvested) populations, is not supported. The highest genetic diversity recorded in Sardinia for all areas and depths with respect to other Mediterranean areas indicates that the strict local management has been effective, since harvesting has not yet led to a substantial erosion of the genetic pool. Possible causes for the high levels of observed diversity in Sardinia are discussed in relation to hydrological conditions, its geographical position and its proximity to some putative glacial refugia. Thus, given the occurrence in Sardinia of highly diverse and differentiated deep‐water populations of C. rubrum whose genetic diversity are important for the long‐term resilience of the species, the results of the present study strongly support the close monitoring of harvesting, along with the maintenance or even strengthening of the current management and conservation measures (no‐take protected areas) already in place in the area. Copyright © 2014 John Wiley & Sons, Ltd.