Pinna nobilis is the largest endemic Mediterranean marine bivalve. During past centuries, various human activities have promoted the regression of its populations. As a consequence of stringent standards of protection, demographic expansions are currently reported in many sites. The aim of this study was to provide the first large broad-scale insight into the genetic variability of P. nobilis in the area that encompasses the western Mediterranean, Ionian Sea, and Adriatic Sea marine ecoregions. To accomplish this objective twenty-five populations from this area were surveyed using two mitochondrial DNA markers (COI and 16S). Our dataset was then merged with those obtained in other studies for the Aegean and Tunisian populations (eastern Mediterranean), and statistical analyses (Bayesian model-based clustering, median-joining network, AMOVA, mismatch distribution, Tajima’s and Fu’s neutrality tests and Bayesian skyline plots) were performed. The results revealed genetic divergence among three distinguishable areas: (1) western Mediterranean and Ionian Sea; (2) Adriatic Sea; and (3) Aegean Sea and Tunisian coastal areas. From a conservational point of view, populations from the three genetically divergent groups found may be considered as different management units.

The fan mussel, Pinna nobilis, represents the largest bivalve endemic to the Mediterranean Sea. Since 2016, dramatic mass mortality of this species has been observed in several areas. The first surveys suggested that Haplosporidium pinnae (currently considered species-specific) was the main etiological agent, but recent studies have indicated that a multifactorial disease may be responsible for this phenomenon. In this study, we performed molecular diagnostic analyses on P. nobilis, P. rudis, and bivalve heterologous host species from the island of Sardinia to shed further light on the pathogens involved in the mass mortality. The results support the occurrence of a multifactorial disease and that Mycobacterium spp. and H. pinnae are not necessarily associated with the illness. Indeed, our analyses revealed that H. pinnae is not species-specific for P. nobilis, as it was present in other bivalves at least three years before the mass mortality began, and species of Mycobacterium were also found in healthy individuals of P. nobilis and P. rudis. We also detected the species Rhodococcus erythropolis, representing the first report in fan mussels of a bacterium other than Mycobacterium spp. and Vibrio spp. These results depict a complicated scenario, further demonstrating how the P. nobilis mass mortality event is far from being fully understood.

Sheep are thought to have been one of the first livestock to be domesticated in the Near East, thus playing an important role in human history. The current whole mitochondrial genome phylogeny for the genus Ovis is based on: the five main domestic haplogroups occurring among sheep (O. aries), along with molecular data from two wild European mouflons, three urials, and one argali. With the aim to shed some further light on the phylogenetic relationship within this genus, the first complete mitochondrial genome sequence of a Cypriot mouflon (O. gmelini ophion) is here reported. Phylogenetic analyses were performed using a dataset of whole Ovis mitogenomes as well as D-loop sequences. The concatenated sequence of 28 mitochondrial genes of one Cypriot mouflon, and the D-loop sequence of three Cypriot mouflons were compared to sequences obtained from samples representatives of the five domestic sheep haplogroups along with samples of the extant wild and feral sheep. The sample included also individuals from the Mediterranean islands of Sardinia and Corsica hosting remnants of the first wave of domestication that likely went then back to feral life. The divergence time between branches in the phylogenetic tree has been calculated using seven different calibration points by means of Bayesian and Maximum Likelihood inferences. Results suggest that urial (O. vignei) and argali (O. ammon) diverged from domestic sheep about 0.89 and 1.11 million years ago (MYA), respectively; and dates the earliest radiation of domestic sheep common ancestor at around 0.3 MYA. Additionally, our data suggest that the rise of the modern sheep haplogroups happened in the span of time between six and 32 thousand years ago (KYA). A close phylogenetic relationship between the Cypriot and the Anatolian mouflon carrying the X haplotype was detected. The genetic distance between this group and the other ovine haplogroups supports the hypothesis that it may be a new haplogroup never described before. Furthermore, the updated phylogenetic tree presented in this study determines a finer classification of ovine species and may help to classify more accurately new mitogenomes within the established haplogroups so far identified.

Two samples of Aphanius fasciatus collected in the Pilo pond (northern Sardinia, Italy) and in an adjacent pool of small surface area were analysed morphologically (235 individuals) and genetically (a subsample of 58 individuals). The aims of the present study were (i) to test the hypothesis that different predation pressures may be associated with morphological and/or genetic differences between samples from each habitat and (ii) to assess the level of divergence between the two populations. Morphological analysis was based on the relative size of fins because it has been shown to be associated with predation pressure. The relative caudal fin area (caudal fin area/total body surface) was smaller in specimens from the pool, in both males and females, whereas no differences were found for the dorsal and anal fin areas. Caudal fins with higher aspect ratio (fin depth/fin length) were found in fish from the pool but not in the pond, due to a higher fin depth. We hypothesised that specimens from the pool would show smaller caudal fin area, since they are subject to lower predation pressure. Random amplification of polymorphic DNA (RAPD) analysis revealed a relatively high degree of both within-and between-sample genetic heterogeneity. The pond and pool samples exhibited heterozygosities, which did not differ significantly by t-test. Between-sample genetic divergence was highlighted by the coancestry coefficient (h = 0.301 ± 0.059, P < 0.001) and analysis of molecular variance (AMOVA) (variance between sites = 41%, P < 0.001). Genetic divergence between sites with a relatively high genetic diversity within both samples suggested that the population in the pool did not originate from a single colonisation event with a small number of founders. The genetic divergence between the two populations is consistent with their differences in fin size.

Patella ferruginea Gmelin, 1791 is an endangered marine gastropod endemic to the Western Mediterranean. Its range is restricted to the Sardinian-Corsican region (SCR), North Africa, a few scattered sites in Southern Spain, and Sicily. Inter-simple sequence repeat (ISSR) markers and three different mitochondrial DNA (mtDNA) regions, Cytochrome c Oxidase subunit I, 12S (small-subunit ribosomal RNA gene) and 16S (large-subunit ribosomal RNA gene), were used to investigate the presence of genetic population structuring. The mtDNA sequences showed very low levels of genetic differentiation. Conversely, ISSRs showed the presence of two main genetic groups, corresponding to Spain, North Africa and Sicily and the SCR. The SCR was further split into two subgroups. The ISSR results suggest that, on a regional scale, the genetic structure of P. ferruginea is mainly determined by the restriction of gene flow by dispersal barriers. On a more local scale human harvesting may play a crucial role in population structuring by increasing the effect of genetic drift.