Michele Barbieri

New records of the pygmy mussel Xenostrobus securis (Bivalvia: Mytilidae) in brackish-water biotopes of the western Mediterranean provide evidence of its invasive potential

The present study reports new records of the invasive pygmy mussel Xenostrobus securis in six brackish-water localities in the western Mediterranean. Until now X. securis , whose native range includes southern Australia and New Zealand, was also known from the northern Adriatic Sea and southern France. Along the coast of northern Tuscany (Italy) X. securis invaded brackish-water canals in the area between the port of Leghorn and the mouth of the Arno River. Moreover, this mussel has been found in one inner site of the Gulf of Olbia (north-eastern Sardinia, Italy) and at the mouth of the Fluvia River (northern Catalonia, Spain). As an ecosystem engineer, X. securis is an ecologically important species, heavily altering pre-existing benthic communities. Given that its presence in other western Mediterranean sites is highly possible, we recommend a closer monitoring of brackish-water biotopes.

Phylogeographical pattern of Euplotes nobilii, a protist ciliate with a bipolar biogeographical distribution.

Nuclear (18S and ITS) and mitochondrial (16S) ribosomal RNA gene sequences were determined from genetically distinct wild‐type strains of Antarctic (nine strains), Fuegian (four strains), Greenland (nine strains) and Svalbard (three strains) populations of the marine ciliate, Euplotes nobilii, and analysed for their nucleotide polymorphisms. A close genetic homogeneity was found within and between the Antarctic and Fuegian populations, while more significant levels of genetic differentiation were detected within and between the two Arctic populations, as well as between these populations and the Antarctic/Fuegian ones. The phylogeographical pattern that was derived from these data indicates that gene flow is not limited among Arctic populations; it equally connects the Arctic and Antarctic populations either directly, or through the Fuegian population. This indication reinforces previous evidence from laboratory assays of mating interactions between some of the strains analysed in this work that Southern and Northern polar populations of E. nobilii belong to a unique, panmictic population that substantially share the same gene pool.

A contribution to the phylogeography of Pinctada imbricata radiata (Leach, 1814) (Bivalvia: Pteriidae) from the Eastern Mediterranean Sea by means of the mitochondrial COI marker.

Abstract Pinctada imbricata radiata (Leach, 1814) was the first Lessepsian bivalve reported in the Mediterranean Sea where it is progressively expanding westward. Its native range includes the Indian Ocean and western Atlantic. The present study provides the first insight into the species’ phylogeographic structure, by analysing sequences of a 385-bp region of the mitochondrial gene coding for the subunit I of the cytochrome c oxydase (COI). Sixty-four individuals collected at seven Mediterranean localities were sequenced; in addition, eight COI sequences of individuals from the species’ native range (Persian Gulf) were retrieved from GenBank. Overall, we detected 10 haplotypes. Samples from both the native range and invaded localities were characterised by low levels of haplotype and nucleotide diversity (total h = 0.351, total π = 0.0013). Significant genetic divergence was found between Persian Gulf and Mediterranean Sea samples, whereas very shallow genetic structuring was observed within the Mediterranean study area. Moreover, no pattern of isolation by distance was detected in the Mediterranean. From a historical demography perspective, our results on Mediterranean samples were consistent with a very recent, or even ongoing, demographic expansion. Range expansion of exotic thermophilic species in this area is a widely observed phenomenon that many authors have related to global warming.

Distribution of natural populations of the killifish Aphanius fasciatus (Valenciennes, 1821) (Teleostei: Cyprinodontidae) in Italy: past and current status, and future trends

Abstract The census of natural populations provides relevant information for both conservation purposes and environmental monitoring. In the present work, natural populations of the killifish Aphanius fasciatus (Teleostei: Cyprinodontidae) were censused in the Italian territory. The historical distribution of the species was reconstructed with the aid of bibliographic material and museal samples, in order to evaluate the extent of changes in its distribution. Three periods (pre-1990s, 1990s, post-1990s) and five habitat types (lagoons/coastal ponds, saltworks, canals, river mouths, inland water bodies) were considered. Overall, we recorded the presence of A. fasciatus in 82 localities, the majority of which are lagoons/ponds. The species showed a widespread decline and sometimes local population extinction, due to habitat degradation and competition with the introduced poeciliid Gambusia holbrooki. With a few exceptions, A. fasciatus is currently extinct in inland waters, being mainly present in coastal brackish-water habitats. The occurrence of stable populations along the central Tyrrhenian, northern Adriatic, Sardinian and Apulian coastal biotopes is confirmed. The populations of Sicilian inland waters, considered extinct, showed recovery capabilities. In northern Tuscany, where the species was also considered extinct, there are also recent records. From a temporal perspective, the present work shows that A. fasciatus experienced population reductions throughout its range in the 1990s, when the species appeared locally extinct, or strongly rarefied, in several localities. Since then, the species recovered in the majority of the native range. However, careful monitoring is needed in order to control the effects of habitat alterations and competition with G. holbrooki on natural populations of A. fasciatus. Given the importance of brackish-water habitats as both biodiversity hotspots and buffer areas against rainfalls and floods, A. fasciatus may be raised to the status of “umbrella species” with regard to these habitats.