The big-scale sand smelt Atherina boyeri lives in fresh water, brackish water and sea water of the western Atlantic Ocean and Mediterranean Sea. Previous studies concerning distribution, biometric characters and genetic molecular markers have suggested the possible existence of two or even three different groups or species of sand smelt, one 'lagoon' type and one (or twopunctuated and non-punctuated on the flanks) 'marine' type. In this study, the presence and the localization of an insertion was described, c. 200 bp in length, in the mtDNA of the lagoon and marine punctuated specimens of A. boyeri and its absence in the marine non-punctuated specimens, as well as in other two congeneric species, Atherina hepsetus and Atherina presbyter, and in the atheriniform Menidia menidia. The intergenic spacer is located between the tRNA Glu and cytochrome b (cyt b) genes and shares a c. 50% sequence similarity with cyt b. The distribution and the features of the intergenic spacer suggest that it might have originated from an event of gene duplication, which involved the cyt b gene (or, more likely, a part of it) and which took place in the common ancestor of the lagoon and the marine punctuated specimens. The data obtained therefore support the hypothesis of the existence of three cryptic and, or sibling species within the A. boyeri taxon and provide a genetic molecular marker to distinguish them.

Franchini, P., Sola, L., Crosetti, D., Milana, V., and Rossi, A. R. 2012. Low levels of population genetic structure in the gilthead sea bream, Sparus aurata, along the coast of Italy. – ICES Journal of Marine Science, 69: 41–50. The gilthead sea bream, Sparus aurata, is a coastal, commercially important fish. Contrasting results concerning the genetic structure of the species at different geographic scales have been reported. Here, an investigation is made into the population genetic structure of S. aurata along the coast of Italy, using samples analysed previously and material from new sampling sites (12) and using different microsatellite loci (10). One sample from the eastern Atlantic and three temporal replicates from one site were also included. The presence of a weak (overall FST = 0.0072), but significant, genetic population subdivision was detected by F-statistics. Temporal replicates indicate genetic data consistency over time. Isolation by distance between the Atlantic and the coast of Italy is suggested by a Mantel test. The distributional pattern of genetic variance obtained by analysis of molecular variation reflects the geographic sampling areas, but is only partially congruent with the results obtained with fewer sites and loci. The dispersal of passive eggs/larvae by the main currents appears to contribute to shaping the gene flow. Given the intensity of sea bream aquaculture activities in Italy, the possibility that aquaculture may have partially contributed to the population genetic pattern detected cannot be excluded.

Karyotype and other chromosomal characteristics of the Appenine endemic cyprinid fish, Toscana stream chub Squalius lucumonis, were analysed using conventional banding and FISH with 45S and 5S rDNA probes. The diploid chromosome number (2n = 50) and karyotype characteristics including pericentromeric heterochromatic blocks and GC-rich CMA(3)-positive sites corresponding to both positive Ag-NORs and 45S rDNA loci on the short arms of a single medium-sized submetacentric chromosome pair were consistent with those found in most European leuciscine cyprinids. On other hand, 5S rDNA FISH in the Toscana stream chub and three other Italian leuciscines, S. squalus, Rutilus rubilio and Telestes muticellus, revealed a species-specific hybridization pattern, i.e. signals on four (S. lucumonis), three (S. squalus and R. rubilio) and two (T. muticellus) chromosome pairs. Whereas all the species shared the 5S rDNA loci on the largest subtelocentric chromosome pair, a "leuciscine" cytotaxonomic marker, S. lucumonis showed both classes of rDNA loci tandem aligned on the short arms of chromosome pair No. 12. The present findings suggest that the observed high variability of 5S rDNA loci provides a powerful tool for investigation of karyotype differentiation in karyologically conservative leuciscine fishes.

Recent molecular phylogenetic analyses have shown that the Mugil curema Valenciennes, 1836 species complex includes M. incilis Hancock, 1830, M. thoburni (Jordan & Starks, 1896) and at least four “M. curema” mitochondrial lineages, considered as cryptic species. The cytogenetic data on some representatives of the species complex have shown a high cytogenetic diversity. This research reports the results of cytogenetic and molecular analyses of white mullet collected in Ecuador. The analyzed specimens were molecularly assigned to the Mugil sp. O, the putative cryptic species present in the Pacific Ocean and showed a 2n = 46 karyotype, which is composed of 2 metacentric and 44 subtelocentric/acrocentric chromosomes. This karyotype is different from the one described for M. incilis (2n = 48) and from those of the two western Atlantic lineages Mugil curema (2n = 28), and Mugil margaritae (2n = 24). Data suggest the need for a morphological analysis to assign a species name to this Pacific lineage.

Groups of proximate continental islands may conceal more tangled phylogeographic patterns than oceanic archipelagos as a consequence of repeated sea level changes, which allow populations to experience gene flow during periods of low sea level stands and isolation by vicariant mechanisms during periods of high sea level stands. Here, we describe for the first time an ancient and diverging lineage of the Italian wall lizard Podarcis siculus from the western Pontine Islands. We used nuclear and mitochondrial DNA sequences of 156 individuals with the aim of unraveling their phylogenetic position, while microsatellite loci were used to test several a priori insular biogeographic models of migration with empirical data. Our results suggest that the western Pontine populations colonized the islands early during their Pliocene volcanic formation, while populations from the eastern Pontine Islands seem to have been introduced recently. The inter-island genetic makeup indicates an important role of historical migration, probably due to glacial land bridges connecting islands followed by a recent vicariant mechanism of isolation. Moreover, the most supported migration model predicted higher gene flow among islands which are geographically arranged in parallel. Considering the threatened status of small insular endemic populations, we suggest this new evolutionarily independent unit be given priority in conservation efforts.

Italian native populations of Mediterranean brown trout belong to the Salmo trutta complex. This species complex includes many mitochondrial lineages and phenotypes that have caused taxonomic controversies over time. The spatial distribution and the genetic diversity of these fishes are threatened by habitat destruction, global warming and, mainly, by the introduction of domestic trout of Atlantic origin. Indeed allochthonous trouts were massively restocked in Italian rivers for a century and they admixed with native populations. In order to identify residual native populations of Mediterranean brown trout, a genetic analysis of specimens collected within Latium region, on the Tyrrhenian slope of central Italy, was undertaken. To this purpose, 210 trout specimens were collected from six different rivers and analyzed for the identification of their nuclear (LDH-C1* RFLP) and mitochondrial (Control Region sequences) genotypes. Genetic characterization with these molecular markers allowed a quantitative estimate of allochthonous genotypes, which are present in all brown trout populations of the six sites, even if not equally distributed across the sampling area. At least three populations, inhabiting diverse lotic ecosystems (mountain, hilly and coastal streams respectively), are characterized by a high percentage of native nuclear allele *100 at locus LDH-C1* and typical Mediterranean haplotypes (of AD and ME lineages), which can be considered as different management units (MUs). This finding highlighted the aquatic ecosystems of the Latium Region as an important hotspot of salmonid biodiversity within the Italian peninsula, with important implications from a conservation perspective.

Leuciscine fishes represent an important component of freshwater ichthyofauna endemic to northern Mediterranean areas. This lineage shows high intra-specific morphological variability and exhibits high levels of hybridization, two characteristics that contribute to systematic uncertainties, misclassification of taxa and, potentially, the mismanagement of biodiversity. This study focused on brook chub, Squalius lucumonis, an endemic taxon of Central Italy. The taxonomic status of this species has long been questioned, and a hybrid origin from sympatric leusciscines (S. squalus x Rutilus rubilio, or S. squalus x Telestes muticellus) has been hypothesised. A phenotypic (evaluating shape and meristic counts) and genetic (using mitochondrial and nuclear markers) investigation of these four taxa was conducted to test species delimitation in sympatric areas and to evaluate the taxonomic status of S. lucumonis. One hundred and forty-five individuals of all four taxa were collected within streams of the lowest portion of the Tiber River basin and analysed; this region encompasses a large portion of the S. lucumonis distribution. The different morphological and genetic approaches were individually examined, compared, and then combined in a quantitative model to both investigate the limits of each approach and to identify cases of misclassification. The results obtained confirm the cladogenetic non-hybrid origin of S. lucumonis, highlight the need for immediate conservation actions and emphasise the value of an integrated approach in the study of leuciscines evolution.

Atherina boyeri is a common inhabitant of the Mediterranean brackish and coastal waters. Several recent studies proposed the recognition of three distinct forms/species (one lagoon/freshwater and two marine) within an A. boyeri complex. In this study, we used 10 newly available microsatellite loci to better define the genetic structure of the lagoon form. A total of 428 fishes from 11 lagoons along the Italian and Albanian coasts and three Italian lakes were analyzed. A pronounced genetic spatial structure was confirmed for all considered geographic scales (near, medium and broad). A restricted gene flow was detected, suggesting reduced population connectivity. The comparison of present data and previous studies, based on mtDNA and RAPD markers, allowed a preliminary identification of the roles of recent factors (gene flow, habitat discontinuity and water currents) and past events (e.g., Pleistocene glaciations) in shaping the pattern of genetic differentiation