Mitochondrial DNA of Sardinian and North-West Italian Populations Revealed a New Piece in the Mosaic of Phylogeography and Phylogeny of Salariopsis fluviatilis (Blenniidae)

SIMPLE SUMMARY: The present study provides new molecular data on populations of the freshwater blenny Salariopsis fluviatilis from Italian geographic areas (north-western regions and Sardinia Island) so far never investigated and uses five species delimitation methods in order to shed further light on the Mediterranean phylogeography of this fish and give a more comprehensive scenario of its taxonomic status. Our findings clarified the phylogeographical patterns of the northern Italian populations of Salariopsis fluviatilis sensu stricto, considering the Po River basin and some Tyrrhenian basins of the Liguria region on the other side of the Ligurian Alps. The dispersal pathways of the island of Sardinia were also investigated suggesting that patterns of genetic structuring for this species are probably linked to Pleistocene glacial and interglacial periods. Results obtained supported previous studies in evidencing the occurrence of a species complex for Salariopsis fluviatilis with at least three taxonomic units: Salariopsis fluviatilis sensu stricto, Salariopsis cf. fluviatilis diffused in the Middle East and a further taxonomic entity from the Iberian Guadiana River basin whose tributaries flow in the Atlantic Ocean. For what concerns Salariopsis fluviatilis sensu stricto, two divergent groups of populations were reported in the present study, being the first diffused in western Mediterranean areas and the second in western Adriatic and eastern Mediterranean areas. ABSTRACT: The genus Salariopsis (Blenniidae) comprises freshwater blenny fish that inhabits Mediterranean Sea, Black Sea, and north-east Atlantic areas. Three species were formally described to date: Salariopsis fluviatilis. S. economidisi, and S. atlantica. In this study, 103 individuals were collected from different Italian regions (Sardinia, Liguria, Piedmont, Lombardy) and analyzed using the mtDNA Control Region and the ribosomal 16s gene. We aimed (i) to depict the phylogeographic patterns of S. fluviatilis in northern Italy and Sardinia and (ii) to compare the genetic structure of Italian samples with those from other Mediterranean regions. Results obtained showed the presence of a well-supported genetic structuring among Italian S. fluviatilis populations, shedding new light on the phylogeographic patterns of northern Italian populations of S. fluviatilis sensu stricto across the Ligurian Alpine ridge and the Sardinia Island-mainland dispersal patterns. Furthermore, our species delimitation analysis was consistent in supporting results of previous research about the presence of genetic differentiation among S. fluviatilis, evidencing: (i) a large group of S. fluviatilis sensu stricto that includes two sub-groups (Occidental and Oriental), (ii) one group comprising populations from the Middle East of a taxonomic entity corresponding to Salariopsis cf. fluviatilis, and (iii) one group of Iberian individuals from the Guadiana River.