Species identification, distributioin and reproductive interactions of common smoot-hound and blackspotted smooth-hound shark (Genus mustelus) in the Adriatic Sea

Longstanding taxonomic ambiguity and uncertainty exist in the identification of the common (M. mustelus) and blackspotted (M. punctulatus) smooth-hound in the Adriatic Sea. The lack of a clear and accurate method of morphological identification, leading to frequent misidentification, prevents the collation of species-specific landings and survey data for these fishes and hampers the delineation of the distribution ranges and stock boundaries of the species. In this context, adequate species-specific conservation and management strategies can not be applied without risks of population declining and local extinction. In this thesis work I investigated the molecular ecology of the two smooth-hound sharks which are abundant in the demersal trawl surveys carried out in the NC Adriatic Sea to monitor and assess the fishery resources. Ecological and evolutionary relationships were assessed by two molecular tests: a DNA barcoding analysis to improve species identification (and consequently the knowledge of their spatial ecology and taxonomy) and a hybridization assay based on the nuclear codominant marker ITS2 to evaluate reproductive interactions (hybridization or gene introgression). The smooth-hound sharks (N=208) were collected during the MEDITS 2008 and 2010 campaigns along the Italian and Croatian coasts of the Adriatic Sea, in the Sicilian Channel and in the Algerian fisheries. Since the identification based on morphological characters is not strongly reliable, I performed a molecular identification of the specimens producing for each one the cytochrome oxidase subunit 1 (COI) gene sequence (ca. 640 bp long) and compared them with reference sequences from different databases (GenBank and BOLD). From these molecular ID data I inferred the distribution of the two target species in the NC Adriatic Sea. In almost the totality of the MEDITS hauls I found no evidence of species sympatry. The data collected during the MEDITS survey showed an almost different distribution of M. mustelus (confined along the Italian coasts) and M. punctulatus (confined along the Croatian coasts); just one sample (Gulf of Venice, where probably the ranges of the species overlap) was found to have catches of both the species. Despite these data results suggested no interaction occurred between my two target species at least during the summertime (the period in which MEDITS survey is carried out), I still wanted to know if there were inter-species reproductive interactions so I developed a simple molecular genetic method to detect hybridization. This method is based on DNA sequence polymorphism among species in the nuclear ribosomal Internal Transcribed Spacer 2 locus (ITS2). Its application to the 208 specimens collected raised important questions regarding the ecology of this two species in the Adriatic Sea. In fact results showed signs of hybridization and/or gene introgression in two sharks collected during the trawl survey of 2008 and one collected during the 2010 one along the Italian and Croatian coasts. In the case that it will be confirmed the hybrid nature of these individuals, a spatiotemporal overlapping of the mating behaviour and ecology must occur. At the spatial level, the northern part of the Adriatic Sea (an area where the two species occur with high frequency of immature individuals) could likely play the role of a common nursery area for both species.

Genetic patterns in recovered specimens of Caretta caretta from the Adriatic Sea

The Adriatic Sea is considered a feeding and developmental area for Mediterranean loggerhead turtles, but this area is severely threatened by human impacts. In the Adriatic Sea loggerhead turtles are often found stranded or floating, but they are also recovered as by-catch from fishing activities. Nevertheless, information about population structuring and origin of individuals found in the Adriatic Sea are still limited. Cooperation with fishermen and a good network of voluntary collaborators are essential for understanding their distribution, ecology and for developing conservation strategies in the Adriatic Sea. In this study, a comparative analysis of biometric data and DNA sequence polymorphism of the long fragment of the mitochondrial control region was carried out on ninety-three loggerheads recovered from three feeding areas in the Adriatic Sea: North-western, North-eastern and South Adriatic. Differences in turtles body sizes (e.g. Straight Carapace Length) among the three recovery areas and relationship between SCL and the type of recovery were investigated. The origin of turtles from Mediterranean rookeries and the use of the Adriatic feeding habitats by loggerheads in different life-stages were assessed to understand the migratory pathway of the species. The analysis of biometric data revealed a significant difference in turtle sizes between the Southern and the Northern Adriatic. Moreover, size of captured turtles resulted significantly different from the size of stranded and floating individuals. Actually, neritic sub-adults and adults are more affected by incidental captures than juveniles because of their feeding behavior. The Bayesian mixed-stock analysis showed a strong genetic relationship between the Adriatic aggregates and Mediterranean rookeries, while a low pro¬portion of individuals of Atlantic origin were detected in the Adriatic feeding grounds. The presence of migratory pathways towards the Adriatic Sea due to the surface current system was reinforced by the finding of individuals bearing haplotypes endemic to the nesting populations of Libya, Greece and Israel. A relatively high contribution from Turkey and Cyprus to the Northwest and South Adriatic populations was identified when the three sampled areas were analyzed independently. These results have to be taken in account in a conservative perspective, since coastal hazards, affecting the population of turtles feeding in the Adriatic Sea may also affect the nesting populations of the Eastern Mediterranean with a unique genetic pattern.