Molecular taxonomy and specific diversity of Mediterranean museum collections of ancient sawfish's finds (Chondrichthyes, Pristidae)

Human impact has led to degradation of different marine ecosystems, especially coastal, estuary and river environments, causing the decline of many marine fish populations. Among elasmobranchs one of the most threatened ones are sawfishes (Chondrichthyes, Pristidae), resulting extinct in many coastal areas around the world. In the Mediterranean Sea they occurred with two species, Pristis pristis and P. pectinata, until the second half of the last century. To better understand the baselines and the past distribution of sawfish populations, historical rostra available in the museum collections demonstrated to be value resource. This study aimed to identify new short genetic markers and a new functional amplification protocol suitable for the specific identification of ancient sawfish’s finds. A total of 78 rostra specimens, dated 1700-1900 and catalogued as unknown or Mediterranean origin, were collected from 10 European museums and were properly prepared for ancient DNA genetic analysis. Small fragments (118-266bp) of the mitochondrial COI and the NADH2 genes resulted to be useful for the taxonomic identification of 69 rostra at the species level. All the analyses computed in this study, NJ tree reconstruction, Automatic Barcode Gap Discovery, Characteristic Attribute analysis and P-distance computed between species, showed in full concordance the identification of four sawfish species: P. pristis, P. zijsron, P. pectinata and Anoxypristis cuspidata. A high frequency of mismatches was found between molecular identification and species museum cataloguing, especially between P. pectinata and P. zijsron (72%). Specimens were identified mostly as P. zijsron, even among Mediterranean samples and the presence of two sequence sub-clusters was highlighted in this poorly barcoded species. In conclusion, this new knowledge requires further investigations on the structure of sawfish populations and on their evolutionary dynamics to identify a suitable conservation policy.