Past species diversity and zoogeography of historical sawfishes from the Mediterranean area

The drastic reduction of global sawfish populations boosted intense research efforts on the conservation status and recovery of remaining populations. In the Mediterranean Sea, recent research revealed the historical presence and eventual extinction of two species (Pristis pristis and Pristis pectinata). Here, we implemented a multidisciplinary investigative approach to reconstruct species diversity and composition of past sawfish fauna using 172 historical rostra collected from museums and private collections in the Mediterranean area. The combination of ancient DNA analysis with morphometric techniques allowed the species identification of all dried rostra and their assignment to Pristis zijsron (N=81), Anoxypristis cuspidata (N=39), P. pristis (N=30), and P. pectinata (N=22). Sixteen specimens were labelled as Mediterranean: seven P. zijsron, five A. cuspidata, three P. pectinata, and one P. pristis. Since sawfish rostra have always been commonly traded among public and private collectors, we traced the geographic origin of 35 individual sawfish by characterizing the isotopic composition of oxygen (18O/16O) from the inorganic matrix (hydroxyapatite), and carbon (13C/12C) from the collagen of rostral teeth. We identified the most likely origin of the specimens and tested whether the Mediterranean labels were truly from the region. The geographical isoscape-based assignment associated most of the individuals precisely to one or two areas, including one P. zijsron assigned to the Mediterranean and 11 P. zijsron and P. pristis to the Red Sea/Persian Gulf. Using this integrated analytical approach, we retrieved novel information and data on sawfish past distribution contributing to increase the knowledge of their historical ecology.