Genetic structure assessment of the freshwater Etruscan Goby Padogobius nigricans (Canestrini, 1867) and eDNA-based monitoring approach

The Etruscan freshwater goby Padogobius nigricans (Canestrini, 1867) is a small freshwater fish, endemic to Central Italy. It is presently listed as Endangered in the Italian IUCN Red List because of recently increasing local extinctions and overall population declines. Nevertheless, there is no available information on spatial patterns of genetic diversity, despite its pivotal contribution to threatened taxa conservation. We therefore analyzed mitochondrial sequences to (a) assess genetic structure and spatial diversity of populations sampled in different basins; (b) investigate the existence of potentially distinct genetic lineages; and (c) test whether isolation between basins and genetic drift could explain the expectedly high intraspecific differentiation in P. nigricans, as emerged in other poor vagile Italian freshwater fish species. Here we report preliminary results on populations from three major basins: Magra-Vara, Arno and Tiber. In addition, because of the cryptic nature of P. nigricans, we tested non-invasive monitoring (presence/absence) through environmental DNA (eDNA) barcoding from water samples in different sites from Latium. The effectiveness of such a method is validated by comparisons with traditional-invasive surveys based on electrofishing. The development of a suitable eDNA-specific bio-monitoring protocol, together with data obtained from genetic analysis, could improve future efforts for conservation actions targeted at endangered and elusive species such as P. nigricans.