New Insights About Distribution Areas of Telestes souffia and Telestes muticellus: Changes and Overlapping Zones for Community Interest Fish Species

Fish geographical distribution has pivotal importance in management/conservation policies, especially for community interest species, requiring careful protection measures. However, distribution areas could be difficult to define if the taxonomy has only recently been resolved, and particular attention must be paid where co-generic species share their ranges. Our work reports new insights about the distribution of T. muticellus and T. souffia in Northeastern Italy, where their geographical ranges overlap, and these native species share a cross-border area. Fish samplings and meristic and genetical investigations were performed, and our results showed that T. muticellus seems to expand its range east due to human-induced translocations, while T. souffia occurs only in the cross-border hydrological networks between Italy and Slovenia. Telestes genetic characterization for the Tagliamento River Basin and Northeastern Italy lowland is reported, improving the genus distribution dataset in the Po Plain watershed, where T. muticellus is endemic. The main meristic feature to discriminate the species was the number of lateral line scales, explaining 44.5% of the dissimilarity among the analyzed populations. Findings about the distribution of the investigated populations highlight the critical need for targeted conservation strategies in biodiversity hotspots, where overlapping species distributions, such as T. muticellus and T. souffia, play a vital role in preserving regional biodiversity.