Exploring syrphid fauna in Niella Tanaro: a forest with high species heterogeneity supported by surrounding ancestral agro-pastoral systems

In this study, we analyzed the hoverfly community (Diptera: Syrphidae) within the Niella Tanaro forest (southern Piedmont, Italy), a woodland area embedded in a traditional agro-silvo-pastoral landscape. This research represents the first comprehensive sampling of hoverflies in the area, with the aim of comparing species richness and functional diversity to that of two other relict oak forests (Merlino and Trino) surrounded by intensively farmed landscapes. Two complementary assessment tools were applied: Syrph the Net, which compares observed and expected species for given habitats, and the Index of Biodiversity Potential (IBP), which evaluates a forest’s capacity to support biodiversity. Niella Tanaro recorded high species richness (84 species) and the highest trophic and functional diversity among the three sites. The surrounding rural mosaic, rich in flowering plants and free from pesticide use, particularly favoured phytophagous, coprophagous, and commensal hoverflies, several of which are threatened at the European level. These results suggest the importance of semi-natural environments and traditional land-use practices in potentially supporting more heterogeneous and functionally complete insect communities, although broader studies are needed to confirm this pattern. Overall, the study confirms the high conservation value of traditional agro-ecosystems for preserving ecosystems services and functional diversity in hoverfly assemblages.