Fly high for conservation: assessing area-based conservation in a temperate Mediterranean forest through parasitoid fly communities

Area-based conservation—relying on the strategic designation and zoning of protected areas—remains one of the most effective approaches to counter global biodiversity loss. This strategy facilitates the integration of conservation objectives with sustainable development, ensuring that ecological and social needs are balanced. This is particularly important in ecosystems highly sensitive to global change, such as Mediterranean mountain forests, which often harbor ecological communities typical of temperate regions yet are subject to prolonged summer drought and warmer conditions. The Gariglione forest, located within the Sila National Park (Southern Italy), exemplifies this scenario. Historically managed until the mid-20th century, Gariglione has since undergone substantial rewilding thanks to its designation as a reserve, regaining key features of old-growth structure—such as tall canopies and abundant late-successional species like Abies alba and Fagus sylvatica. Furthermore, its location within a buffer zone where only activities compatible with conservation objectives are permitted makes Gariglione an ideal testing ground to evaluate conservation strategies that extend beyond the traditional assumption that stricter protection always yields higher biodiversity. Indeed, growing evidence suggests that intermediate-disturbance mosaics—where low-intensity human uses coexist with conservation objectives—can enhance ecological complexity while supporting local livelihoods. Building on this foundation, this work aims to assess the effectiveness of zoning and to investigate the factors contributing to biodiversity patterns in these dynamic ecosystems. In this regard, insects represent the ideal target for monitoring changes in ecosystem health. With their short generation times and high sensitivity to microenvironmental changes, insects serve as early-warning indicators, capable of revealing subtle shifts in forest structure, microclimate, and resource dynamics long before these changes become apparent in vegetation or larger fauna. Bristle flies (Diptera: Tachinidae) exhibit high functional and taxonomic diversity yet are rarely studied in the context of forest conservation in southern Europe. By monitoring these parasitoid flies, we can assess their diversity and indirectly infer the health and composition of their host communities—critical for processes such as pest regulation and nutrient cycling. Comparing communities of Tachinidae across an integral reserve gradient of structural complexity and managed areas where moderate human activities are allowed, we present preliminary results that explore the potential of these parasitoids to signal changes in forest integrity. We integrate classical diversity metrics and compositional analyses with forest structural indices and functional trait data to reveal the ecological mechanisms driving the observed community patterns. Ongoing analyses suggest that areas with intermediate disturbance can create a mosaic of microhabitats—through the formation of canopy gaps, varied light conditions, and a dynamic understory—that enhances habitat heterogeneity and supports higher parasitoid diversity. In strictly protected, old-growth conditions—where the natural decay of senescent trees, accumulation of deadwood, and formation of canopy openings generate diverse microhabitats—the forest also supports rich assemblages of host and parasitoid species. However, in some strictly protected areas, the forest may have experienced less recent structural heterogeneity, potentially resulting in a somewhat reduced niche diversity for insects.