Spiders of Val Grande National Park (NW Italy) (Arachnida: Araneae): faunistic contributions and ecological insights from a protected area

We provide an inventory of the spiders (Arachnida: Araneae) inhabiting the Val Grande National Park (NW - Italy) based on literature data, reliable iNaturalist observations and an original survey conducted between 2018 and 2019 in the frame of the “Biodiversity Monitoring Project” (BMP). In total, we report 157 species belonging to 92 genera and 25 families, including 11 new records for Piemonte and 103 new records for the Province of Verbano-Cusio-Ossola. Linyphiidae and Gnaphosidae were the most represented families, consistently with other protected areas across the Alps. Most species exhibited a Palearctic or European distribution, with a small proportion of endemics. Based on the original data gathered with standardized transects of pitfall traps we analysed species richness and abundance along the altitudinal gradient, revealing a general increasing trend with elevation. We also analyse the relationship between species composition and environmental variables using Canonical Correspondence Analysis (CCA) and revealed that species composition was significantly influenced by elevation and habitat type, highlighting clear ecological structuring along the altitudinal gradient. Beyond the faunistic contribution, we highlight the importance of faunal inventories for biodiversity conservation, particularly for lesser-known taxa like spiders, whose protection depends on accurate occurrence data within protected areas.