Grassland strip width of transhumance drove roads as a key factor of ant biodiversity in agrarian landscapes of central Spain

Abstract Ongoing intensification and fragmentation of European agricultural landscapes have accelerated biodiversity loss and disrupted essential ecological functions. In the Mediterranean region, drove roads, traditionally used for livestock movement, serve a critical ecological role by supporting connectivity and acting as reservoirs for local biodiversity. However, their effectiveness as biodiversity reservoirs is closely linked to the width of their grassland habitats, which are increasingly threatened by land-use changes, such as the abandonment of transhumance, habitat degradation, and invasion by neighbouring croplands. This study evaluated the effect of natural habitat availably, measured as grassland strip width and dirt road width, and surrounding landscape composition on the capacity of drove roads to support ant taxonomic and functional diversity in intensively farmed landscapes in central Spain. We characterized ant assemblages across 20 drove road sections based on taxonomic diversity (species richness and diversity, species composition, and nestedness pattern) and functional diversity (FD). Our results reveal that grassland strip width, rather than landscape composition, is the main factor influencing the role of drove roads as local reservoirs of ant taxonomic and functional diversity. Wider grassland strips supported species-rich and diverse communities and a broader range of functional traits compared to narrower corridors, which only contained a subset of species, predominantly generalists. This study underscores the importance of preserving the natural width of drove roads to maintain biodiversity and ecological functions, particularly in intensively managed agricultural landscapes.