Abstract
Agricultural intensification, particularly pesticide use, has reduced beneficial organisms and their functional diversity in agroecosystems. We studied the effects of pulsed exposure to two common insecticides, Mospilan 20 SP (neonicotinoid - active ingredient (a.i.) acetamiprid) and Sherpa 100 EC (pyrethroid - a.i. cypermethrin), on the non-target ground beetle Poecilus cupreus (Coleoptera: Carabidae) in a large-scale landscape context. Laboratory bred beetles (F2) from two agricultural landscapes of varying complexity (low vs. high) and two habitat types with differing pesticide pressure (crops vs. meadows) were tested. We hypothesized that beetles from high agricultural pressure habitats would exhibit reduced susceptibility to insecticides due to adaptations from repeated exposures, with stronger effects in low-complexity landscapes. Insecticide response depended on landscape complexity and habitat type. Beetles from high-pressure habitats showed reduced sensitivity in low-complexity landscapes. Mortality was higher in low-pressure habitats within low-complexity landscapes. Sherpa exposure caused sublethal effects on acetylcholinesterase (AChE) activity, influenced by prior insecticide exposure. Control beetles from high-pressure habitats exhibited higher initial AChE activity than those from low-pressure habitats. Sherpa exposure increased AChE activity in beetles from low-pressure habitats but decreased it in those from high-pressure habitats. Our findings emphasize that insecticide effects are context-dependent, influenced by landscape complexity, habitat type, and prior exposure. They underscore the importance of considering long-term, multi-generational perspectives in ecotoxicological studies and augmentative pest management.