Sharing enemies: evidence of forest contribution to natural enemy communities in crops, at different spatial scales

Abstract

The increase in cultivated lands has led to ecosystem and biodiversityloss. Arthropod natural enemies, involved in the ecosystem service of biologicalcontrol, benefit from non-crop habitat and may be affected by itsproximity and amount in the landscape.2. We have evaluated natural enemy richness and composition in relation toforest cover in the landscape and distance from the forest, for a Chaco Serranoforest-soybean crop system. Forest contribution to natural enemies on soybeanwas also investigated, by assessing similarities between forest and crop assemblages,and examining body size of shared enemies in relation to distance fromthe forest. In nine landscape circles, yellow pan traps were placed in forest and soybean crops (5, 25, 50 and 100 m from forest edge), which collected 8041specimens representing 290 species.3. Species richness of natural enemies was positively related to forest coverand declined from the forest to the furthermost soybean locations, with bothforest cover and its proximity affecting community composition. Also, similarityof forest and crop assemblages increased with forest cover and proximity.Finally, forest-crop shared assemblages showed larger average body size atgreater distances from the forest, indicating dispersal limitations on forest contribution to the crop.4. Our results suggest that forest species are important components of naturalenemy communities on soybean, and that both the amount of natural habitatand its proximity may influence agroecosystems. We emphasise the importanceof non-crop habitat to help maintain natural enemy communities and ensurethe ecosystem service of pest control.