The positive association between natural vegetation, native coccinellids and functional diversity of aphidophagous coccinellid communities in alfalfa

Abstract

1. A greater taxonomic and functional diversity of natural enemies in agroecosystems is frequently positively associated with more effective pest control, due to the complementarity of species or traits. But this diversity has declined with landscape homogenisation and loss of natural covers, particularly losing native species, which play an important role in pest suppression within crops. 2. We evaluated the effect of landscape on coccinellid communities and aphids, and the relative contribution of coccinellids and aphids in shaping taxonomic and functional diversity of coccinellid communities in alfalfa fields. 3. We characterised the landscape at 1 kmradius surrounding 17 alfalfa fields, and the taxonomic and functional diversity of coccinellid communities collected throughout the season in alfalfa. Functional diversity indices considered four traits: body size, habitat specialisation, ubiquity and temporal variability. 4. We found a positive association among native coccinellids in alfalfa and the amount of natural cover in the landscape, while aphids positively associated with agricultural cover. Also, we found a positive association among functional and taxonomic diversity indices with native coccinellids, and a negative association with exotics, demonstrating the contribution of native coccinellids in adding taxonomic and functional diversity to the aphidophagous communities in alfalfa fields. Aphids also associated positively with some functional and taxonomic diversity indices. 5. Our results highlight the need to promote appropriate management practices in agricultural landscapes in order to conserve native coccinellid species in alfalfa, maintain a diversified species pool and their potential for aphid pest suppression.