Functional role of different habitat types at local and landscape scales for aphids and their natural enemies

The functional roles of different habitats may depend on the combined effect of local habitat management and the structure and composition of the surrounding landscape. However, this interaction is not well understood due to the common practice of pooling many different habitat types in one simple landscape metric (e.g., percentage crop area). In this study, we investigate the interactive effects of local and landscape factors on the abundance and species richness of aphids and their natural enemies, as well as primary parasitism and hyperparasitism rates. We selected 41 fields in Central Serbia with three disturbance levels at the local scale (wheat fields, alfalfa fields, and fallows) embedded in 15 landscapes that varied in percentage of annual crops, grasslands, and shrublands. We found ecosystem disservices to be promoted in wheat fields, where both aphid abundances and hyperparasitism rates were approximately threefold higher than in alfalfa fields and fallows. Concurrently, alfalfa fields supported at least twofold higher primary parasitism rates and predator (coccinellid) abundances than either wheat fields or fallows. The proportion of grasslands in the surrounding landscape had no effect on any organism group while shrublands appear to be important for both polyphagus predators and pests in some crops, a pattern not revealed when all semi-natural habitats in the landscape are pooled together. Our results imply that the roles of different habitat types at both local and landscape scales should be considered in a multifunctional agricultural management approach, which if adopted may provide better ecosystem services for multiple agroecosystem types.