Influence of habitat and landscape perenniality on insect natural enemies in three candidate biofuel crops

Abstract: Cultivation of biofuel crops could change agricultural landscapes, affecting natural enemies at multiple scales. We sampled five natural enemy families with sticky cards in three model biofuel habitats (corn, switchgrass and prairie; n =60) across southern Michigan and Wisconsin, comparing captures between habitats and relating them to the area of forest, annual crop and herbaceous perennial habitat in the landscape within 2km of sites. In a first analysis, we compared Coccinellidae assemblages between habitats and examined the impact of habitat type and landscape composition on species richness and abundance. Results showed that, at the habitat scale, perennial grasslands supported a greater abundance of uncommon, native coccinellids and hosted distinct species assemblages compared to corn. At a broader scale, abundances of exotic and uncommon native ladybeetles responded differently to landscape composition, decreasing with the area of herbaceous perennials and annual crops, respectively. In a second analysis, we related family-level abundances of Anthocoridae, Syrphidae, Dolichopodidae and Chrysopidae to habitat type and landscape composition. Dolichopodids were more abundant in grasslands, while anthocorid and syrphid abundance increased over fivefold with the area of herbaceous, perennial habitat in the landscape surrounding corn, but not grassland, sites. These findings suggest that perennial grasslands used for bioenergy production could conserve natural enemies which are less abundant in corn, the dominant biofuel in existing landscapes. Moreover, cultivating annual cropland with herbaceous, perennial habitats could affect the abundance of natural enemies in existing crops and alter the suitability of entire landscapes for these beneficial taxa. [Copyright &y& Elsevier]