Thesis (Ph.D.) - Indiana University, Biology, 2015Perennializing grain cropping systems has been proposed as a way to mitigate the challenges facing agriculture in the future due to crop intensification. Crop intensification is characterized by utilizing more land and inputs, less crop diversity, and greater crop density. Perennial cropping systems use native prairie as a model and model diverse prairie communities with perenniality and polyculture. Perennial cropping systems allow for complex planting arrangements (e.g. crop frequency, intercrops, and row spacings) that could confer specialist insect pest resistance via reduced host plant apparency, changes in herbivore attraction, and host plant tissue quality. The three chapters in this dissertation examine these themes of perennial polyculture and effects of spatial heterogeneity on insect abundance. The first chapter compares insect herbivore, predator and parasitoid, pollinator, and detritivore abundance, morphospecies richness, and biovolume among hayed grasslands, and wheat fields. Pollinators and detritivores were more abundant, had greater biovolume, and were more species-rich in hayed grasslands than in wheat fields. Therefore, insects may provide more pollination and decomposition ecosystem services in hayed grasslands. However, grasslands and wheat fields supported comparable numbers of herbivores, suggesting that herbivore densities in grasslands are not any more limited by predators and parasitoids than herbivore densities in wheat fields. The second chapter examined insect herbivore foliar feeding on a legume, Desmanthus illinoensis, which is in the early stages of development as a perennial grain crop. Insect herbivory was examined in the context of prairies. Local neighborhood grass cover strongly influenced insect herbivore foliar feeding; greater grass cover within the plant neighborhood resulted in lesser foliar herbivory. Our results suggest that incorporation of crop diversity, through the addition of a grass, in perennial agroecosystems with D. illinoensis could result in reduced foliar feeding by a specialist herbivore. The third chapter examined a legume (D. illinoensis)-grass (Thinopyrum intermedium) intercrop with row spacing and initial frequency of legume seed treatments. The bicultures were productive which suggests that incorporating crop diversity could benefit perennial polyculture. However, row spacing and seeding frequency had little effect on plant herbivory in this agroecosystem, most likely due to dominance of generalist herbivores.