Extending the ‘resource concentration hypothesis’ to the landscape-scale by considering dispersal mortality and fitness costs

The ‘resource concentration hypothesis’ proposes mechanisms by which polycultures (local plant diversity) can directly reduce densities of insect pests in agriculture. It predicts that herbivore loads are directly reduced because host plant cues are disrupted and herbivore residency times are shorter in polycultures than in monocultures. The hypothesis has been similarly applied to landscape-scale investigations; however, the mechanisms by which diverse landscapes can directly suppress herbivores are likely different than those operating at the polyculture scale and have not been clearly articulated. Here, we discuss how landscape-scale habitat diversity may directly reduce agricultural pest loads by requiring more dispersal activity, which, in turn, can increase mortality and decrease fitness. We also lay out a research agenda and argue that a better understanding of the mechanisms by which landscape-scale habitat diversity affect insect pest populations can lead to better predictions of pest control as an ecosystem service provided by diverse agricultural landscapes.