Species traits elucidate crop pest response to landscape composition: a global analysis

Recent synthesis studies have shown inconsistent responses of crop pests to landscape composition, imposing a fundamental limit to our capacity to design sustainable crop protection strategies to reduce yield losses caused by insect pests. Using a global dataset composed of 5242 observations encompassing 48 agricultural pest species and 26 crop species, we tested the role of pest traits (exotic status, host breadth and habitat breadth) and environmental context (crop type, range in landscape gradient and climate) in modifying the pest response to increasing semi-natural habitats in the surrounding landscape. For natives, increasing semi-natural habitats decreased the abundance of pests that exploit only crop habitats or that are highly polyphagous. On the contrary, populations of exotic pests increased with an increasing cover of semi-natural habitats. These effects might be related to changes in host plants and other resources across the landscapes and/or to modified top-down control by natural enemies. The range of the landscape gradient explored and climate did not affect pests, while crop type modified the response of pests to landscape composition. Although species traits and environmental context helped in explaining some of the variability in pest response to landscape composition, the observed large interspecific differences suggest that a portfolio of strategies must be considered and implemented for the effective control of rapidly changing communities of crop pests in agroecosystems.

Honey bee pollen foraging ecology across an urbanization gradient

Understanding animal foraging ecology requires large samples sizes spanning broad environmental and temporal gradients. For pollinators, this has been hampered by the laborious nature of morphologically identifying pollen. Metagenetic pollen analysis is a solution to this issue, but the field has struggled with poor quantitative performance. Building upon prior laboratory and bioinformatic methods, we applied quantitative multi-locus metabarcoding to characterize the foraging ecology of honey bee colonies situated along an urban-agricultural gradient in central Ohio, USA. In cross-validating a subset of our metabarcoding results using microscopic palynology, we find strong concordance between the molecular and microscopic methods. Our results show that, relative to the agricultural environment, urban and suburban environments were associated with higher taxonomic diversity and temporal turnover of honey bee pollen forage. This is likely reflective of the fine-grain heterogeneity and high beta diversity of urban floral landscapes at the scale of honey bee foraging. Our work also demonstrates the power of honey bees as environmental samplers of floral community composition at large spatial scales, aiding in the distinction of taxa characteristically associated with urban or agricultural land use from those distributed ubiquitously across our landscape gradient.