Woody perennial polycultures increase ant diversity and ant-mediated ecosystem services compared to conventional corn-soybean rotations

Authors: Roeder, Karl; HARMON-THREATT, ALEXANDRA - University Of Illinois

Submitted to: Agriculture, Ecosystems and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2022
Publication Date: 5/26/2022
Citation: Roeder, K.A., Harmon-Threatt, A.N. 2022. Woody perennial polycultures increase ant diversity and ant-mediated ecosystem services compared to conventional corn-soybean rotations. Agriculture, Ecosystems and Environment. https://doi.org/10.1016/j.agee.2022.108025.
DOI: https://doi.org/10.1016/j.agee.2022.108025

Interpretive Summary: Plant diversity plays an important role in regulating the diversity of insects. However, the agricultural landscape of the midwestern United States has become more simplified over the past 100 years with large portions of land primarily dominated by only two species—corn and soybean. In this paper, we test how increasing plant diversity (i.e. moving from a monoculture to a polyculture) impacts one beneficial arthropod group, the ants, over an annual cycle. In doing so, we found that polycultures harbor more ant species (17 species) compared to conventional monocultures (7 species) and that increase in diversity was correlated with significantly higher attack rates and consumption of sentinel prey. Our data provide strong evidence that landscapes in the midwestern United States can be modified to support important beneficial insects like ants while still producing commodities that can be economically beneficial to farmers.

Technical Abstract: The role plant diversity has played in regulating insect communities has been of interest for decades with recent syntheses from agroecosystems suggest increasing plant diversity can positively affect beneficial insects like predators, reducing pest pressure and increasing yield. However, the agricultural landscape of the midwestern United States is primarily dominated by just two crops—corn and soybean—which cover approximately 180 million acres of arable land yearly. New ideas to conserve wildlife that additionally provides economic opportunities for farmers must be developed and tested in order to promote sustainable and resilient ecosystems. Here we test one such idea by quantify differences in the diversity of an insect taxon, ants (Hymenoptera: Formicidae), in woody perennial polycultures and conventional corn-soy rotations over an annual cycle. In doing so, we found that woody perennial polycultures not only support 2.4-fold more ant species, but they also maintained a unique fauna of specialist and predatory ants that were not found in conventional corn-soy rotations. The observed differences in diversity were linked to higher levels of predation as ants in polycultures attacked and consumed 18.2-fold more sentinel prey during each month of the growing season. Combined, our results suggest that agricultural landscapes in the midwestern United States can be modified to support important beneficial insects like ants while still producing commodities that can be economically beneficial to farmers.