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

Abstract

The role plant diversity has played in regulating insect communities has been of interest for decades. 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 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 provide economic opportunities for farmers must be developed in order to promote sustainable and resilient ecosystems. Here we tested the capacity of an alternative cropping system to support more diverse insect populations than conventional cropping systems. We quantified differences in the diversity of an insect taxon, ants (Hymenoptera: Formicidae), over an annual cycle using pitfall traps in thirty-two 2-m2 plots of either woody perennial polycultures that contained apples, chestnuts, currants, hazelnuts, and raspberries or conventional corn-soybean rotations. In doing so, we found that woody perennial polycultures supported 2.4-fold more ant species and maintained a unique fauna of specialist and predatory ants. The observed differences in diversity were linked to higher levels of predation as 18.2-fold more sentinel prey were consumed 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.