Bees and butterflies respond differently to fire and grazing management in remnant tallgrass prairie

Butterflies and bees are essential components of grassland ecosystems; they contribute significantly to biodiversity and play important roles as pollinators and herbivores. With these insects tied so intrinsically to their plant communities, grassland conservation and management must be seen through the lens of insect conservation and management. Grasslands are a product of climate and natural disturbances such as fire and grazing. In North America, these natural disturbances have changed considerably since European settlement. Understanding the impacts of current fire and grazing regimes on butterfly and bee communities will allow land managers and conservationists to better protect and manage remnant prairie. We examined butterfly and bee responses to fire vs. grazing in Minnesota tallgrass prairie. Twenty remnant prairies (10 burned, 10 grazed) in Minnesota with known management histories were surveyed for butterflies, bees, vegetation, and surrounding land-use in 2016 and 2017. Bees and butterflies responded differently to fire vs grazing management in our study. Both fire and grazing managements supported unique species of bees and butterflies. Butterfly abundance, but not richness, was higher in burned than grazed prairies, and prairie-associated grass-feeding butterflies were more abundant at sites with higher plant species richness. Bee abundance was higher at sites with sandier soils and bee species richness was positively associated with forb frequency. Butterfly and bee abundance at burned and grazed tallgrass prairies within our study were significantly negatively correlated. These findings point to the importance of a mosaic of management practices across the prairie landscape.