(2nd Place) Bison and bees: A forgotten relationship tied together by disturbance

Plains bison (Bison bison) evolved with and played major roles in shaping and maintaining the biodiversity of North American grasslands. Many relationships among grassland organisms were lost following the extermination of bison herds from the continent. Now, with reintroduction efforts, threads of these former relationships are reappearing on the landscape. Our research follows one of these threads back to the nest entrances of bees and wasps found in the bison wallows of Nachusa Grasslands’ tall-grass prairies (TGP). Bison wallows are spaces of bare ground, devoid of vegetation, created by the wallowing (rolling) of these megafauna; bare ground is an important microhabitat for ground-nesting bees and wasps. Our research investigates how the biotic disturbance of wallowing affects ground-nesting bee and wasp communities by changing the physical environment. We compare wallows to the surrounding TGP habitat using metrics related to nest site selection and success (soil bulk density, soil texture, soil temperature). We found greater diversity and abundance of ground-nesting bees and wasps inside wallows than in the surrounding TGP. Wallow size, aspect, soil bulk density, and soil temperature were all strong drivers of nesting bee and wasp community composition. In conclusion, we document a novel indirect interaction with important implications for both grassland management and pollinator conservation. The bees and wasps of North American grasslands have coexisted and evolved with dynamic disturbances created by the behavior of large mammal herds; therefore, it is crucial to understand how bee and wasp communities respond to the reintroduction of these historic disturbance regimes.