Response diversity, but not cross-scale resilience, stabilizes blueberry pollination in response to agricultural land use

Substantial evidence suggests that biodiversity can stabilize ecosystem function, but how it does this is less clear. The leading hypothesis is that biodiversity stabilizes function through compensatory dynamics, which occur when at least two species in a community show different responses to environmental conditions. Here, we focus on two forms of compensatory dynamics, namely cross-scale resilience (CSR) and response diversity (RD). CSR occurs when species contributing to the same function respond to a given type of disturbance at different scales, such that scale-specific disturbances do not negatively affect all species. RD occurs when species contributing to the same ecosystem function show different responses to an environmental change. We studied bee pollination of blueberry at 16 farms that varied in the amount of surrounding agricultural land use, and developed a new analytical approach to compare the strength of CSR and RD in the same dataset. We then asked whether CSR and RD among native bee species are associated with the stability of blueberry pollination. Although CSR and RD were both present, only RD was associated with higher stability of pollination. The effects of RD on stability were overwhelmingly due to a dominant blueberry specialist (Andrena bradleyi) that increased in abundance in response to agricultural land use, which is primarily blueberry fields. Our results from a real-world agricultural system contrast with results of the biodiversity-ecosystem functioning field generally, which predicts that compensatory dynamics - and thus the stabilization of ecosystem function - will increase with the number of species present.