How much do rare and crop-pollinating bees overlap in identity and flower preferences?
Abstract
The biodiversity-centred approach to conservation prioritizes rare species, whereas the ecosystem services approach prioritizes species that provide services to people. The two approaches align when rare species provide ecosystem services, or when both groups of species benefit from the same management action. We use data on bee pollinators and the plant species they forage on to determine if there are rare species among the most important crop pollinators, and the extent to which plant species selected to support crop pollinators would support rare species as well. We used pre-existing, regional-scale datasets to determine which bee species are regionally rare, and which are regionally important crop pollinators. To assess the plant preferences of these two groups of bee species, we collected two datasets on plant-pollinator interactions, one experimental and one observational. The experiment consisted of monospecific plots of 17 plant species from which we collected bees over 3 years. The observational data consisted of bees collected from 66 species of plants growing in semi-natural meadows, also over 3 years. Nineteen percent of the dominant crop-pollinating species were regionally rare. Both rare species and crop-pollinating species had strong preferences for certain plants, and the preferences of rare and crop-pollinating bees were significantly but not strongly (r ≤.54) correlated. Ten plant species were significantly preferred by both rare and crop-pollinating bees. Synthesis and applications. We found several dominant crop pollinators that are rare at a regional scale, supporting the idea that rare species can be important providers of ecosystem services. The flower preferences of rare and crop-pollinating bees are significantly positively associated, suggesting that plants chosen to support crop pollinators will benefit rare species as well. We identify plant species that are preferred by regionally rare bees and by crop pollinators, including 10 plant species preferred by both types of bees, and recommend these for use in pollinator habitat plantings.