Floral resources predict the local bee community: Implications for conservation

Flowering plants provide critical resources for wild bees. Consequently, enhancing flowering plant communities through hedgerows or flower strips has become a common recommendation to support native pollinator populations. Meta-analysis finds that enhancements are associated with higher local bee diversity. However, many studies have also examined the impacts of unmanipulated (i.e., existing, naturally occurring) plant communities on the local bee community. These studies have typically been excluded from meta-analysis, leaving a partial picture of how local plant communities influence bees. We compiled studies of either approach that looked for an association between bee abundance and/or diversity and local floral resources, measured as floral abundance and/or diversity. From literature surveys, we discovered 60 relevant studies, from which we extracted 133 different effect sizes. Then, using meta-regression, we examined four relationships between floral community traits (i.e., floral abundance and diversity) and bee community traits (i.e., abundance and diversity). Overall, we found strong associations between the plant community and the bee community, regardless of study design, or ecosystem type. To ensure the support of abundant and diverse wild bee populations, our results indicate plant enhancements should be designed to optimize both floral diversity and abundance.