Landscape‐scale floral resource discontinuity decreases bumble bee occurrence and alters community composition

Abstract

Agricultural practices and intensification over the past two centuries have dramatically altered the abundance and temporal continuity of floral resources that support pollinating insects such as bumble bees. Long‐term trends among bumble bees within agricultural regions suggest that intensive agricultural conditions have created inhospitable conditions for some species, while other species have maintained their relative abundances despite landscape‐level changes in flower availability. Bumble bee responses to spatiotemporal resource heterogeneity have been explored at the colony and behavioral level, but we have yet to understand whether these conditions drive community structure and ultimately explain the diverging patterns in long‐term species trends. To explore the relationship between landscape‐level floral resource continuity and the likelihood of bumble bee occurrence, we mapped the relative spatial and temporal availability of floral resources within an intensive agricultural region in the US Upper Midwest and related this resource availability with bumble bee species relative abundance. Across the bee community, we found that relative bumble bee occurrence increases in landscapes containing more abundant and more temporally continuous floral resources. Declining species, such as Bombus terricola, exhibited the strongest, positive responses to resource abundance and continuity whereas common, stable species, such as B. impatiens, showed no statistical relationship to either. Together with existing experimental evidence, this work suggests that efforts to increase spatiotemporal flower availability, along with overall flower abundance at landscape scales may have positive effects on bumble bee communities in the US Upper Midwest.This article is protected by copyright. All rights reserved.

Homogenization of taxonomic, phylogenetic, and functional characteristics of bumble bee communities at regional scales in anthropogenic landscapes

“…Although the relationship between pollen load capacity and setae length on the corbicula warrants further study, the length of these setae was related to thorax width in B. terrestris (Goulson et al 2002) and hypothesized to allow smaller workers to carry greater pollen loads relative to their mass (Peat et al 2005b). This trait may be particularly beneficial in landscapes where floral resource availability is temporally inconsistent and/or spatially patchy such as urban and agricultural ecosystems (Hemberger et al 2023). While our results are consistent with others that have shown pollinator communities in urban ecosystems select for smaller species (Banaszak-Cibicka and Żmihorski 2012, Eggenberger et al 2019), other studies found the opposite pattern with larger species more likely to be found in urban areas (Merckx et al 2018, Fournier et al 2020, Theodorou et al 2021.…”