Identity of mass-flowering crops moderates functional trait composition of pollinator communities

Abstract

Context Pollinator declines and functional homogenization of farmland insect communities have been reported. Mass-flowering crops (MFC) can support pollinators by providing floral resources. Knowledge about how MFC with dissimilar flower morphology affect functional groups and functional trait compositions of wild bee communities is scarce. Objective We investigated how two morphologically different MFC, land cover and local flower cover of semi-natural habitats (SNH) and landscape diversity affect wild bees and their functional traits (body size, tongue length, sociality, foraging preferences). Methods We conducted landscape-level wild bee surveys in SNH of 30 paired study landscapes covering an oilseed rape (OSR) (Brassica napus L.) gradient. In 15 study landscapes faba beans (Vicia faba L.) were grown, paired with respective control landscapes without grain legumes. Results Faba bean cultivation promoted bumblebees (Bombus spp. Latreille), whereas non-Bombus densities were only driven by the local flower cover of SNH. High landscape diversity enhanced wild bee species richness. Faba bean cultivation enhanced the proportions of social wild bees, bees foraging on Fabaceae and slightly of long-tongued bumblebees. Solitary bee proportions increased with high covers of OSR. High local SNH flower covers mitigated changes of mean bee sizes caused by faba bean cultivation. Conclusions Our results show that MFC support specific functional bee groups adapted to their flower morphology and can alter pollinators` functional trait composition. We conclude that management practices need to target the cultivation of functionally diverse crops, combined with high local flower covers of diverse SNH to create heterogeneous landscapes, which sustain diverse pollinator communities.

The contrasting response of cavity‐nesting bees, wasps and their natural enemies to biodiversity conservation measures

“…The posterior probability of each model was assessed via BIC model weights ( w i ) (Link & Barker, 2006). In order to assess the relative importance of each predictor variable, we calculated BIC model weights (∑ w i ) over all models that include the respective explanatory variable (as in the study by Beyer et al, 2021).…”

Irish faba beans (Fabales: Fabaceae) depend on wild bumblebee pollination for marketable yields

“…An increase of faba bean cultivation in the landscape can enhance bumblebee populations, particularly long-tongued bumblebee species (Beyer et al, 2021). Faba beans may be particularly important in terms of colony initiation for long-tongued bumblebees because its blooming time coincides with the emergence of queens and subsequent workers from many long-tongued bumblebee species, as opposed to earlier emerging short-tongued species (Goulson et al, 2005).…”

Functional diversity of farmland bees across rural–urban landscapes in a tropical megacity

“…They can therefore benefit from urbanization provided enough floral resources are supplemented (Fortel et al, 2014). Indeed, Hamblin et al (2018) demonstrated that abundant floral resources promoted large bees (more than small bees) in dense urban environments as they can fly longer distances in fragmented landscapes and concentrate in highly rewarding flowering patches, such as mass‐flowering crops (e.g., lablab) (Beyer et al, 2021; Zaninotto et al, 2021).…”

“…Such complex landscapes provide complementary food resources across the seasons (Grass et al, 2021; Martins et al, 2018; Sutter et al, 2017). Wild flower strips, field margins, or other seminatural habitats, such as hedges, increase flower resources and nesting sites, which further promote bee communities at the local and landscape scales (Beyer et al, 2021; Ganser et al, 2021). The same measures could likely mitigate the potential negative effects of urbanization, thereby enhancing vital pollination services for urban farmers.…”