Unravelling the dependence of a wild bee on floral diversity and composition using a feeding experiment

Zuzanna M Filipiak,Bożena Denisow,Ernest Stawiarz,Michał Filipiak

doi:10.1016/j.scitotenv.2022.153326

Zuzanna M Filipiak, Bożena Denisow + Show 2 more

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https://doi.org/10.1016/j.scitotenv.2022.153326

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Abstract

We investigated nutrition as a potential mechanism underlying the link between floral diversity/composition and wild bee performance. The health, resilience, and fitness of bees may be limited by a lack of nutritionally balanced larval food (pollen), influencing the entire population, even if adults are not limited nutritionally by the availability and quality of their food (mainly nectar). We hypothesized that the nutritional quality of bee larval food is indirectly connected to the species diversity of pollen provisions and is directly driven by the pollen species composition. Therefore, the accessibility of specific, nutritionally desirable key plant species for larvae might promote bee populations. Using a fully controlled feeding experiment, we simulated different pollen resources that could be available to bees in various environments, reflecting potential changes in floral species diversity and composition that could be caused by landscape changes. Suboptimal concentrations of certain nutrients in pollen produced by specific plant species resulted in reduced bee fitness. The negative effects were alleviated when scarce nutrients were added to these pollen diets. The scarcity of specific nutrients was associated with certain plant species but not with plant diversity. Thus, one of the mechanisms underlying the decreased fitness of wild bees in homogenous landscapes may be nutritional imbalance, i.e., the scarcity of specific nutrients associated with the presence of certain plant species and not with species diversity in pollen provisions eaten by larvae. Accordingly, we provide a conceptual representation of how the floral species composition and diversity can impact bee populations by affecting fitness-related life history traits. Additionally, we suggest that mixes of ‘bee-friendly’ plants used to improve the nutritional base for wild bees should be composed considering the local flora to supplement bees with vital nutrients that are scarce in the considered environment.

Highlights

Much is understood about the details of the functioning of wild bees, knowledge of connections among the various elements of wild bee nutrition and well-being that would allow a broad, ecosystemoriented understanding of wild bee ecology and conservation is still lacking (Leonhardt et al, 2020; Parreño et al, 2021; Van der Kooi et al, 2021)
The pollen pools used in the feeding experiment differed in nutritional quality, as reflected by the proportions of the studied elements (Fig. 2)
The Control-Osmia, Apis1 and Apis2 pollens had similar nutritional quality; -CuZn1 and -CuZn2 were scarce in Cu and Zn, -KP was scarce in K and P, and -NaP was scarce in Na and P (Fig. 2)

Summary

Introduction

Much is understood about the details of the functioning of wild bees, knowledge of connections among the various elements of wild bee nutrition and well-being that would allow a broad, ecosystemoriented understanding of wild bee ecology and conservation is still lacking (Leonhardt et al, 2020; Parreño et al, 2021; Van der Kooi et al, 2021). The term ‘deficiency in food resources’ means that less food is available and refers to the decreased nutritional quality of food sources available in inhabited ecosystems Such changes result in mismatches between what wild bees need and what is offered by their environment, contributing to bee decline (Hemberger et al, 2021; Parreño et al, 2021; Trinkl et al, 2020; Vaudo et al, 2015; Wilson et al, 2021). We hypothesize that this mechanism is based on the differences between bee nutritional demands and environmental nutritional supplies: (1) wild bees may be often unable to achieve a nutritional balance in their diets because only a strictly limited number of plant species provide the required resources in the needed proportions (Filipiak, 2019; Parreño et al, 2021; Van der Kooi et al, 2021; Zu et al, 2021), and (2) these plants may be not available in certain landscapes with specific floral compositions, which negatively affects bees (Filipiak, 2019; Hemberger et al, 2021; Jachuła et al, 2017; Parreño et al, 2021; Stein et al, 2020; Wilson et al, 2021; Zajdel et al, 2019)

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