Variations in Nutritional Requirements Across Bee Species

Abstract

With 2,000 species currently recorded in Europe, bees are a highly diversified and efficient group of pollinating insects. They obtain their nutrients from nectar and pollen of flowers. However, the chemical composition of these resources, especially of pollen (e.g., protein, lipid, amino acids, fatty acids, or sterol content), is highly variable among plant species. While it is well-known that bees show interspecific variation in their floral choices, there is a lack of information on the nutritional requirements of different bee species. We therefore developed original experiments in laboratory conditions to evaluate the interspecific variations in bee nutritional requirements. We analyzed the chemical content of eight pollen blends, different in terms of protein, lipid, amino acids, and sterols total concentration and profiles. Each pollen blend was provided to four different bee model species: honey bees (Apis mellifera), bumblebees (Bombus terrestris), mason bees (Osmia bicornis and Osmia cornuta). For each species, specific protocols were used to monitor their development (e.g., weight, timing, survival) and resource collection. Overall, we found that the nutritional requirements across those species are different, and that a low-quality diet for one species is not necessarily low-quality for another one. While honey bees are negatively impacted by diets with a high protein content (~40%), bumblebees and mason bees develop normally on these diets but struggle on diets with a low total amino acid and sterol content, specifically with low concentrations of 24-methylenecholesterol and β-sitosterol. Overall, our study supports the need of conserving and/or introducing plant diversity into managed ecosystems to meet the natural nutritional preferences of bees at species and community level.

Natural processes influencing pollinator health

“…The challenge is that much more information is needed on the nutritional needs of specific pollinator taxa and the resources that provide them. Even for bees, most of the available information on nutritional ecology is for a limited number of species: Apis mellifera , Bombus and mason bees ( Osmia ) [ 64 ]. Traditional and new approaches to evaluating nutritional requirements are outlined here and by [ 65 ].…”

The impact of mass-flowering crops on bee pathogen dynamics

“…It is important to note that nutritional requirements differ between bee species. The definition of quality is therefore different depending on bee species ( Parreño et al, 2021 ; Barraud et al, 2022 ). For example, low amino acid and sterol content has been shown to negatively impact the development of bumble bees and mason bees, while honey bees were not impacted by these low contents ( Barraud et al, 2022 ).…”

“…The definition of quality is therefore different depending on bee species ( Parreño et al, 2021 ; Barraud et al, 2022 ). For example, low amino acid and sterol content has been shown to negatively impact the development of bumble bees and mason bees, while honey bees were not impacted by these low contents ( Barraud et al, 2022 ). Bumble bees re-assess pollen quality continuously to improve the colony health, as poor pollen diets decreased larval and pupal masses and increased larval ejection in bumble bees ( Ruedenauer et al, 2016 ; Roger et al, 2017 ).…”

“…Legume (Fabaceae) pollen, which includes many MFCs (see Table 1 ), is protein-rich ( Hanley et al, 2008 ). Yet, high protein content is not always beneficial for pollinators, as it was recently shown that pollen with a high protein content had a negative impact on honey bee survival ( Barraud et al, 2022 ). MFCs can have high nectar concentrations and are often more attractive (see Table 1 ) than existent flowers in field margins ( Esquivel et al, 2021 ), but they can become a sugar trap when pollen quality is inadequate, undermining the pollinators’ health.…”

“…In honey bees, polyfloral diets increased the glucose oxidase activity, which plays a role in social immunity by producing an antiseptic compound ( Alaux et al, 2010 ). Amino acids are likely the limiting factor here, since essential amino acids are needed in a certain amount and proportion for general bee health ( Alaux et al, 2010 ; Barraud et al, 2022 ). Arginine is an essential amino acid and a precursor of nitric oxide, which is thought to be a key effector molecule against diseases in invertebrates ( Negri et al, 2017 ).…”