- A new study analyzed pollen from 57 North American plant species, identifying which ones are most nutritionally beneficial to bees, which could inform conservation efforts and wildflower restoration projects.
- Based on their findings, the researchers recommend emphasizing roses (Rosa sp.), clovers (Trifolium sp.), red raspberries (Rubus idaeus), buttercups (Ranunculus acris), and Tara vine (Actinidia arguta) in wildflower restoration projects, citing their ideal protein-to-lipid ratios in pollen for wild bee nutrition.
- Research has shown that bees need a diverse diet from multiple plant sources to obtain a balanced intake of essential fatty acids and amino acids, as no single plant species provides optimal nutrition.
- With many bee species facing significant threats, the researchers hope these findings can inform conservation efforts, from policy changes to individual actions such as planting native flowers and reducing pesticide use.
What’s on a healthy bee’s menu? A team of researchers delved into the world of bee nutrition, analyzing pollen to identify the best food sources for these essential pollinators. Their findings could have implications for bee conservation efforts and pollinator-friendly landscaping.
The research, published in The Frontiers of Sustainable Food Systemsanalyzed the nutritional content of pollen collected from 57 species of plants native to North America. The research team, led by Sandra Rehan of York University in Canada, looked at levels of essential fatty acids, amino acids and other key nutrients in the pollen samples.
“Despite public interest and increased pollinator planting, little is known about which plant species are best suited for bee health,” Rehan said. “This study aimed to better understand the nutritional value of plant species.”
Based on their findings, the researchers recommend focusing on roses (Pink sp.), clovers (Trifolium sp.), red raspberry (Rubus idaeus), large buttercup (Buttercup acris), and the vine of Tara (Actinidia arguta) in wildflower restoration projects, citing their ideal protein-to-lipid ratios in pollen for wild bee nutrition.
They found this big buttercup (Buttercup acris) was best suited to the bees’ dietary needs, followed closely by the hardy kiwi (Actinidia arguta), bird’s foot trefoil (Horned Lotus), red osier dogwood (Dogwood), multiflora rose (Multiflora rose), red raspberry (Rubus idaeus), Virginia rose (Rosa virginiana), rose of Sharon (Hibiscus syriacus), staghorn sumac (Rhus typhina) and European bilberry (Viburnum opulus).
When comparing native and introduced plant species, the study found no significant differences in the overall nutritional content of their pollen. This suggests that both native and non-native plants can potentially provide valuable nutritional resources for bee populations.
Bees rely on two main food sources: nectar and pollen. While nectar provides them with carbohydrates and water, pollen is their main source of protein, fat, vitamins, and minerals. Adult bees consume both nectar and pollen, but pollen plays a crucial role in the development of larvae.
When foraging, bees collect pollen using specialized structures on their bodies, such as pollen baskets (called corbiculae) on their hind legs, or scopal hairs on their abdomen or legs, depending on the species. They then carry this pollen back to the hive or nest.
In social bees such as honeybees, workers mix pollen with nectar and their own glandular secretions to create “bee bread,” which is used to nourish the developing larvae. In solitary bees, females provide each brood cell with a mixture of pollen and nectar before laying an egg. This pollen is the sole source of food for the developing larva until it emerges as an adult. Therefore, the nutritional quality of pollen has a direct impact on the health, development, and survival of bee populations.
Bees need a diet rich in specific nutrients, including omega-6 and omega-3 fatty acids. These compounds are essential for bees’ longevity, immune function, and ability to handle environmental stress. However, the balance of these fatty acids is crucial. Too much or too little can impair their cognitive abilities. Additionally, bees need essential amino acids for brain health and reproduction. But there’s a catch: consuming too much of these amino acids can increase their susceptibility to certain parasites. Therefore, a well-balanced diet is essential to maintaining bees’ health and vitality.
The study found that bees need a varied diet from multiple plant sources to obtain a balanced intake of essential fatty acids and amino acids. No single plant species provides pollen with the optimal nutritional profile.
“There is a potential trade-off between the fatty acid and amino acid content of pollen, suggesting that a diverse floral diet may be more beneficial to bees than a single pollen source,” Rehan said. “No single plant species is optimal for the overall health of wild bees.”
When it came to amino acid content, the study found that nearly all plant species contained all ten essential amino acids that bees need in their pollen. However, levels varied considerably between species. Interestingly, pollen from plants in the Asteraceae family (which includes daisies and sunflowers) stood out for its particular richness in essential amino acids. Seven Asteraceae species had levels of essential amino acids exceeding 20% of their total pollen content.
The researchers also looked at protein-to-lipid ratios and omega-6-to-omega-3 fatty acid ratios in the pollen samples, as these are considered important factors in bee nutrition. They found wide variation between species, even within the same plant genus.
“This diversity in pollen nutritional profiles likely allows bees, particularly specialist species, to selectively seek out resources that best meet their unique dietary needs,” the study authors noted.
The study’s findings are particularly relevant given the alarming decline in bee populations worldwide. With more than 3,600 species in the United States and Canada, bees represent a remarkably diverse group of pollinators. However, many bee species face significant threats.
“About 16% of vertebrate pollinators, such as birds and bats, and 40% of invertebrate pollinators, such as bees and butterflies, are threatened with extinction,” according to a comprehensive study published in May in CABI Reviews.
Habitat loss and fragmentation, pathogens and diseases, pesticides, insecticides such as neonicotinoids, herbicides and fungicides used in agriculture and landscaping, invasive species, climate change and competition between honeybees and native bees are some of the reported causes of pollinator decline.
Loss of preferred host plants is a contributing factor in the decline of some bee populations. In addition, the spread of pests and pathogens poses a serious threat to wild and domestic bee species, with the transport of honeybee colonies for commercial pollination often exacerbating this problem.
Bee conservation efforts are multidimensional and involve both large-scale policy changes and individual actions. At the policy level, initiatives include protecting key habitats, regulating pesticide use, and supporting bee health research.
Organizations like the Xerces Society have successfully advocated for protection of several bee species at the federal and state levels. They also work with farmers and land managers to implement bee-friendly practices.
Individuals can also play a crucial role in bee conservation. Planting native flowers, reducing pesticide use, and creating nesting habitats are all effective ways to support local bee populations. Even small actions, like turning part of a lawn into a wildflower meadow or leaving bare patches of soil for ground-nesting bees, can make a significant difference.
Rehan and his colleagues hope their findings will help better choose plant species for pollination gardens and restore habitats. However, they point out that the analysis only included 57 plant species out of thousands that exist.
“We hope this work will help inform the choice of flowering plants for pollinator gardens,” Rehan said. “But here, we only looked at 57 plant species, when there are thousands to look at to understand nutritional profiles. We hope this will inspire similar future research as well as follow-up studies on bee preferences and survival on different diets.”
Banner image of a bee with a sunflower in Tokyo. Image by mrhayata via Flickr (CC BY-SA 2.0).
Liz Kimbrough is a staff writer for Mongabay and holds a PhD in ecology and evolutionary biology from Tulane University, where she studied tree microbiomes. See more of her reporting here.
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Quotes:
Stephen, KW, Chau, KD, & Rehan, SM (2024). Pollinator Dietary Foundations: Plant Nutritional Profiling for Bee Health. Frontiers of sustainable food systems, 81411410. doi:10.3389/fsufs.2024.1411410
Brunet, J., & Fragoso, FP (2024). What are the main reasons for the global decline in pollinator populations? CABI Reviews, 19(1). doi:10.1079/cabireviews.2024.0016
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