Farming, urban expansion, and climate change have significantly changed the habitats that are available to bees, crucial pollinators that underpin agriculture — but do these habitats provide the foods that the bees need to survive? Scientists studied the nutritional content of different pollens to determine which plants bees need to eat a healthy diet. They found that the key is access to many different plants, and that non-native species can be equally healthy options. Roses, clover, raspberries, and buttercups are particularly beneficial.

As critical pollinators, bees keep our agricultural systems going — but human-caused changes to the planet heavily impact their foraging options. To help protect our food security, we need more information about bees’ own dietary requirements. Scientists writing in studied the nutritional value of 57 types of pollen and found that bees need to forage from a variety of plants to balance their diet between fatty acids and essential amino acids.

“Despite public interest and a rise in pollinator plantings, little is known about which plant species are best suited for bee health,” said Dr Sandra Rehan of �첥��Ƶ, senior author. “This study aimed to better understand the nutritional value of plant species. Based on their ideal protein to lipid ratios for wild bee nutrition, we recommend that pollen species from roses, clovers, red raspberry, and tall buttercup should be emphasized in wildflower restoration projects.”

The bees’ needs

Pollen and bees are heavily interdependent: plants need bees to spread their pollen to reproduce, and bees need pollen to eat. While bees get their carbohydrates from nectar, pollen provides proteins, lipids, and other critical nutrients. Anthropic changes to the environment which alter the availability and the properties of pollen risk malnourished bees.

Bees especially need to consume high-quality foods containing non-esterified fatty acids like omega-6 and omega-3. Without these nutrients, bees live shorter lives, have weaker immune systems, and are less able to cope with environmental stressors — but if bees consume them in the wrong ratio, they experience cognitive problems. Bees also need essential amino acids, which are necessary for cognitive health and reproduction — but if they eat too much, they may be more susceptible to certain parasites.

To understand which plants are best for bees, the scientists collected pollen samples from 57 species found in North America, either from fresh flowers in the wild or from flowers dried in the lab. They chose the plant species based on their importance to species of wild northeastern bee and their prevalence. The pollen was processed and analyzed for levels of different amino acids, non-esterified fatty acids, and protein to lipid and omega-6:3 ratios, to determine which plants were best for bees.

The scientists also investigated whether closely related species of plant provided similar nutritional benefits, and whether species that had been introduced to the area where they were collected were less nutritious than endemic species.

Healthy eating habits

In general, plants from the same family offered bees quite different nutrients compared to other members of the same family, with the exception of essential amino acids. Plants from the cabbage family, the legume family, and the daisy family all had similar levels of essential amino acids compared to other plants within the same family. Daisies, a very important plant for foraging bees, boasted particularly high levels of essential amino acids. Interestingly, plants that were high in essential amino acids were relatively low in non-esterified fatty acids, and vice versa.

“There is a potential tradeoff between fatty acid and amino acid content within pollen, suggesting that a diverse floral diet may benefit bees more than a single pollen source,” said Rehan. “No one plant species is optimal for generalist wild bee health.”

The scientists’ results indicated that feeding from many different flowers is best for most bees, and that feeding from endemic species of plant offers no nutritional advantage. Most pollen species contain most of the necessary nutrients, but to get the optimal levels of nutrients in their diets, bees would need to forage from several different plant species. The scientists suggested that this diversity of nutritional content reflects the diverse needs of different species of bees, especially the specialist species that favor particular plants. A wide variety of sources of nutrition with different properties means that all bees can forage on the plants that feed them best.

“We hope this work will help inform flowering plant selections for pollinator gardens,” said Rehan. “But here we examined only 57 plant species, and there are thousands to examine to understand nutritional profiles. We hope this will inspire future similar research as well as follow up studies on the preference and survival of bees on different diets.”

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It’s not a single pesticide or virus stressing honey bees, and affecting their health, but exposure to a complex web of multiple interacting stressors encountered while at work pollinating crops, found new research out of �첥��Ƶ.

Scientists have been unable to explain increasing colony mortality, even after decades of research examining the role of specific pesticides, parasitic mites, viruses or genetics. This led the research team to wonder if previous studies were missing something by focussing on one stressor at a time.

“Our study is the first to apply systems level or network analyses to honey bee stressors at a massive scale. I think this represents a paradigm shift in the field because we have been so focussed on finding the one big thing, the smoking gun,” says corresponding author of the new paper York Faculty of Science Professor , York Research Chair in Genomics. “But we are finding that bees are exposed to a very complicated network of stressors that change quickly over time and space. It's a level of complexity that we haven't thought about before. To me, that's the big surprise of this study.”

The paper, , published today in Current Biology, takes a much broader look at the interplay of stressors and their effects. The study team also included researchers from the University of British Columbia, Agriculture and Agri-Food Canada, the University of Victoria, the University of Lethbridge, the University of Manitoba, l'Université Laval, the University of Guelph, and the Ontario Beekeepers' Association.

Not all stressors are the same, however. Some stressors are more influential than others – what researchers call the social media influencers of the bee world – having an outsized impact on the architecture of a highly complex network and their co-stressors. They also found that most of these influencer stressors are viruses and pesticides that regularly show up in combination with specific other stressors, compounding the negative effects through their interactions.

“Understanding which stressors co-occur and are likely to interact is profoundly important to unravelling how they are impacting the health and mortality of honey bee colonies,” says lead author, York Postdoctoral Fellow Sarah French of the Faculty of Science.

“There have been a lot of studies about major pesticides, but in this research, we also saw a lot of minor pesticides that we don’t usually think about or study. We also found a lot of viruses that beekeepers don’t typically test for or manage. Seeing the influencer stressors interact with all these other stressors, whether it be mites, other pesticides or viruses, was not only interesting, but surprising.”

French says the way influencer stressors co-occur with other stressors is similar to the way humans experience co-morbidities, such as when someone is diagnosed with heart disease. They are more likely to also have diabetes or high blood pressure or both, and each one impacts the other. “That’s similar to the way we examine bee colonies. We look at everything that's going on in the colony and then compare or amalgamate all the colonies together to look at the broader patterns of what is happening and how everything is related. Two or multiple stressors can really synergize off each other leading to a much greater effect on bee health.”

From Québec to British Columbia, honey bee colonies were given the job of pollinating some of Canada’s most valuable crops – apples, canola oil and seed, highbush and lowbush blueberry, soybean, cranberry and corn. The study covered multiple time scales, providing numerous snapshots, rather than the usual single snapshot in time. The research team found that honey bees were exposed to an average of 23 stressors at once that combined to create 307 interactions.

Honey bees are a billion dollar industry. In 2021, honey bees contributed some $7 billion in economic value by pollinating orchards, vegetables, berries and oil seeds like canola, and produced 75 to 90 million pounds of honey. Figuring which stressors would provide the most benefit if managed would go a long way toward developing the right tools to tackle them, something beekeepers are often lacking.

The research is part of the project funded to the tune of $10 million by Genome Canada in 2018 to use genomic tools to develop a new health assessment and diagnosis platform powered by stressor-specific markers.

More research is needed to unravel how the stressors are interacting and impacting honey bee mortality and colony health going forward, says French. “It's really teasing apart which of these compounds might have that relationship and how can we build off this to study those specific relationships.”

It can’t come soon enough, honey bees are currently facing poor health, colony loss, parasites, pathogens and heightened stressors worldwide. Some beekeepers in this country and the United States face a loss over winter of up to 60 per cent of their colonies.

“Our study suggests some combinations are occurring very frequently,” adds Zayed, “and that is relevant because we see them again and again, but we don't know how these combinations affect bee health. It helps to prioritize which experiments we can now take back to the lab and establish how these interactions affect bees.”

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More than 30 scientists presented at BeeCon; select recordings of their presentations will be made available on the . Professor Kevin Matteson of the Department of Biology at Miami University presented a keynote talk entitled “Pollinator Conservation in Cities.” .

Amidst various threats endangering bee populations, collaboration between bee researchers and academics plays a pivotal role in safeguarding pollinators worldwide. BEEc promotes collaborative and innovative research, aiming to advance policy changes essential for the conservation and evolution of bees. By offering free attendance, BeeCon serves as a platform where researchers can disseminate advances in bee research globally and foster a positive impact for the future.

BeeCon 2023 was sponsored by the Office of the Vice President of Research and Innovation, the Faculty of Environmental and Urban Change, and the Faculty of Science.

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Media Release from September 14, 2023

�첥��Ƶ researchers examined the early and late life stages of small developing carpenter bees in the presence and absence of maternal care and were surprised by the results.

Most wild bees are solitary, but one tiny species of carpenter bees fastidiously cares for and raises their offspring, an act that translates into huge benefits to the developing bee’s microbiome, development and health, found �첥��Ƶ researchers.

Not unlike the positive effect human mothers can have on their offspring, the maternal care of these carpenter bees (Ceratina calcarata) staves off an overabundance of harmful fungi, bacteria, viruses and parasites in the earliest stage of development.

Without maternal care the pathogen load of these developing bees ballooned – 85 per cent of were fungi, while eight per cent were bacteria – which can impact their microbiome, a critical component of bee health, as well as their development, immune system and gene expression. This can lead, for example, to changes in brain and eye development, and even behaviour. The biggest single fungus found was Aspergillus, known to induce stonebrood disease in honey bees, which mummifies the offspring. In later stages, the lack of care can lead to a reduced microbiome, increasing susceptibility to diseases and poor overall health.

The researchers looked at four overall developmental stages in the life of these carpenter bees starting with the larvae stage both in the presence and absence of maternal care.

“There are fitness affects resulting from these fungal infections. We are documenting the shifts in development, the shifts in disease loads, and it is a big deal because in wild bees there is a lot less known about their disease loads. We are highlighting all of these factors for the first time,” says senior author Sandra Rehan, a professor in York’s Faculty of Science.

The developmental changes sparked by which genes were expressed or supressed, upregulated or downregulated, along with disease loads, depending on the presence or lack of maternal care, created knock-on effects on the microbiome and bee health. These single mothers build one nest a year in the pith of dead plant stems where they give birth and tend to their offspring from spring to as late as fall. Anything that prevents the mother from caring for her young, increases risks of nest predation and parasitism, including excessive pruning of spring and fall stems, and can have huge consequences on their young.

The paper, , was published today in the journal Communications Biology. Lead author Katherine Chau of �첥��Ƶ is a Mitacs Elevate and Weston Family Foundation Microbiome Initiative postdoctoral fellow.

“We found really striking shifts in the earliest stages, which was surprising as we did not expect that stage to be the most significantly changed,” says Chau. “Looking at gene expression of these bees you can see how the slightest dysregulation early in development cascades through their whole formation. It is all interconnected and shows how vital maternal care is in early childhood development.”

This study provides metatranscriptomic insights on the impact of maternal care on developing offspring and a foundational framework for tracking the development of the microbiome. “It is a complex paper that provides layers of data and shows the power of genomics as a tool,” says Rehan. “It allows us to document the interactions between host and environment. I think that is the power of this approach and the new technologies and techniques that we are developing.”

She also hopes it will give people more insight into the hidden life of bees and their vast differences, but also similarities. “Often people see bees as a monolith, but when you understand the complexity of bees and that there are wild bees and managed bees, people are more likely to care about bee diversity,” says Rehan.

Additional authors on the paper are Mariam Shamekh, a former honors thesis student and a Natural Sciences and Engineering Research Council of Canada (NSERC) Undergrad Student Research Award recipient and Jesse Huisken, a PhD candidate and a NSERC Postgraduate scholarship recipient.

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PhD student Kathleen Dogantzis is among three �첥��Ƶ graduates receiving this year’s Governor General Gold Medals, which recognize the outstanding scholastic achievements of graduate students in Canada.

Dogantzis earned a PhD in biology, following the completion of a master of science at �첥��Ƶ. Both degrees were done under the supervision of Professor Amro Zayed and saw Dogantzis’ work focus on honey bees and their importance, as well as their complex history as pollinators. Her dissertation – “Understanding the evolutionary origin and ancestral composition of honey bee (Apis mellifera) populations” – sought to gain a deeper understanding of the genetic composition of honey bee populations in order to make more informed decisions about their health and sustainable beekeeping.

Furthermore, Dogantzis’ research involved the development of molecular tools capable of genetically detecting Africanized bees, which are essential in biosecurity as they can help monitor the movement of populations and ensure the sustainability of apiculture practices in Canada and abroad.

“I am honoured to have been nominated and selected for this prestigious award. It means a great deal to me for my work to be recognized. My achievements would not have been possible without the support, mentorship, and contributions from my advisor and colleagues,” Dogantzis says, who looks forward to applying the skills, experiences and values she gained at York to a future role focused on sustainability.

Read the full .

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Wild bees living in cities like Toronto are facing increased environmental stressors compared to those in rural and even suburban areas, such as more pathogens and parasites, found researchers at �첥��Ƶ.

They also found changes in the microbiomes of wild bees living in densely urban areas and fragmented habitats, which makes it more difficult for the bees to access food sources, ideal nesting areas and mates.

These environmental stressors will likely increase in the future as cities expand and landscapes are reshaped, posing one of the largest threats to the natural ecosystems of wild bees and their biodiversity. Two-thirds of the world’s population are expected to live in cities by 2050.

“Having less connected habitats in dense urban areas not only leads to more inbreeding, so less genetic diversity, but it also creates higher pathogen diversity leaving city bees exposed to more pathogens,” says Corresponding author and Associate Professor of the Faculty of Science, �첥��Ƶ.

The researchers used whole genome sequencing of 180 common carpenter bees – Ceratina calcarata – to look at their population genetics, metagenome and microbiome, as well the impact of environmental stressors across the Greater Toronto Area. These small carpenter bees are wild and native bees, not managed and non-native bees, such as a honeybees.

They also found significant environmental variation in bee microbiomes and nutritional resources even in the absence of genetic differentiation.

“Parasite and pathogen infections in bees are a major driver in global bee population declines and this is further exacerbated by urbanization and a loss of habitat and degraded habitat. There are things, though, that cities could do to help wild bees,” says lead author York PhD student Katherine D. Chau.

“We found the best way to connect bee habitats and create conditions for more genetic diversity is through green spaces, shrubs and scrub. Conservation efforts focussed on retaining and creating these habitat connectors could go a long way toward helping wild bee health.”

Although bees are the most prominent pollinators, cities could impact all insect pollinators, which pollinate more than 87 per cent of flowering plants and 75 per cent of food crops globally. Cities, unlike rural areas, also create an urban heat island effect – higher temperatures in the city than those in the surrounding areas – and this affects flowering times and growing season length. This could lead to flowers, for example, blooming before or after bees are out and foraging.

The higher number of pathogen and parasite infections in urban areas can also be attributed to disease spill over. Because the bees are concentrated in certain areas, infected bees are more likely to contaminate the flowers they visit, which then spreads the infection to the next bee that visits that flower, even across bee species, say the researchers.

“Our research is the first known whole genome sequencing, population genomic and metagenomic study of a wild, solitary bee in an urban context, which looks at the complex relationship between bees, metagenomic interactions and dense urban landscapes,” says Rehan. “This approach provides a tool to assess not only the overall health of wild bees in urban settings but could also be applied across a broad range of wildlife and landscapes.”

Now that several known bee and plant pathogens have been identified in dense urban areas, the researchers say it paves the way for early detection and monitoring of threats to wildlife in cities.

“Future studies should explore the link between reduced genetic diversity and the fitness of wild bees in cities,” says Chau.

The paper, , was published in the journal Global Change Biology.

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BeeCon is a free, annual conference that brings together bee biologists on a global scale to discuss bees, collection methods, pollination, genomics, conservation and behaviour. This year’s BeeCon welcomed bee researchers and community members from 47 countries spanning six continents. BeeCon took place Oct. 13 and 14.

This year’s conference featured keynote speaker, Professor Hollis Woodard of the Department of Entomology at the University of California. Woodard presented a talk titled, “The Ontogeny of Sociality in Bumble Bee Queens.” A YouTube recording of the Woodward’s presentation can be .

With bee populations being threatened by a host of factors, the collaborative efforts of bee researchers and academics are vital in preserving pollinator populations worldwide. BEEc fosters collaborative and innovative research to advance policy changes to sustain bee evolution and conservation. Through BeeCon’s free attendance, researchers can share cutting-edge findings on a global scale, creating positive change for the future.

The 2022 BeeCon was sponsored by the Office of the Vice President of Research and Innovation, the Faculty of Environmental and Urban Change and the Faculty of Science.

Recordings of select BeeCon presentations are available and can be viewed on the , subscribers to the channel can receive a notification when new videos are uploaded.

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