91亚色 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.

TORONTO, Sept. 14, 2023 鈥� 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鈥檚 microbiome, development and health, found 91亚色 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 鈥� 85 per cent of were fungi, while eight per cent were bacteria 鈥� 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.

鈥淭here 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,鈥� says senior author Sandra Rehan, a professor in 91亚色鈥檚 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 91亚色 is a Mitacs Elevate and Weston Family Foundation Microbiome Initiative postdoctoral fellow.

鈥淲e found really striking shifts in the earliest stages, which was surprising as we did not expect that stage to be the most significantly changed,鈥� says Chau. 鈥淟ooking 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.鈥�

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. 鈥淚t is a complex paper that provides layers of data and shows the power of genomics as a tool,鈥� says Rehan. 鈥淚t 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.鈥�

She also hopes it will give people more insight into the hidden life of bees and their vast differences, but also similarities. 鈥淥ften 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,鈥� 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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TORONTO, May 16, 2023 鈥� 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 91亚色.

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鈥檚 population are expected to live in cities by 2050.

鈥淗aving 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,鈥� says Corresponding author and Associate Professor of the Faculty of Science, 91亚色.

The researchers used whole genome sequencing of 180 common carpenter bees 鈥� Ceratina calcarata 鈥� 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.

鈥淧arasite 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,鈥� says lead author 91亚色 PhD student Katherine D. Chau.

鈥淲e 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.鈥�

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 鈥� higher temperatures in the city than those in the surrounding areas 鈥� 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.

鈥淥ur 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,鈥� says Rehan. 鈥淭his 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.鈥�

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.

鈥淔uture studies should explore the link between reduced genetic diversity and the fitness of wild bees in cities,鈥� says Chau.

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

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