Biology subjects

Dolezal, A. G.

Publications and source records attributed to Dolezal, A. G..

6 recordsLinked to original sources

bioRxiv2025

Honey bees (Apis mellifera) exhibit seasonal variation in their tolerance to viral infection

Seasonal variation strongly influences honey bee colony dynamics, leading to time-dependent changes in behavioral and physiological phenotypes. However, the extent to which seasonal fluctuations affect the susceptibility and tolerance of honey bees to viral infection remains largely unexplored. To address this, we conducted a longitudinal study in which adult honey bee workers were collected monthly from research colonies and experimentally infected with Israeli acute paralysis virus (IAPV) over the course of a year. Our results showed significant seasonal variation in the mortality and IAPV load of inoculated bees, with bees challenged during the pre-overwintering period (i.e., fall) exhibiting the highest susceptibility and lowest tolerance to IAPV infection compared to bees challenged in spring, summer, or winter. To investigate factors underlying these seasonal differences, we conducted nutrition-based studies that determined: 1) the variation in lipid content of colonies throughout the year and its potential link to our observed trends in IAPV tolerance, and 2) the impact of seasonally collected pollen on the survivorship of IAPV-challenged bees. Our findings support that seasonal changes in honey bee physiology and nutritional status play key roles in influencing honey bee viral tolerance. We conclude that honey bee colonies are particularly vulnerable to viral infection during the pre-overwintering period, most likely as a result of reduced tolerance to pathogen stress when transitioning from a summer to winter worker population. We further hypothesize that this period of increased vulnerability to viral infection, in correlation with other disease factors such as Varroa mite abundance and available forage, likely contributes to the relatively high overwintering losses experienced by beekeepers. Given the recent reports of severe colony losses attributed to honey bee viruses, understanding the relationship between seasonality and viral tolerance in honey bees is crucial for better informing management strategies and improving overwintering success. AUTHOR SUMMARYWe explored how seasonal changes affect the ability of honey bees to withstand viral infections. Previous research has shown that there are physical and behavioral differences between summer and winter bees, but its unclear how these seasonal differences affect a honey bees ability to withstand viral infection. To investigate this, we collected honey bee workers monthly and infected them with Israeli acute paralysis virus (IAPV) over the course of a year. Our results showed that honey bees were most vulnerable to IAPV in the fall (i.e., prior to overwintering), as they showed the highest mortality rates and lowest viral tolerance, based on their IAPV loads, during this time. By following up with nutrition-based studies, we found that seasonal changes in bee nutrition in part explained the seasonal differences we observed in honey bee virus tolerance. Overall, our findings suggest that bees are less tolerant to viral infection during the pre-overwintering period when colonies transition from a summer to a winter worker population. This vulnerable period may help explain the high rates of colony losses experienced by beekeepers nationwide and demonstrates the importance of developing seasonally-dependent disease management strategies.

pathology↗

bioRxiv2025

Mobile genetic elements exhibit increased sequence diversity with increasing host range within the gut microbiome of the Western Honey bee

Mobile genetic elements (MGEs), such as plasmids and bacteriophages, are major contributors to the ecology and evolution of host-associated microbes due to a continuum of symbiotic interactions and by mediating gene flow via horizontal gene transmission. However, while myriad studies have investigated relationships between MGEs and variation in fitness among microbial and eukaryotic hosts, few studies have incorporated this variation into the context of MGE evolution and ecology. Combining HiC-resolved metagenomics with the model honey bee worker gut microbiome, we show that the worker gut contains a dense, nested MGE community that exhibits a wide degree of host range variation among microbial hosts. Using measures of gene similarity and syntenty, we show that plasmids likely mediate gene flow between individual honey bee colonies, though these plasmids exhibit broad host range variation within their individual microbiomes. We further show that phage-microbe networks exhibit high variation among individual metagenomes, and that phages show broad host range with respect to both the number and phylogenetic distance of their hosts. Finally, we provide evidence that measures of nucleotide variation positively correlate with host range in bee-associated phages, and that functional targets of diversifying selection are partitioning differently between broad or narrow host range phages. Our work underscores the variability of MGE x microbial interactions within host-associated microbial communities and highlights the genomic variation associated with MGE host range diversity.

evolutionary biology↗

bioRxiv2024

Adult honey bee queens consume pollen and nectar

Despite the queens crucial reproductive role in honey bee colonies, queen diet and feeding behavior remain remarkably enigmatic, with most studies assuming they are solely fed nutritious glandular secretions (i.e., royal jelly) by workers. This colors our understanding of basic honey bee biology and how governmental agencies assess pesticide risk. We hypothesized that adult queens also consume honey and pollen. Through experiments with queenright laboratory microcolonies fed with marked diets, we demonstrate that queens are fed pollen and nectar by workers and can also feed directly. We then measured pollen content in mature, unmanipulated queens sacrificed from 43 conventional field colonies from two distinct geographical regions. Similar to workers, we found pollen in almost all queens guts, though at expectedly lower quantities than in young workers. These findings suggest queens have a more complex, dynamic diet than previously thought, raising new questions about how dietary habits and feeding behaviors influence pesticide risk and other aspects of queen biology.

ecology↗

bioRxiv2024

Spatiotemporal, environmental, and behavioral predictors of Varroa mite intensity in managed honey bee apiaries

Honey bees contribute substantially to the world economy through pollination services and honey production. In the U.S. alone, honey bee pollination is estimated to contribute at least $11 billion annually, primarily through the pollination of specialty crops. However, beekeepers lose about half of their hives every season due to disease, insecticides, and other environmental factors. Here, we explore and validate a spatiotemporal statistical model of Varroa destructor mite burden (in mites/300 bees) in managed honey bee colonies, exploring the impact of both environmental factors and beekeeper behaviors. We examine risk factors for Varroa infestation using apiary inspection data collected across the state of Illinois over 2018-19, and we test the models using inspection data from 2020-21. After accounting for spatial and temporal trends, we find that environmental factors (e.g., floral quality, insecticide load) are not predictive of Varroa intensity, while several beekeeper behaviors (e.g., smaller colony density, supplemental feeding, and mite monitoring/treatment) are protective against Varroa. Interestingly, while monitoring and treating for Varroa is protective, treating without monitoring is no more effective than not treating at all. This is an important result supporting Integrated Pest Management (IPM) approaches. Author SummaryHoney bees contribute substantially to the world economy through pollination services and honey production. However, beekeepers lose about half of their hives every season due to disease, insecticides, and other environmental factors. Pathogens, such as Varroa mites and the viruses they vector, are especially detrimental to colony health, and best practices for pest management remain contentious. In this study, we model Varroa destructor mite burden in managed honey bee colonies using apiary inspection data collected across the state of Illinois from 2018 - 2021. Our modelling approach accounts for both spatial and temporal trends, allowing us to investigate the marginal impacts of environmental factors and beekeeper interventions on mite burden. We show that treating for Varroa mites has a protective effect only when accompanied by a monitoring strategy, important evidence in favor of Integrated Pest Management (IPM) approaches.

ecology↗

bioRxiv2024

A honey bee-associated virus remains infectious and quantifiable in postmortem hosts

Corpse-mediated transmission is a potentially viable route through which naive hosts can become infected, but its likelihood for honey bee-associated viruses is largely unknown. While these viruses can be easily detected in deceased bees, it remains unclear if they stay infectious within postmortem hosts or if enough viral RNA degradation--and subsequently virus inactivation--occurs post-host death to render these viruses inviable. This knowledge gap has important implications for how researchers perform honey bee virus studies and for our general understanding of honey bee virus transmission. To better understand the resiliency of honey bee-associated viruses within deceased hosts, we first tested the hypothesis that postmortem specimens, stored in colony-normal temperature and humidity conditions, can be reliably used to quantify virus abundance. To determine this, we experimentally-infected adult honey bees with Israeli acute paralysis virus (IAPV) and then measured the virus levels of individuals sampled live or at different postmortem timepoints (4-, 12-, 24-, and 48-hours post-death) using RT-qPCR and a standard curve absolute quantification method. We found no significant differences based on when bees were sampled, indicating that postmortem honey bees are statistically comparable to using live-sampled bees and can be reliably used to quantify absolute IAPV abundance. We then performed a follow-up experiment that determined whether or not the IAPV detected in postmortem bees remained infectious over time. We found that IAPV extracted from postmortem bees remained highly infectious for at least 48-hours post-death, indicating that any viral RNA degradation that may have occurred during the postmortem interval did not adversely affect IAPVs overall infectivity. The results from this study suggest that IAPV is more resilient to degradation than previously assumed, support the use of postmortem bees for downstream IAPV analyses, and indicate that postmortem hosts can act as sources of IAPV infection for susceptible individuals.

pathology↗

bioRxiv2023

Host species and geography impact bee-associated RNA virus communities with evidence for isolation-by-distance in viral populations

1Virus symbionts are important mediators of ecosystem function, yet we know little of their diversity and ecology in natural populations. The alarming decline of pollinating insects, especially the European honey bee, Apis mellifera, has been driven in part by worldwide transmission of virus pathogens. Previous work has examined the transmission of known honey bee virus pathogens to wild bee populations, but only a handful of studies have investigated the native viromes associated with these bees, limiting epidemiological predictors associated with viral pathogenesis. Further, social variation among different bee species might have important consequences in the acquisition and maintenance of bee-associated virome diversity. We utilized comparative metatranscriptomics to develop a baseline description of the RNA viromes associated with wild bee pollinators and to document the interaction between hymenopteran insect social behavior and virus community composition. Our sampling includes five wild-caught, native bee species that vary in social behavior as well as managed honey bees. We describe 26 putatively new RNA virus species and contrary to our expectations, find few differences in virus diversity or abundance among socially variable bee species. Each bee species was associated with a specific virus community composition, even among sympatric populations of distinct host species. From 17 samples of a single host species, we recovered a single virus species despite over 600 km of distance between host populations and found strong evidence for isolation-by distance in associated viral populations. Our work adds to the small number of studies examining viral prevalence and community composition in wild bees.

bioinformatics↗