Bee Stocks Research Articles

Comparative assessment of food consumption, longevity, thermoregulation, and molecular health markers in mite-resistant and Italian honey bee stocks

Identifying traits for adaptation to different management and environmental regimes is key to maintaining robust honey bee populations under global climate change. We compared mite-resistant (Pol-line and Russian) and Italian honey bee stocks in variable-temperature cage experiments (200 bees per cage) with respect to food consumption, thermoregulation, gene expression, and lifespan, in 3 experiments over 2 years. The Italian stock bees consumed more syrup and pollen on average than the mite-resistant stocks, but the mite-resistant stocks maintained higher cluster temperatures and had median lifespans 8 days longer, consistent with the increased expression of vitellogenin relative to Italian stock. Model results indicated that, to maintain the same colony size as the mite-resistant stocks, Italian stock colonies would need about 13% more sealed brood to offset reduced worker lifespans. These differences among bee stocks likely influence colony-level productivity and health, and showed the importance of experimental replication.

Honey bee stocks exhibit high levels of intra-colony variation in viral loads

Colonies of the western honey bee, Apis mellifera L., are comprised of tens of thousands of genetically related individuals that can easily share and spread pathogens. Honey bee colonies exhibit variations in disease susceptibility that can translate into highly variable pathogen replication among individuals within a colony, between colonies, and between stocks. Here, we investigate the degree of variation in viral titers of common honey bee viruses (DWV-A, DWV-B, IAPV, LSV2, BQCV) within colonies and between colonies of five honey bee stocks in the United States. Our results showed high intra-colony variation in DWV-A, DWV-B, IAPV, and LSV2, but not in BQCV titers. However, the level of variation was not consistent across stocks. Here, we empirically demonstrate that there is significant intra-colony variation in viral titers and that some stocks are more prone to this variability. Our results highlight the need for further studies comparing virus susceptibility among stocks.

Perg reserve and development of bee colonies of different genealogical formations of the carpathian subspecies

The study of bee colony growth patterns throughout the year makes it possible to substantiate the ways of creating strong families that will ensure high productivity in the collection of bee products. The research was conducted on bees of different genealogical formations of the Carpathian breed in private apiaries in the village of Navariya, Lviv region. To conduct the experimental studies, 6 groups of 10 bee colonies were formed: I – the control group – local bees of the Carpathian population (type “Vuchkovsky”); II – the experimental group – inbred group ♀ UA3-5-9-15.112-2018 x ♂ UA3-5-9-15. 112-2018 (♀ microline “915” x ♂ microline “915”); III – experimental group – breeding cross ♀ UA3-65-2019 x ♂ UA3-5-9-15.112-2018 (♀ microline “Sto” x ♂ microline “915”); IV – experimental group – breeding cross ♀ UA3-5-35-2019 x ♂ UA3-5-9-15. 112-2018 (♀ type “Vuchkovsky” x ♂ microline “915”); V – experimental group – breeding cross ♀ UA3-5-307/67-2018 x ♂ UA3-5-9-15. 112-2018 (♀ microline "67" x ♂ microline “915”); VI – experimental group – breeding cross ♀UA3-5-07-2018 x ♂ UA3-5-9-15.112-2018 (♀ microline “07” x ♂ microline “915”). It was established that bees of different breeding crosses of the Carpathian breed had certain differences in the strength of bee colonies, the number of closed broods, and bee bread productivity. The maximum values of bee colony strength and stocks of perga in all groups were noted during the inspection on 10 June. At the same time, the highest value of bee colony strength was observed in the fifth experimental group (19.7 hives), and the best bee colonies in the second experimental group (6992.0 cells) were found in terms of perg productivity. The highest values of the number of closed brood were recorded during the inspection on 29 May, with the bee colonies of the third experimental group prevailing in this respect (20547.6 cells). Thus, to increase the strength of bee colonies, the number of closed brood, and the bee bread productivity, it is advisable to breed interbreed crosses of the Carpathian subspecies since they are superior to local bees of the Vuchkovsky type in the above characteristics.

Phenotypic and genetic characterization of Africanized Apis mellifera colonies with natural tolerance to Varroa destructor and contrasting defensive behavior.

Africanized Apis mellifera colonies with promising characteristics for beekeeping have been detected in northern Argentina (subtropical climate) and are considered of interest for breeding programs. Integral evaluation of this feral material revealed high colony strength and resistance/tolerance to brood diseases. However, these Africanized honeybees (AHB) also showed variable negative behavioral traits for beekeeping, such as defensiveness, tendency to swarm and avoidance behavior. We developed a protocol for the selection of AHB stocks based on defensive behavior and characterized contrasting colonies for this trait using NGS technologies. For this purpose, population and behavioral parameters were surveyed throughout a beekeeping season in nine daughter colonies obtained from a mother colony (A1 mitochondrial haplotype) with valuable characteristics (tolerance to the mite Varroa destructor, high colony strength and low defensiveness). A Defensive Behavior Index was developed and tested in the colonies under study. Mother and two daughter colonies displaying contrasting defensive behavior were analyzed by ddRADseq. High-quality DNA samples were obtained from 16 workers of each colony. Six pooled samples, including two replicates of each of the three colonies, were processed. A total of 12,971 SNPs were detected against the reference genome of A. mellifera, 142 of which showed significant differences between colonies. We detected SNPs in coding regions, lncRNA, miRNA, rRNA, tRNA, among others. From the original data set, we also identified 647 SNPs located in protein-coding regions, 128 of which are related to 21 genes previously associated with defensive behavior, such as dop3 and dopR2, CaMKII and ADAR, obp9 and obp10, and members of the 5-HT family. We discuss the obtained results by considering the influence of polyandry and paternal lineages on the defensive behavior in AHB and provide baseline information to use this innovative molecular approach, ddRADseq, to assist in the selection and evaluation of honey bee stocks showing low defensive behavior for commercial uses.

Melittobia acasta (Hymenoptera: Eulophidae) female longevity and life stage-dependent parasitism using commercially managed Megachile rotundata (Hymenoptera: Megachilidae) as hosts.

Melittobia acasta Walker is one among other hymenopterous parasitoids of Megachile rotundata F. Commercial M. rotundata populations are employed to pollinate North American alfalfa for seed production. This wasp can be prolific when using M. rotundata as a host and can reduce or destroy bee stocks. Hundreds of M. acasta female offspring can develop in a single M. rotundata cell and disperse to infest other cells, producing thousands of more parasitoids. In this study, we determined (i) upon what bee life stages M. acasta females choose to lay eggs and if those eggs ultimately become adults and (ii) M. acasta female longevity when exposed to various resources within M. rotundata cells. We found that M. acasta females lay eggs on M. rotundata prepupae and pupae and that those eggs can hatch and survive to adulthood. Eggs are not laid on early instar bee larvae; eggs laid on adults do not survive. Average female life span is 5 days without feeding, 8-9 days if a pollen-nectar provision is available while the bee develops through larval stages, and 34 days if the wasp can feed on prepupal hemolymph. Wasp females can emerge from bee cells several days after trays of cells are taken to fields. Therefore, adult females could survive long enough for new bee offspring to become prepupae. Our findings support a better understanding of host life stage preference and the longevity of M. acasta females that can inform the timing of the implementation of possible control measures.

Life cycle of Melittobia acasta (Hymenoptera: Eulophidae) using Megachile rotundata (Hymenoptera: Megachilidae) as a host

Abstract Megachile rotundata F. is the primary commercial pollinator for alfalfa seed production in North America. Managed M. rotundata populations are susceptible to several mortality factors including attack by parasitoids. One such parasitoid, Melittobia acasta Walker, is a multivoltine wasp whose infestations can decimate bee stocks. Details of M. acasta life history using M. rotundata as a host are needed to develop control strategies. Our objectives were (i) to describe the M. acasta life cycle using M. rotundata prepupae as hosts and (ii) to determine the M. acasta developmental base temperature and propose a degree-day model. First, 150–300 M. acasta adults were introduced to 60 M. rotundata prepupae (10–20 wasp females/4 bee prepupae) upon which they oviposited. Progeny development (at 30 °C) was monitored through adulthood. We identified 12 distinct phases of the M. acasta life cycle that were observed among samples over an average of 19.5 days. Second, vials each containing a M. rotundata prepupa with M. acasta eggs were positioned across a temperature gradient bar (2 vials per temperature). In repeated trials, wasp development was tracked from egg to adult where a mean development time for 30 °C was found to be 13 days. A linear regression analysis determined the lower developmental temperature threshold to be 8.55 °C. Application of this base temperature in a degree-day model revealed an average of 305.8-degree-day accumulation from egg to adult. These results provide a framework to assist bee managers in devising M. acasta control strategies and timing their implementation.

Tropilaelaps mercedesae Infestation Is Correlated with Injury Numbers on the Brood and the Population Size of Honey Bee Apis mellifera.

Tropilaelaps mercedesae, one of the most devastating parasitic mites of honey bee Apis mellifera hosts, is a major threat to honey products by causing severe damage to honey bee colonies. Here, we recorded injury numbers caused by T. mercedesae to different body parts of the larval, pupal, and crippled adult stages of honey bee A. mellifera. We evaluated the relationship between infestation rate and injury numbers per bee for both larvae and pupae. We also noted the total bee numbers per beehive and examined the relationship between the infestation rate and population size. T. mercedesae infested all developmental stages of honey bees, with the highest injury numbers in the abdomens of bee pupae and the antennas of crippled adult bees. Although larvae received more injury numbers than pupae, both infestation rate and injury numbers decreased as the larval stage progressed to the pupal stage. The infestation rate increased as the population size per beehive decreased. This study provided new perspectives to the understanding of changes in the effects of T. mercedesae infestations on different developmental stages of honey bees. It also showed useful baseline information for screening honey bee stock that might have high defensive behaviors against mite infestation.

Russian honey bee genotype identification through enhanced marker panel set.

Russian honey bees (RHB) are a breeding population developed by USDA-ARS as an effort to provide Varroa-resistant honey bees to beekeepers. The selection strategy for this breeding population was the first in honey bees to incorporate genetic stock identification (GSI). The original GSI approach has been in use for over a decade, and though effective, novel technologies and analytical approaches recently developed provide an opportunity for improvement. Here we outline a novel genotyping assay that capitalizes on the markers used in the GSI as well as new loci recently identified in a whole genome pooled study of commercial honey bee stocks. Our approach utilizes a microfluidic platform and machine learning analyses to arrive at an accurate, high throughput assay. This novel approach provides an improved tool that can be readily incorporated into breeding decisions towards healthier more productive bees.

Viral species differentially influence macronutrient preferences based on honey bee genotype.

ABSTRACTFood quantity and macronutrients contribute to honey bee health and colony survival by mediating immune responses. We determined if this held true for bees injected with chronic bee paralysis virus (CBPV) and deformed wing virus (DWV), two common honey bee ssRNA viruses. Pollen-substitute diet and syrup consumption rates and macronutrient preferences of two Varroa-resistant stocks (Pol-Line and Russian bees) were compared to Varroa-susceptible Italian bees. Bee stocks varied in consumption, where Italian bees consumed more than Pol-Line and Russian bees. However, the protein: lipid (P:L) ratios of diet consumed by the Italian and Russian bees was greater than that of the Pol-Line bees. Treatment had different effects on consumption based on the virus injected. CBPV was positively correlated with syrup consumption, while DWV was not correlated with consumption. P:L ratios of consumed diet were significantly impacted by the interaction of bee stock and treatment, with the trends differing between CBPV and DWV. Variation in macronutrient preferences based on viral species may indicate differences in energetic costs associated with immune responses to infections impacting different systems. Further, virus species interacted with bee genotype, indicating different mechanisms of viral resistance or tolerance among honey bee genotypes.

Phosphoproteomics analysis of hypopharyngeal glands of the newly emerged honey bees (Apis mellifera ligustica)

The most important honey bee queen food royal jelly is produced by the exocrine hypopharyngeal glands (HGs) of the worker honey bees. The HGs exhibits diverse gene and protein that create age-related physiological adaptations. However, limited knowledge is available on how the phosphorylation process is responsible for physiological alterations across the development of HGs in newly emerged bees. This study measured the acinus of HGs and characterized its phosphoproteomics analysis between the newly emerged bees of royal jelly bees (RJBs) and Italian bees (ITBs). Phosphopeptides of HGs were enriched by Ti4+-IMAC reagents, followed by protein identification via Q-Exactive LC-MS/MS. Our findings indicated that the mean acinus size of HGs of newly emerged bees of RJBs was significantly larger (56.18 ± 1.72 µm) than ITBs (45.98 ± 1.62 µm). A total of 1576 phosphopeptides with 1800 phosphosites containing 525 phosphoproteins were identified in RJBs, while 746 phosphopeptides, of which 846 phosphosites correspond to 317 phosphoproteins were identified in ITBs. Most proteins were phosphorylated on 1 residue followed by 2 and 3 residues in newly emerged bees of both bee stocks. In addition, serine phosphorylation was most observed, followed by threonine and tyrosine in both bee stocks. In newly emerged bees of RJBs, the protein metabolic process, glycolytic process, and formation of translation preinitiation were uniquely enriched, while protein translation, peptide metabolic process and elongation were enriched in ITBs. This research shows detailed phosphorylation of HGs and provides helpful information for understanding the biological activities of HGs development in newly emerged bees from both bee stocks.

Honey Bee Genetic Stock Determines Deformed Wing Virus Symptom Severity but not Viral Load or Dissemination Following Pupal Exposure.

Honey bees exposed to Varroa mites incur substantial physical damage in addition to potential exposure to vectored viruses such as Deformed wing virus (DWV) that exists as three master variants (DWV-A, DWV-B, and DWV-C) and recombinants. Although mite-resistant bees have been primarily bred to mitigate the impacts of Varroa mites, mite resistance may be associated with increased tolerance or resistance to the vectored viruses. The goal of our study is to determine if five honey bee stocks (Carniolan, Italian, Pol-Line, Russian, and Saskatraz) differ in their resistance or tolerance to DWV based on prior breeding for mite resistance. We injected white-eyed pupae with a sublethal dose (105) of DWV or exposed them to mites and then evaluated DWV levels and dissemination and morphological symptoms upon adult emergence. While we found no evidence of DWV resistance across stocks (i.e., similar rates of viral replication and dissemination), we observed that some stocks exhibited reduced symptom severity suggestive of differential tolerance. However, DWV tolerance was not consistent across mite-resistant stocks as Russian bees were most tolerant, while Pol-Line exhibited the most severe symptoms. DWV variants A and B exhibited differential dissemination patterns that interacted significantly with the treatment group but not bee stock. Furthermore, elevated DWV-B levels reduced adult emergence time, while both DWV variants were associated with symptom likelihood and severity. These data indicate that the genetic differences underlying bee resistance to Varroa mites are not necessarily correlated with DWV tolerance and may interact differentially with DWV variants, highlighting the need for further work on mechanisms of tolerance and bee stock–specific physiological interactions with pathogen variants.

Examining Historical Rates of Leafcutting Bee Brood Cell Pathogens, Parasitoids, and Predators to Establish Baseline Infectivity Rates for Alfalfa Seed Growers.

The alfalfa leafcutting bee Megachile rotundata (Fabricius) (Hymenoptera: Megachilidae) is the primary pollinator for the alfalfa seed industry. It is a solitary cavity nesting bee that utilizes leaf lined brood cells provisioned with pollen for larval development and pupation into the adult stage. During development, multiple pathogens, parasitoids, and predators can prey upon or use the larvae as a host, resulting in the loss of the future adult bee. As such, the presence of invertebrate pests and fungal pathogens presents a major concern for commercial alfalfa seed growers. In the present study, we used historic data from the Parma Cocoon Diagnostic Laboratory to determine baseline rates of pathogens, parasitoids, and predators of Megachile rotundata brood cells and used this analysis to determine cutoffs for management practices to inform growers when the purchase of new bee stocks should be considered. Additionally, we compared the presence of chalkbrood, predators, and parasitoids in samples collected from both grower-produced stocks and newly purchased Canadian bees. The results of the investigation provide historic averages of the presence of chalkbrood, predators, and parasitoids, show a significant increase in chalkbrood and predators in 2007–2011, and find a significant difference in rates of chalkbrood and predators between samples from Canadian suppliers and grower stocks. We speculate that these differences may have resulted from economic conditions that increased the cost of Canadian Megachile rotundata cells and likely resulted in increased reliance on 2nd-year U.S. grower stocks and subsequently increased infection rates during this time period.

A derived honey bee stock confers resistance to Varroa destructor and associated viral transmission

The ectoparasite Varroa destructor is the greatest threat to managed honey bee (Apis mellifera) colonies globally. Despite significant efforts, novel treatments to control the mite and its vectored pathogens have shown limited efficacy, as the host remains naïve. A prospective solution lies in the development of Varroa-resistant honey bee stocks, but a paucity of rigorous selection data restricts widespread adoption. Here, we characterise the parasite and viral dynamics of a Varroa-resistant honey bee stock, designated ‘Pol-line’, using a large-scale longitudinal study. Results demonstrate markedly reduced Varroa levels in this stock, diminished titres of three major viruses (DWV-A, DWV-B, and CBPV), and a two-fold increase in survival. Levels of a fourth virus that is not associated with Varroa—BQCV—do not differ between stocks, supporting a disruption of the transmission pathway. Further, we show that when decoupled from the influence of Varroa levels, viral titres do not constitute strong independent predictors of colony mortality risk. These findings highlight the need for a reassessment of Varroa etiology, and suggest that derived stocks represent a tractable solution to the Varroa pandemic.

Evaluation of queen cell acceptance and royal jelly production between hygienic and non-hygienic honey bee (Apis mellifera) colonies.

Honey bees are crucial for pollination services globally and produce important hive products including honey, royal jelly, pollen, and propolis that are being used commercially in food, cosmetics, and alternative medicinal purposes. Among the bee products, royal jelly (RJ) has long attracted scientists' interest because of its importance in honey caste differentiation. The present research was carried out to determine the acceptance rate of queen cells, and RJ production between the hygienic and non-hygienic lines. Further, this study unveils the effect of pollen substitute diets on the queen cell acceptance rate and RJ yields between both bee stocks. Results showed that the uncapped brood cells and dead brood's removal percentage was significantly more in hygienic bee colonies in comparison to non-hygienic bee colonies (p < 0.05). The average percentage of larval acceptance was statistically higher in hygienic lines (64.33 ± 2.91%) compared to non-hygienic lines (29.67 ± 1.20%). Similarly, the RJ mean weight per colony differed statistically between both bee stocks (p<0.001), which were 12.23 ± 0.52 g and 6.72 ± 0.33 g, respectively. Moreover, our results demonstrated that a significant difference was observed in larval acceptance rate, RJ yields (per colony and per cup) between both bee stocks those fed on various diets. However, no significant difference was recorded in RJ yields (per colony and per cup) between both bee stock that feeds on either commercially available pollen or pollen substitute. This study may provide future applications in helping bee breeders to choose the bees that carry a higher level of hygienic behavior with high RJ production traits.

The payoffs and tradeoffs of hygienic behavior: a five year field study on a local population of honey bees

Honey bees are exposed to a variety of risk factors, among which the ectoparasitic mite Varroa destructor and its associated viruses are considered to be the most significant problem worldwide. It has been widely recognized that honey bee stocks resistant to mites are an essential part of any sustainable long-term management of Varroa. The aim of this study was to evaluate the efficacy of hygienic behavior in a local population of honey bees in reducing Varroa infestation. A bi-directional selection for high and low rates of hygienic behavior was carried out in Israel using either artificially inseminated or naturally mated queens. Colonies were screened for performance including population size, honey production, levels of Varroa infestation, and the level of hygienic behavior. Furthermore, we examined the costs and benefits of the selection, and possible trade-offs, using the above measurements of colony performance to ensure their productivity. The selection process revealed that the trait is heritable. The maternal phenotype has a significant effect on Varroa load, as colonies founded by hygienic daughter queens showed a significantly lower parasite load. No major trade-offs were found between the rate of hygienic behavior, honey yield, and population size. Measuring the direct benefits of hygienic behavior through colony performance suggests that breeding for this trait makes bees more resistant to Varroa destructor. These results are promising for our successful local bee breeding programs in a Mediterranean climate.

Differential Expression of Three Dopamine Receptors in Varroa-Resistant Honey Bees.

Various stocks of honey bees (Apis mellifera L. (Hymenoptera: Apidae)) employ multiple mechanisms to control varroa mite (Varroa destructor Anderson & Trueman (Mesostigmata: Varroidae)) infestations. Identification of trait-associated genes and markers can improve efficiency of selective breeding. Dopamine receptors show promise in this regard in their association with numerous traits in honey bees, high plasticity, and indicated association with varroa resistance through QTL analysis. We assessed the relationship between exposure to mite-infested brood and gene expression of the honey bee dopamine receptors, Amdop1, Amdop2, and Amdop3, in bees and stocks with known levels of varroa resistance, in Spring 2016 (VSH vs Italian) and Summer 2019 (Pol-line vs Italian). Relative mRNA expression levels varied both by honey bee stock and before/after exposure to varroa-infested brood, in 7-, 10-, and 14-day-old bees. However, the trials revealed contrasting patterns in expression of the three dopamine receptors. In 2016, downregulation was evident in VSH bees, but varied by days post-emergence and by gene. The 2019 trial showed upregulation post-exposure in both stocks, and at all ages, for Amdop1, Amdop2, and Amdop3, with the exception of 14 d Italian bees for Amdop2 and Amdop3. Stock comparison in 2019 showed upregulation of all three dopamine-like receptors in post-exposure bees of all ages. Season and associated differences in mite loads may have contributed to the differences observed across trials. Differential expression of all three dopamine receptors suggests a role for the dopaminergic system in varroa resistance and suggests that further characterization of these receptors for breeding potential is warranted.

Genetic Variation in Antimicrobial Activity of Honey Bee (Apis mellifera) Seminal Fluid

Honey bees can host a remarkably large number of different parasites and pathogens, and some are known drivers of recent declines in wild and managed bee populations. Here, we studied the interactions between the fungal pathogen Nosema apis and seminal fluid of the Western honey bee (Apis mellifera). Honey bee seminal fluid contains multiple antimicrobial molecules that kill N. apis spores and we therefore hypothesized that antimicrobial activities of seminal fluid are genetically driven by interactions between honey bee genotype and different N. apis strains/ecotypes, with the virulence of a strain depending on the genotype of their honey bee hosts. Among the antimicrobials, chitinases have been found in honey bee seminal fluid and have the predicted N. apis killing capabilities. We measured chitinase activity in the seminal fluid of eight different colonies. Our results indicate that multiple chitinases are present in seminal fluid, with activity significantly differing between genotypes. We therefore pooled equal numbers of N. apis spores from eight different colonies and exposed subsamples to seminal fluid samples from each of the colonies. We infected males from each colony with seminal fluid exposed spore samples and quantified N. apis infections after 6 days. We found that host colony had a stronger effect compared to seminal fluid treatment, and significantly affected host mortality, infection intensity and parasite prevalence. We also found a significant effect of treatment, as well as a treatment × colony interaction when our data were analyzed ignoring cage as a blocking factor. Our findings provide evidence that N. apis-honey bee interactions are driven by genotypic effects, which could be used in the future for breeding purposes of disease resistant or tolerant honey bee stock.

Comparative assessment of various supplementary diets on commercial honey bee (Apis mellifera) health and colony performance.

A healthy honey bee stock is critical to the beekeeping industry and the sustainability of the ecosystem. The quality of the supplemental diet influences the development and strength of the colony, especially during the pollen dearth period in the surrounding environment. However, the extent to which pollen substitute protein feeding affects honey bee colony parameters is not fully known. We conducted this study to test the influence of various supplemental diets on foraging effort, pollen load, capped brood area, population density, and honey yield. The treatment groups were supplied with patties of pollen substitute diets, whereas sugar syrup was given to the control group. Our results indicated that honey bees consumed a significantly higher amount of Diet 1 (45 g soybean flour + 15 g Brewer's yeast + 75 g powdered sugar + 7.5 g skimmed milk + 7.5 g date palm pollen + 200 mL sugar syrup supplement with Vitamin C) followed by others supplemented diets. Further, pollen load, worker-sealed brood area, population strength, and honey yield differed significantly when Diet 1 was consumed instead of other supplemental diets. The proportion of biological parameters was less in the control group as compared to other treatments. This study highlights the potential of supplemental diets to improve the bee's health and colony development when the pollens availability and diversity are insufficient.

Multi-tiered analyses of honey bees that resist or succumb to parasitic mites and viruses

BackgroundVarroa destructor mites, and the numerous viruses they vector to their honey bee hosts, are among the most serious threats to honey bee populations, causing mortality and morbidity to both the individual honey bee and colony, the negative effects of which convey to the pollination services provided by honey bees worldwide. Here we use a combination of targeted assays and deep RNA sequencing to determine host and microbial changes in resistant and susceptible honey bee lineages. We focus on three study sets. The first involves field sampling of sympatric western bees, some derived from resistant stock and some from stock susceptible to mites. The second experiment contrasts three colonies more deeply, two from susceptible stock from the southeastern U.S. and one from mite-resistant bee stock from Eastern Texas. Finally, to decouple the effects of mites from those of the viruses they vector, we experimentally expose honey bees to DWV in the laboratory, measuring viral growth and host responses.ResultsWe find strong differences between resistant and susceptible bees in terms of both viral loads and bee gene expression. Interestingly, lineages of bees with naturally low levels of the mite-vectored Deformed wing virus, also carried lower levels of viruses not vectored by mites. By mapping gene expression results against current ontologies and other studies, we describe the impacts of mite parasitism, as well as viruses on bee health against two genetic backgrounds. We identify numerous genes and processes seen in other studies of stress and disease in honey bee colonies, alongside novel genes and new patterns of expression.ConclusionsWe provide evidence that honey bees surviving in the face of parasitic mites do so through their abilities to resist the presence of devastating viruses vectored by these mites. In all cases, the most divergence between stocks was seen when bees were exposed to live mites or viruses, suggesting that gene activation, rather than constitutive expression, is key for these interactions. By revealing responses to viral infection and mite parasitism in different lineages, our data identify candidate proteins for the evolution of mite tolerance and virus resistance.

Nutrigenetic comparison of two Varroa-resistant honey bee stocks fed pollen and spirulina microalgae

We tested the influence of genetic variation on responses to natural and artificial diets in Varroa-resistant Pol-line and Russian honey bee stocks. Newly emerged workers from six colonies per stock were fed pollen, spirulina (blue-green microalgae), and sucrose-only diets in 144 total cages. Diet type had a strong effect on sugar intake, body weight, fat body lipid content, and vitellogenin (vg) expression. Spirulina consumption was approximately half that of pollen, but led to higher head weights, equivalent thorax weights and vg levels, and marginally reduced fat body lipids. Bee stock and colony had a significant impact on nutritional response. Despite equivalent diet intakes, Pol-line bees accumulated higher lipid levels and consumed less sugar overall than Russian bees. Furthermore, pollen-fed bees sourced from Pol-line colonies had significantly higher vg levels. These differences in nutrient and energy allocation may reflect life history-related physiological tradeoffs. Our results suggest that genotype-dependent nutritional responses are present in honey bees, with promising implications for breeding efforts and tailored approaches to diet and health in a changing global climate.