Eastern Honey Bee Apis Cerana Research Articles

Ecotoxicological effects of common fungicides on the eastern honeybee Apis cerana cerana (Hymenoptera)

The widespread use of fungicides for plant protection has increased the potential for pollinator exposure. This study therefore aimed at assessing the acute and chronic effects of fungicides on pollinators. For this purpose, the acute oral toxicity of the common fungicides azoxystrobin, pyraclostrobin, and boscalid to Eastern honeybee Apis cerana cerena was first evaluated, and the chronic effects on multiple aspects were investigated after exposure to a one-tenth medium lethal dose (LD50) for 10 days. This study revealed that the LD50 values of azoxystrobin, pyraclostrobin and boscalid for adult Eastern honeybees were 12.7 μg/bee, 36.6 μg/bee, and >119 μg/bee, respectively. Midgut epithelial cells revealed that fungicide exposure caused increased intercellular spaces and varying degrees of vacuolization. Exposure to these three fungicides and their binary mixtures significantly affected glycerophospholipid, alanine, aspartate, and glutamate metabolism in Eastern honeybee midguts. Additionally, the relative composition of Lactobacillus, the dominant functional genus in Eastern honeybee guts decreased and microbial balance was disrupted. All fungicides and their mixtures induced strong transcriptional upregulation of genes associated with the immune response and encoding enzymes related to oxidative phosphorylation and metabolism, including abaecin, apidaecin, hymenotaecin, cyp4c3, cyp6a2 and hbg3. Our study provides important insight for understanding the effects of commonly used fungicides on nontarget pollinator and contributes to a more comprehensive assessment of fungicide effects on ecological and environmental safety.

Eastern honeybee Apis cerana sense cold flowering plants by increasing the static binding affinity of odorant-binding protein to cold floral volatiles from loquats

Eastern honeybee Apis cerana has important ecological value for the cold flowering loquat flower pollination in early winter in East Asia. However, the low-temperature adaptive pollination mechanism has not yet been revealed. One odorant-binding protein, OBP2, had been found that could bind to some plant volatiles with strong affinity before. In this study, by using competitive fluorescence binding assay, we first measured the ligand-binding profiles of recombinant OBP2 protein with nine representative aroma chemical substances from loquat flowers. Thermodynamic results showed that three loquat volatiles, 4-Methoxybenzaldehyde, (E)-Ethyl cinnamate, and Methyl cinnamate, have the strongest binding affinity with OBP2 with the static process. And interestingly their binding affinity significantly increased at low temperature (285 K/12 °C) compared to high temperature (298 K/25 °C). In addition, site-directed mutagenesis results showed that Met55 and Lys51 may be the key amino acid sites in the electrostatic and hydrophobic interactions of OBP2 interacting with Methyl cinnamate, respectively. This study suggests that OBP2 is functionally similar and universal in binding to different flower volatiles at low temperatures. Our studies interpreted a novel olfactory mechanism of A. cerana sensing loquat floral volatiles in cold early winter, and enrich a theoretical molecular basis for the temperature-adaptive ecological mechanism of insects' pollination.

Sex-Biased Expression of Olfaction-Related Genes in the Antennae of Apis cerana (Hymenoptera: Apidae).

The olfactory system is essential for honeybees to adapt to complex and ever-changing environments and maintain cohesiveness. The Eastern honeybee Apis cerana is native to Asia and has a long history of managed beekeeping in China. In this study, we analysed the antennal transcriptomes of A. cerana workers and drones using Illumina sequencing. A total of 5262 differentially expressed genes (DEGs) (fold change > 2) were identified between these two castes, with 2359 upregulated and 2903 downregulated in drones compared with workers. We identified 242 candidate olfaction-related genes, including 15 odourant-binding proteins (OBPs), 5 chemosensory proteins (CSPs), 110 odourant receptors (ORs), 9 gustatory receptors (GRs), 8 ionotropic receptors (IRs), 2 sensory neuron membrane proteins (SNMPs) and 93 putative odourant-degrading enzymes (ODEs). More olfaction-related genes have worker-biased expression than drone-biased expression, with 26 genes being highly expressed in workers’ antennae and only 8 genes being highly expressed in drones’ antennae (FPKM > 30). Using real-time quantitative PCR (RT-qPCR), we verified the reliability of differential genes inferred by transcriptomics and compared the expression profiles of 6 ORs (AcOR10, AcOR11, AcOR13, AcOR18, AcOR79 and AcOR170) between workers and drones. These ORs were expressed at significantly higher levels in the antennae than in other tissues (p < 0.01). There were clear variations in the expression levels of all 6 ORs between differently aged workers and drones. The relative expression levels of AcOR10, AcOR11, AcOR13, AcOR18 and AcOR79 reached a high peak in 15-day-old drones. These results will contribute to future research on the olfaction mechanism of A. cerana and will help to better reveal the odourant reception variations between different biological castes of honeybees.

Characterization of HSP70 expression in drones of Apis cerana (Hymenoptera: Apidae)

• The full-length HSP70 gene of the Eastern honeybee Apis cerana was cloned. • The expression patterns of the HSP70 gene in drones at different developmental stages and ages were investigated. • The expression levels of the HSP70 gene in drones at different reproductive statuses were analyzed. Heat shock proteins (HSPs) constitute a superfamily of molecular chaperones that are rapidly biosynthesized in response to various biotic and abiotic factors. In this study, we first cloned the full-length HSP70 gene of the Eastern honeybee Apis cerana . Then, using real-time quantitative PCR, we explored HSP70 expression profiles in drones at different developmental stages, ages, and reproductive statuses (with and without semen). The full-length HSP70 cDNA is 2421 bp, including a 1953-bp open reading frame (ORF) that encodes a polypeptide of 650 amino acids. The HSP70 gene consists of one intron and two exons. The phylogenetic analysis revealed that the HSP70 genes of A. cerana and Apis mellifera are the most closely related. We observed HSP70 expression at all selected developmental stages and detected the highest expression in pupae with an unpigmented body cuticle and brown eyes (Pb) and much lower expression in larvae hatched within 72 h. In adult drones of different ages, the highest expression level of HSP70 was observed in 16-day-old drones; significantly lower accumulation of HSP70 mRNA was detected in 4-day-old drones. There was no significant difference in HSP70 expression between drones with and without semen captured at the entrance, while the HSP70 gene expression level strikingly differed between drones captured at the entrance and the drones collected within the hive. Our study suggests that HSP70 might play a critical role in drone development and during reproductive mating events.

Genetic divergence and functional convergence of gut bacteria between the Eastern honey bee Apis cerana and the Western honey bee Apis mellifera

IntroductionThe functional relevance of intra-species diversity in natural microbial communities remains largely unexplored. The guts of two closely related honey bee species, Apis cerana and A. mellifera, are colonised by a similar set of core bacterial species composed of host-specific strains, thereby providing a good model for an intra-species diversity study. ObjectivesWe aim to assess the functional relevance of intra-species diversity of A. cerana and A. mellifera gut microbiota. MethodsHoney bee workers were collected from four regions of China. Their gut microbiomes were investigated by shotgun metagenomic sequencing, and the bacterial compositions were compared at the species level. A cross-species colonisation assay was conducted, with the gut metabolomes being characterised by LC-MS/MS. ResultsComparative analysis showed that the strain composition of the core bacterial species was host-specific. These core bacterial species presented distinctive functional profiles between the hosts. However, the overall functional profiles of the A. cerana and A. mellifera gut microbiomes were similar; this was further supported by the consistency of the honey bees’ gut metabolome, as the gut microbiota of different honey bee species showed rather similar metabolic profiles in the cross-species colonisation assay. Moreover, this experiment also demonstrated that the gut microbiota of A. cerana and A. mellifera could cross colonise between the two honey bee species. ConclusionOur findings revealed functional differences in most core gut bacteria between the guts of A. cerana and A. mellifera, which may be associated with their inter-species diversity. However, the functional profiles of the overall gut microbiomes between the two honey bee species converge, probably as a result of the overlapping ecological niches of the two species. Our findings provide critical insights into the evolution and functional roles of the mutualistic microbiota of honey bees and reveal that functional redundancy could stabilise the gene content diversity at the strain-level within the gut community.

Complete mitochondrial DNA sequence of the parasitic honey bee mite Varroa destructor (Mesostigmata: Varroidae)

Varroa destructor is a parasite mite of the eastern honey bee Apis cerana, which is native to Asia. The European honey bee Apis mellifera was imported to Asia from Europe and the USA for apiculture in the 19th century. In a short period of time, V. destructor parasitized the artificially introduced honey bees. Varroa destructor was estimated to have spread around the world with A. mellifera when it was exported from Asia to locations worldwide about 50 years ago. The mitochondrial DNA of the parasitic honey bee mite V. destructor was analyzed using next-generation sequencing. The complete mitochondrial genome of V. destructor was identified as a 16,476-bp circular molecule containing 13 protein-coding genes (PCGs), 22 tRNA genes, two rRNA genes, and one AT-rich control region. The heavy strand was predicted to have nine PCGs and 13 tRNA genes, whereas the light strand was predicted to contain four PCGs, nine tRNA genes, and two rRNA genes. All PCGs began with ATA as the start codon, except COIII and CytB, which had ATG as the start codon. Stop codons were of two types: TAA for eight genes and TAG for five genes. Molecular phylogenetic analysis revealed that V. destructor from Japan was genetically distant from that of France. A high base substitution rate of 2.82% was also confirmed between the complete mitochondrial DNA sequences of V. destructor from Japan and the USA, suggesting that one Varroa mite strain found in the USA is not from Japan.

New Viruses from the Ectoparasite Mite Varroa destructor Infesting Apis mellifera and Apis cerana.

Varroa destructor is an ectoparasitic mite of Asian or Eastern honeybees Apis cerana (A. cerana) which has become a serious threat to European subspecies of Western honeybees Apis mellifera (A. mellifera) within the last century. V. destructor and its vectored honeybee viruses became serious threats for colony survival. This is a short period for pathogen- and host-populations to adapt. To look for possible variation in the composition of viral populations we performed RNA metagenomic analysis of the Western honeybee subspecies A. m. ligustica, A. m. syriaca, A. m. intermissa, and A. cerana and their respective V. destructor mites. The analysis revealed two novel viruses: Varroa orthomyxovirus-1 (VOV-1) in A. mellifera and V. destructor and a Hubei like-virga virus-14 homolog in V. destructor. VOV-1 was more prevalent in V. destructor than in A. mellifera and we found evidence for viral replication in both hosts. Interestingly, we found differences in viral loads of A. cerana and their V. destructor, A. m. intermissa, and its V. destructor showed partial similarity, while A. m. ligustica and A. m. syriaca and their varroa where very similar. Deformed wing virus exhibited 82.20%, 99.20%, 97.90%, and 0.76% of total viral reads in A. m. ligustica, A. m. syriaca, A. m. intermissa, and A. cerana, respectively. This is the first report of a complete segmented-single-stranded negative-sense RNA virus genome in honeybees and V. destructor mites.

Ectoparasitic Mites Varroa underwoodi (Acarina: Varroidae) in Eastern Honeybees, but not in Western Honeybees.

The ectoparasitic mite Varroa destructor Anderson and Trueman (Acarina: Varroidae) shifted host from Eastern honeybees Apis cerana Fabricius (Hymenoptera: Apidae) to Western honeybees Apis mellifera Linnaeus (Hymenoptera: Apidae) with disastrous consequences globally. The high genetic diversity of V. destructor and abundant opportunities for cross-species transmission probably promoted this host shift. Whether Varroa underwoodi (Acarina: Varroidae) also exhibits these traits is unknown. Here, we conduct a large-scale survey across China on the occurrence, morphology, reproduction, and genetics of V. underwoodi in A. cerana and A. mellifera colonies to fill gaps in our knowledge of this mite and to determine whether host shifts occurred. Despite the large number of colonies screened, V. underwoodi was exclusively found in A. cerana, where it occurred at low infestation rates. Three genetic clades were detected in the V. underwoodi population, which differed neither in morphology nor in reproductive ability. Nevertheless, the genetic diversity of V. underwoodi is likely to increase chances for host shifts, even though opportunities for cross-species transmission seem low. More studies of the neglected Varroa species seem appropriate to enable a better understanding of host shifts in the Apis spp./Varroa spp. system and evaluate the potential risk they pose to apiculture with A. mellifera.

Discrimination of the entomological origin of honey according to the secretions of the bee (Apis cerana or Apis mellifera)

The eastern honeybee Apis cerana and the western honeybee Apis mellifera are the two most economically valuable honeybee species used in apiculture. In market, the price of Apis cerana honey (ACH) is usually several times higher than that of Apis mellifera honey (AMH) due to the production limit, resulting in wide adulteration and counterfeiting of ACH by AMH. In the present study, we compared honeybee secretions in these two kinds of honey, and found significant differences in protein profiles and hydrocarbon components. The SDS-PAGE pattern showed three species-specific bands with molecular weights between 15.0 and 29.4 KDa in ACH, and six species-specific bands in AMH with molecular weights between 13.8 and 33.1 KDa. The GC–MS-MS detection of the petroleum ether extracts of the two kinds of honey showed that 17-Pentatriacontene and Hentriacontane were the characteristic constituents of ACH and AMH, respectively. These two methods constitute a system to satisfy different needs for entomological authentication of honey samples.

Norwegian honey bees surviving Varroa destructor mite infestations by means of natural selection.

BackgroundManaged, feral and wild populations of European honey bee subspecies, Apis mellifera, are currently facing severe colony losses globally. There is consensus that the ectoparasitic mite Varroa destructor, that switched hosts from the Eastern honey bee Apis cerana to the Western honey bee A. mellifera, is a key factor driving these losses. For >20 years, breeding efforts have not produced European honey bee colonies that can survive infestations without the need for mite control. However, at least three populations of European honey bees have developed this ability by means of natural selection and have been surviving for >10 years without mite treatments. Reduced mite reproductive success has been suggested as a key factor explaining this natural survival. Here, we report a managed A. mellifera population in Norway, that has been naturally surviving consistent V. destructor infestations for >17 years.MethodsSurviving colonies and local susceptible controls were evaluated for mite infestation levels, mite reproductive success and two potential mechanisms explaining colony survival: grooming of adult worker bees and Varroa Sensitive Hygiene (VSH): adult workers specifically detecting and removing mite-infested brood.ResultsMite infestation levels were significantly lower in surviving colonies and mite reproductive success was reduced by 30% when compared to the controls. No significant differences were found between surviving and control colonies for either grooming or VSH.DiscussionOur data confirm that reduced mite reproductive success seems to be a key factor for natural survival of infested A. mellifera colonies. However, neither grooming nor VSH seem to explain colony survival. Instead, other behaviors of the adult bees seem to be sufficient to hinder mite reproductive success, because brood for this experiment was taken from susceptible donor colonies only. To mitigate the global impact of V. destructor, we suggest learning more from nature, i.e., identifying the obviously efficient mechanisms favored by natural selection.

Brain metabolomic profiling of eastern honey bee (Apis cerana) infested with the mite Varroa destructor

The mite Varroa destructor is currently the greatest threat to apiculture as it is causing a global decrease in honey bee colonies. However, it rarely causes serious damage to its native hosts, the eastern honey bees Apis cerana. To better understand the mechanism of resistance of A. cerana against the V. destructor mite, we profiled the metabolic changes that occur in the honey bee brain during V. destructor infestation. Brain samples were collected from infested and control honey bees and then measured using an untargeted liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based global metabolomics method, in which 7918 and 7462 ions in ESI+ and ESI- mode, respectively, were successfully identified. Multivariate statistical analyses were applied, and 64 dysregulated metabolites, including fatty acids, amino acids, carboxylic acid, and phospholipids, amongst others, were identified. Pathway analysis further revealed that linoleic acid metabolism; propanoate metabolism; and glycine, serine, and threonine metabolism were acutely perturbed. The data obtained in this study offer insight into the defense mechanisms of A. cerana against V. destructor mites and provide a better method for understanding the synergistic effects of parasitism on honey bee colonies.

No evidence of queen thelytoky following interspecific crosses of the honey bees Apis cerana and Apis mellifera

The human-mediated dispersal of species over geographical boundaries can bring previously isolated sister taxa into contact. Interspecific mating between closely related species may then occur, with various outcomes ranging from hybridization to reproductive interference. In the case of the Eastern honey bee Apis cerana and the Western honey bee Apis mellifera, an additional possible reproductive outcome has been posited: interspecific sperm triggers queens to produce daughters from unfertilized eggs via thelytokous parthenogenesis. Such an outcome would go unnoticed in natural population mergers, as queens, which are polyandrous, are likely to mate with both conspecific and interspecific males. We performed reciprocal crosses between A. mellifera and A. cerana via artificial insemination, plus control inseminations of saline (five queens per species per treatment), and genetically assessed the sex and origin of any resulting offspring. Neither A. cerana nor A. mellifera queens produced viable female brood after receiving interspecific semen, indicating a high cost of interspecific mating for both species. In two A. cerana colonies headed by cross-inseminated queens, workers responded by activating ovaries and laying eggs that were mainly male but occasionally female (i.e. thelytokous, 2% of brood), despite the queen’s continued presence in the nest. We conclude that thelytoky is not a consistent response to interspecific mating by queens of A. mellifera or A. cerana. Rather, at least in A. cerana, when colonies are faced with “mis-mated” queens, it may be up to the workers to secure the reproductive future of the colony.

Efficacy of silver ions against Sacbrood virus infection in the Eastern honey bee Apis cerana.

Although silver is known to be a broad-spectrum biocidal agent, the effects of this metal against Sacbrood virus have not yet been investigated. In this study, we evaluated the efficacy of silver ions against natural Korean sacbrood virus (KSBV) infection of Apis (A.) cerana. Ten KSBV-infected colonies containing A. cerana with similar strength and activity were selected from an apiary located in Bosung-gun (Korea). Among these, five colonies were randomly assigned to the treatment group that was fed sugar syrup containing 0.2 mg/L silver ions. The other colonies were assigned to the untreated control group in which bees were given syrup without the silver ions. To assess the efficacy of the silver ions, colony strength, colony activity, and the number of dead larvae per hive were measured. During the experimental period, the test group maintained its strength and activity until day 32 while those of bees in the control group decreased sharply after day 8 to 16. Survival duration of the test group was significantly longer (40 days) than that of the control group (21 days). These results strongly indicated that silver ions are effective against KSBV infection in A. cerana.

Genetic reincarnation of workers as queens in the Eastern honeybee Apis cerana.

Thelytokous parthenogenesis, or the asexual production of female offspring, is rare in the animal kingdom, but relatively common in social Hymenoptera. However, in honeybees, it is only known to be ubiquitous in one subspecies of Apis mellifera, the Cape honeybee, A. mellifera capensis. Here we report the appearance of queen cells in two colonies of the Eastern honeybee Apis cerana that no longer contained a queen or queen-produced brood to rear queens from. A combination of microsatellite genotyping and the timing of the appearance of these individuals excluded the possibility that they had been laid by the original queen. Based on the genotypes of these individuals, thelytokous production by natal workers is the most parsimonious explanation for their existence. Thus, we present the first example of thelytoky in a honeybee outside A. mellifera. We discuss the evolutionary and ecological consequences of thelytoky in A. cerana, in particular the role thelytoky may play in the recent invasions by populations of this species.

Why acquiesce? Worker reproductive parasitism in the Eastern honeybee (Apis cerana).

Most societies are vulnerable to rogue individuals that pursue their own interests at the expense of the collective entity. Societies often protect themselves from selfish behaviour by 'policing', thereby enforcing the interests of the collective over those of individuals. In insect societies, for example, selfish workers can activate their ovaries and lay eggs, exploiting the collective brood rearing system for individual benefit. Policing, usually in the form of oophagy of worker-laid eggs, controls selfish behaviour. Importantly, once an effective system of policing has evolved, the incentive for personal reproduction is lost, and 'reproductive acquiescence' in which ovary activation is rare or absent is predicted to evolve. Studies of social Hymenoptera have largely supported the prediction of worker 'acquiescence'; workers of most species where policing is well developed have inactive ovaries. However, the eastern honeybee Apis cerana appears to be an exception. A.cerana colonies are characterized by highly efficient policing, yet about 5% of workers have active ovaries, even when a queen is present. This suggests that the evolution of acquiescence is incomplete in A.cerana. We regularly sampled male eggs and pupae from four A.cerana colonies. Workers had high levels of ovary activation overall (11.7%), and 3.8% of assignable male eggs and 1.1% of assignable male pupae were worker-laid. We conclude that workers with active ovaries lay their eggs, but these rarely survive to pupation because of intense policing. We then used our findings as well as previously published data on A.cerana and A.mellifera to redo the meta-analysis on which reproductive acquiescence theory is based. Including data on both species did not affect the relationship between effectiveness of policing and levels of worker reproduction. Their inclusion did, however, seriously weaken the relationship between relatedness among workers and levels of worker reproduction. Our work thus suggests that relatedness among workers does not affect the probability that workers will attempt to reproduce, but that it is coercion by peers that limits worker reproduction.

Effect of queen excluders on ovary activation in workers of the Eastern honeybee Apis cerana

Honeybee workers generally refrain from personal reproduction when a queen is present. Workers discern the presence and fecundity of the queen via volatile pheromones that permeate throughout the colony. Pheromones are emitted both by the queen herself and by the brood that she produces. If pheromone production is disrupted, some workers initiate egg laying. The Eastern honeybee Apis cerana is unusual in that workers have high levels of ovary activation even in the presence of a queen. To investigate the effect of disruption to pheromone dispersal, we fitted three A. cerana colonies with vertical queen excluders, thus splitting the colonies into a half containing a queen and a half without a queen. We regularly sampled adult workers from both sides of the excluder for 3 weeks. We also sampled workers from three control colonies that did not contain excluders. We found a significant increase in worker ovary activation 3 days after addition of excluders, suggesting that the reduced dispersal of pheromones allowed some workers to become reproductively active. Workers attempted to rear queen cells on the queenless halves of all three colonies. Queen-rearing ceased on day 9, at which time no queen-laid brood remained on the queenless halves of the colonies. Ovary activation rates continued to climb until day 9 and then gradually began to decline. With the exception of one egg, we did not observe worker-laid brood on the queenless side of the colonies, suggesting that workers continued policing eggs laid by workers. We conclude that if the distribution of brood pheromone is impeded, workers prepare to supersede their queen, accompanied by high levels of worker ovary activation. However, because workers continue to police each other, high ovary activation does not result in worker-produced drones.

High-throughput sequencing identification of genes involved with Varroa destructor resistance in the eastern honeybee, Apis cerana.

Varroa destructor is the greatest threat to the honeybee Apis mellifera worldwide, while it rarely causes serious harm to its native host, the Eastern honeybee Apis cerana. The genetic mechanisms underlying the resistance of A. cerana to Varroa remain unclear. Thus, understanding the molecular mechanism of resistance to Varroa may provide useful insights for reducing this disease in other organisms. In this study, the transcriptomes of two A. cerana colonies were sequenced using the Illumina Solexa sequencing method. One colony was highly affected by mites, whereas the other colony displayed strong resistance to V. destructor. We determined differences in gene expression in the two colonies after challenging the colonies with V. destructor. After de novo transcriptome assembly, we obtained 91,172 unigenes for A. cerana and found that 288 differentially expressed genes varied by more than 15-fold. A total of 277 unigenes were present at higher levels in the non-affected colony. Genes involved in resistance to Varroa included unigenes related to skeletal muscle movement, olfactory sensitivity, and transcription factors. This suggests that hygienic behavior and grooming behavior may play important roles in the resistance to Varroa.

A scientific note on Israeli acute paralysis virus infection of Eastern honeybee Apis cerana and vespine predator Vespa velutina

Financial support was provided to OY and PN by the COST funded project VIVA and to VD by the Qian-Tang River expert program.

Biology and control of Varroa destructor

The ectoparasitic honey bee mite Varroa destructor was originally confined to the Eastern honey bee Apis cerana. After a shift to the new host Apis mellifera during the first half of the last century, the parasite dispersed world wide and is currently considered the major threat for apiculture. The damage caused by Varroosis is thought to be a crucial driver for the periodical colony losses in Europe and the USA and regular Varroa treatments are essential in these countries. Therefore, Varroa research not only deals with a fascinating host–parasite relationship but also has a responsibility to find sustainable solutions for the beekeeping. This review provides a survey of the current knowledge in the main fields of Varroa research including the biology of the mite, damage to the host, host tolerance, tolerance breeding and Varroa treatment. We first present a general view on the functional morphology and on the biology of the Varroa mite with special emphasis on host–parasite interactions during reproduction of the female mite. The pathology section describes host damage at the individual and colony level including the problem of transmission of secondary infections by the mite. Knowledge of both the biology and the pathology of Varroa mites is essential for understanding possible tolerance mechanisms in the honey bee host. We comment on the few examples of natural tolerance in A. mellifera and evaluate recent approaches to the selection of Varroa tolerant honey bees. Finally, an extensive listing and critical evaluation of chemical and biological methods of Varroa treatments is given. This compilation of present-day knowledge on Varroa honey bee interactions emphasizes that we are still far from a solution for Varroa infestation and that, therefore, further research on mite biology, tolerance breeding, and Varroa treatment is urgently needed.

Inference on microsatellite mutation processes in the invasive mite, Varroa destructor, using reversible jump Markov chain Monte Carlo

Varroa destructor is a parasitic mite of the Eastern honeybee Apis cerana. Fifty years ago, two distinct evolutionary lineages (Korean and Japanese) invaded the Western honeybee Apis mellifera. This haplo–diploid parasite species reproduces mainly through brother–sister matings, a system which largely favors the fixation of new mutations. In a worldwide sample of 225 individuals from 21 locations collected on Western honeybees and analyzed at 19 microsatellite loci, a series of de novo mutations was observed. Using historical data concerning the invasion, this original biological system has been exploited to compare three mutation models with allele size constraints for microsatellite markers: stepwise (SMM) and generalized (GSM) mutation models, and a model with mutation rate increasing exponentially with microsatellite length (ESM). Posterior probabilities of the three models have been estimated for each locus individually using reversible jump Markov Chain Monte Carlo. The relative support of each model varies widely among loci, but the GSM is the only model that always receives at least 9% support, whatever the locus. The analysis also provides robust estimates of mutation parameters for each locus and of the divergence time of the two invasive lineages (67,000 generations with a 90% credibility interval of 35,000–174,000). With an average of 10 generations per year, this divergence time fits with the last post-glacial Korea–Japan land separation.