Honey bee genotypes and the environment

Although knowledge about honey bee geographic and genetic diversity has increased tremendously in recent decades (Meixner et al., 2013), the adaptation of honey bees to their local environment has not been well studied. The current demand for high economic performance of bee colonies with desirable behavioural characteristics contributes to changing the natural diversity via mass importations and an increasing practice of queen trade and colony movement. At the same time, there is also a growing movement in opposition to this trend, aimed at conserving the natural heritage of local populations, with on-going projects in several countries (Strange et al., 2008; Dall’Olio et al., 2008, De la Rúa et al., 2009)

A comparative study of colony performance, hygienic behaviour and parasite and disease infection in the endemic honeybee A. M. Ruttneri and the introduced A. M. Ligustica in Malta

Apis mellifera ruttneri, the honey bee subspecies endemic to Malta, must be regarded as seriously endangered. However, there is a critical need for scientific data to support and guide conservation measures, since only two scientific papers concerning this subspecies were published since its original description in 1997. To this end in June 2017, a first systematic study was initiated to compare colony development, performance, hygienic behaviour and infection levels of honey bee diseases of the endemic honey bee with introduced colonies of A. m. ligustica. A total of 33 colonies (A. m. ruttneri, n=15 and A. m. ligustica, n=18, headed by sister queens) were evenly distributed across two locations on Malta, at a central site UNI (n=17) and a site in the Southern region SIGG (n=16). After an initial treatment against Varroa destructor, no further chemical treatment was performed. Standard methods are used to assess colony productivity and behaviour (number of adult bees, number of brood cells, number of visible cells with pollen) in regular intervals. Hygienic behaviour is assessed using the pin test method; Varroa infestation is monitored using powdered-sugar and natural mite fall methods. Assessment of infection levels with Nosema spp. and the most common honey bee viruses is also being carried out. The selected commercial stocks of A. m. ligustica remain consistently less defensive and calmer on the combs. However, by spring 2018, the A. m. ruttneri colonies in general showed higher numbers of adult bees, brood cells and pollen cells. Early seasonal drone production and significant swarming behaviour were observed in the colonies of the endemic bee, but not in A. m. ligustica colonies. The baseline data on the performance of native and introduced genotypes under Maltese environmental conditions provided by this study will contribute to guiding beekeepers in their decision on queen purchases, and ultimately, support conservation measures for A. m. ruttneri.peer-reviewe

Evaluation of Suppressed Mite Reproduction (SMR) Reveals Potential for Varroa Resistance in European Honey Bees (Apis melliferaL.)

Simple Summary The miteVarroa destructorrepresents a great threat to honey bees and the beekeeping industry. The opportunity to select and breed honey bees that are naturally able to fight the mite stands a sustainable solution. This can be achieved by evaluation of the failure of mite reproduction (SMR, suppressed mite reproduction). We conducted a large European experiment to assess the SMR trait in different populations of honey bees spread over 13 different countries, and representing different honey bee populations. The first goal was to standardize and validate the SMR evaluation method, and then to compare the SMR trait between the different populations. Our results indicate that it is necessary to examine at least 35 brood cells infested by a single mite to reliably estimate the SMR score of any given colony. Several colonies from our dataset display high SMR scores, indicating that this trait is present within the European honey bee populations. No major differences could be identified between countries for a given population, or between populations in different countries. This study shows the potential to increase selection efforts to breedV. destructorhoney bee resistant populations. In the fight against theVarroa destructormite, selective breeding of honey bee (Apis melliferaL.) populations that are resistant to the parasitic mite stands as a sustainable solution. Selection initiatives indicate that using the suppressed mite reproduction (SMR) trait as a selection criterion is a suitable tool to breed such resistant bee populations. We conducted a large European experiment to evaluate the SMR trait in different populations of honey bees spread over 13 different countries, and representing different honey bee genotypes with their local mite parasites. The first goal was to standardize and validate the SMR evaluation method, and then to compare the SMR trait between the different populations. Simulation results indicate that it is necessary to examine at least 35 single-infested cells to reliably estimate the SMR score of any given colony. Several colonies from our dataset display high SMR scores indicating that this trait is present within the European honey bee populations. The trait is highly variable between colonies and some countries, but no major differences could be identified between countries for a given genotype, or between genotypes in different countries. This study shows the potential to increase selective breeding efforts ofV. destructorresistant populations

Authoritative subspecies diagnosis tool for European honey bees based on ancestryinformative SNPs

Background With numerous endemic subspecies representing four of its five evolutionary lineages, Europe holds a large fraction of Apis mellifera genetic diversity. This diversity and the natural distribution range have been altered by anthropogenic factors. The conservation of this natural heritage relies on the availability of accurate tools for subspecies diagnosis. Based on pool-sequence data from 2145 worker bees representing 22 populations sampled across Europe, we employed two highly discriminative approaches (PCA and F-ST) to select the most informative SNPs for ancestry inference. Results Using a supervised machine learning (ML) approach and a set of 3896 genotyped individuals, we could show that the 4094 selected single nucleotide polymorphisms (SNPs) provide an accurate prediction of ancestry inference in European honey bees. The best ML model was Linear Support Vector Classifier (Linear SVC) which correctly assigned most individuals to one of the 14 subspecies or different genetic origins with a mean accuracy of 96.2% +/- 0.8 SD. A total of 3.8% of test individuals were misclassified, most probably due to limited differentiation between the subspecies caused by close geographical proximity, or human interference of genetic integrity of reference subspecies, or a combination thereof. Conclusions The diagnostic tool presented here will contribute to a sustainable conservation and support breeding activities in order to preserve the genetic heritage of European honey bees.The SmartBees project was funded by the European Commission under its FP7 KBBE programme (2013.1.3-02, SmartBees Grant Agreement number 613960) https://ec.europa.eu/research/fp7.MP was supported by a Basque Government grant (IT1233-19). The funders provided the financial support to the research, but had no role in the design of the study, analysis, interpretations of data and in writing the manuscript

A pan-European epidemiological study reveals honey bee colony survival depends on beekeeper education and disease control

Reports of honey bee population decline has spurred many national efforts to understand the extent of the problem and to identify causative or associated factors. However, our collective understanding of the factors has been hampered by a lack of joined up trans-national effort. Moreover, the impacts of beekeeper knowledge and beekeeping management practices have often been overlooked, despite honey bees being a managed pollinator. Here, we established a standardised active monitoring network for 5 798 apiaries over two consecutive years to quantify honey bee colony mortality across 17 European countries. Our data demonstrate that overwinter losses ranged between 2% and 32%, and that high summer losses were likely to follow high winter losses. Multivariate Poisson regression models revealed that hobbyist beekeepers with small apiaries and little experience in beekeeping had double the winter mortality rate when compared to professional beekeepers. Furthermore, honey bees kept by professional beekeepers never showed signs of disease, unlike apiaries from hobbyist beekeepers that had symptoms of bacterial infection and heavy Varroa infestation. Our data highlight beekeeper background and apicultural practices as major drivers of honey bee colony losses. The benefits of conducting trans-national monitoring schemes and improving beekeeper training are discussed

Apis mellifera pomonella, a new honey bee subspecies from Central Asia

Endemic honey bees of the Tien Shan Mountains in Central Asia are described as a new subspecies, Apis mellifera pomonella, on the basis of morphometric analyses. Principal component and discriminant analysis of the morphological characters measured clearly place these bees into the oriental evolutionary branch of honey bees, but also show that they are distinct from the other subspecies in this lineage. The existence of this newly described honey bee subspecies extends the range of endemic A. mellifera more than 2000 km eastward than previously estimated. Sequence analysis of mitochondrial DNA places A. m. pomonella within the C mitochondrial lineage (a group that is inclusive of both C and O morphological lineages). These findings support the conclusion that A. m. pomonella has a phylogeographic history shared with subspecies from the eastern limit of the previously known range

A current perspective on honey bee health

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Mitochondrial DNA polymorphisms in honey bee subspecies from Kenya

Thirty-nine samples of Apis mellifera monticola and A. m. scutellata from three different regions of Kenya were analyzed for mitochondrial DNA (mtDNA) variation using 6-base and 4-base restriction enzymes. Restriction with HpaII and AluI resulted in distinct patterns that together produced three different haplotypes. While haplotypes 2 and 3 were restricted to samples from the mountain forest, haplotype 1 was found in A. m. scutellata and in all samples from the Ngong Hills. No introgression of A. m. scutellata mtDNA was detected in bees collected in mountain environments, but a few samples from the savanna had A. m. monticola morphology, or mtDNA, or both. These results support the hypothesis that A. m. monticola is a distinct subspecies and not an ecotype of A. m. scutellata. The polymorphic restriction sites were mapped. Ten samples of A. m. litorea from the coast of Kenya were analyzed using polymerase chain reaction (PCR) amplification and subsequent restriction analysis. All samples of A. m. litorea shared the A. m. scutellata haplotype.Polymorphisme de l'ADNmt chez les sous-espèces d'abeilles domestiques du Kenya. La variabilité de l'ADNmt a été étudiée sur 39 échantillons d'Apis mellifera monticola et d'A. m. scutellata identifiés morphologiquement et provenant de trois régions montagneuses du Kenya et des savanes adjacentes. L'ADN total a été digéré par les enzymes AccI, AluI, BclI, BglII, EcoRI, HpaII, MboI, RsaI et XbaI, reconnaissant des sites de restriction à quatre ou six bases. Les fragments ont été séparés par électrophorèse sur gel d'agarose à 1,2 % , colorés au bromure d'éthidium, photographiés et transférés sur des membranes de nitrocellulose. Ensuite, les membranes ont été préhybridées et hybridées à 50 $^{\circ}$C avec une sonde d'ADN radiomarquée produite à partir d'ADNmt purifié d'abeilles. Les sites de restrictions polymorphes ont été cartographiés en effectuant des digestions doubles avec EcoRV, XhoI et AccI. D'autre part, le polymorphisme de restriction de dix échantillons d'A. m. litorea récoltés sur la côte du Kenya a été analysé à l'aide d'amplification par PCR suivie de digestions de restriction. Tous les échantillons de l'étude avaient en commun les profils de restriction produits par les enzymes AccI, BclI, BglII, EcoRI, RsaI et XbaI. La restriction avec les enzymes à quatre bases, AluI, HpaII, a permis de mettre en évidence au sein des deux races monticola et scutellata (Fig. 1) trois haplotypes différents (Tab. I), qui présentent une répartition géographique caractéristique (Fig. 2). La figure 3 montre les positions des sites de restriction polymorphes cartographiés pour AluI et HpaII. Tandis que les haplotypes 2 et 3 sont limités aux échantillons de A. m. monticola du Mont Elgon et du Mont Kenya, l'haplotype 1 se trouve chez A. m. scutellata et dans tous les échantillons des Ngong Hills, région sujette à une urbanisation croissante. C'est la première fois que l'on met en évidence des différences diagnostiques dans la variation des profils d'ADNmt parmi les races d'abeilles mellifères d'Afrique orientale. Nos résultats prouvent clairement la validité de l'hypothèse selon laquelle A. m. monticola ne peut être considérée comme l'écotype d'A. m. scutellata, mais est le résultat de sa propre histoire évolutive. à la lumière des changements climatiques survenus pendant et après le Pléistocène, les populations actuellement disjointes d'A. m. monticola représentent les reliques d'une plus grande population d'abeilles du Pléistocène actuellement limitées à des zones refuges dans les montagnes. Nous n'avons pas détecté d'introgression chez A. m. scutellata parmi les échantillons récoltés dans les régions montagneuses au travers des études de la morphologie et de la variation de l'ADNmt. Ceci est en contradiction avec l'hypothèse des migrations verticales à grande échelle d'A. m. scutellata depuis les savanes vers les montagnes. Au contraire, quelques colonies prélevées dans la savane soit avaient la morphologie et l'ADNmt d'A. m. monticola, soit combinaient la morphologie d'une sous-espèce avec l'ADNmt de l'autre (Fig. 2). Alors que les populations d'abeilles voisines du Mont Elgon et celles voisines du Mont Kenya présentaient des différences prononcées, les abeilles des Ngong Hills n'avaient qu'un seul haplotype typique d' A.m. scutellata. Nous émettons l'hypothèse que ceci est le résultat d'une hybridation entre les abeilles de montagne et celles de savane, conséquence d'une déforestation et d'une urbanisation grandissantes de cette région. Tous les échantillons d'A. m. litorea de cette étude partageaient l'haplotype d'ADNmt typique d' A. m. scutellata. Ce résultat ne fournit pas de nouvel élément de réponse à la question : A. m. litorea doit elle être considérée comme un écotype d' A. m. scutellata ou comme une sous-espèce distincte, comme le suggère l'analyse morphométrique

Genetic characterization of honey bee (Apis mellifera cypria) populations in northern Cyprus

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