Spatial foraging patterns of the African honey bee,Apis mellifera scutellata

Recruitment patterns were investigated for the African honey bee in the Okavango River Delta, Botswana. The waggle dances of two observation colonies maintained in the field were monitored and used to construct maps of daily recruitment activity. These maps revealed that the African colonies frequently adjusted the allocation of recruits among food patches, recruited for 16–17 different food sites/day over areas of 55–80 km ² ,and concentrated the majority of recruitment within 1 km of the hives (median foraging distances for the two colonies were 295 and 563 m). In both colonies pollen foragers were more abundant than nectar foragers, and pollen sources indicated by waggle dancers were significantly closer to the hives than nectar sources. Compared to the recruitment patterns of temperate climate colonies, the African colonies had smaller recruitment areas, smaller mean recruitment distances, and a greater emphasis on pollen foraging. These differences may be related to the contrasting survival strategies followed by tropical-versus temperate-climate honey bees.     

Hygienic behavior of the honey bee (Apis mellifera) is independent of sucrose responsiveness and foraging ontogeny

Hygienic behavior in honey bees is a behavioral mechanism of disease resistance. Bees bred for hygienic behavior exhibit an increased olfactory sensitivity to odors of diseased brood, which is most likely differentially enhanced in the hygienic line by the modulatory effects of octopamine (OA), a noradrenaline-like neuromodulator. Here, we addressed whether the hygienic behavioral state is linked to other behavioral activities known to be modulated by OA. We specifically asked if, during learning trials, bees from hygienic colonies discriminate better between odors of diseased and healthy brood because of differences in sucrose (reward) response thresholds. This determination had to be tested because sucrose response thresholds are susceptible to OA modulation and may have influenced the honey bee's association of the conditioned stimulus (odor) with the unconditioned stimulus (i.e., the sucrose reward). Because the onset of first foraging is also modulated by OA, we also examined whether bees from hygienic colonies differentially forage at an earlier age compared to bees from non-hygienic colonies. Our study revealed that 1-day- and 15- to 20-day-old bees from the hygienic line do not have lower sucrose response thresholds compared to bees from the non-hygienic lines. In addition, hygienic bees did not forage at an earlier age or forage preferentially for pollen as compared to non-hygienic bees. These results support the idea that OA does not function in honey bees simply to enhance the detection of all chemical cues non-selectively or control related behaviors regardless of their environmental milieu. Our results indicate that the behavioral profile of the hygienic bee is sculpted by multiple factors including genetic, neural, social and environmental systems.     

Transcriptional response to foraging experience in the honey bee mushroom bodies

Enriched environmental conditions induce neuroanatomical plasticity in a variety of vertebrate and invertebrate species. We explored the molecular processes associated with experience-induced plasticity, using naturally occurring foraging behavior in adult worker honey bees (Apis mellifera). In honey bees, the mushroom bodies exhibit neuroanatomical plasticity that is dependent on accumulated foraging experience. To investigate molecular processes associated with foraging experience, we performed a time-course microarray study to examine gene expression changes in the mushroom bodies as a function of days foraged. We found almost 500 genes that were regulated by duration of foraging experience. Bioinformatic analyses of these genes suggest that foraging experience is associated with multiple molecular processes in the mushroom bodies, including some that may contribute directly to neuropil growth, and others that could potentially protect the brain from the effects of aging and physiological stress.     

PKA and PKC content in the honey bee central brain differs in genotypic strains with distinct foraging behavior

Selection of honey bees for pollen storage resulted in high and low pollen-hoarding strains differing in foraging behavior traits including resource choice and quality, load size, sucrose responsiveness, age of foraging initiation, and learning performance. To determine how these genotypic differences correlate with changes at the level of proteins involved in neuronal function, we measured the content of protein kinase A, protein kinase C, and synapsin in the brains of high- and low-strain bees. In the central brain protein kinase A and protein kinase C levels were greater in high-strain bees and increased from emergence to 5 days in both strains. By 15 days, high-strain bees retained significantly higher levels of protein kinase C than low-strain bees, but overall protein kinase C content decreased in both strains. Synapsin levels increased from emergence to 5 days but did not differ between the two strains. In contrast to the protein kinase A content in the central brain, the basal protein kinase A activity did not differ between the strains or between the two age groups. This provides first evidence that the two genetic strains of honey bees show characteristic differences in the regulation of protein expression that may contribute to the behavioral differences between them.Abbreviations PKA protein kinase A - PKC protein kinase C     

A flexible model of foraging by a honey bee colony: the effects of individual behaviour on foraging success

This paper develops and explores a model of foraging in honey bee colonies. The model may be applied to forage sources with various properties, and to colonies with different foraging-related parameters. In particular, we examine the effect of five foraging-related parameters on the foraging response and consequent nectar intake of a homogeneous colony. The parameters investigated affect different quantities critical to the foraging cycle--visit rate (affected by g), probability of dancing (mpd and bpd), duration of dancing (mcirc), or probability of abandonment (A). We show that one parameter, A, affects nectar intake in a nonlinear way. Further, we show that colonies with a midrange value of any foraging parameter perform better than the average of colonies with high- and low-range values, when profitable sources are available. Together these observations suggest that a heterogeneous colony, in which a range of parameter values are present, may perform better than a homogeneous colony. We modify the model to represent heterogeneous colonies and use it to show that the most important effect of heterogeneous foraging behaviour within the colony is to reduce the variance in the average quantity of nectar collected by heterogeneous colonies.     

Effects of selection for honey bee worker reproduction on foraging traits

The “reproductive ground plan” hypothesis (RGPH) proposes that reproductive division of labour in social insects had its antecedents in the ancient gene regulatory networks that evolved to regulate the foraging and reproductive phases of their solitary ancestors. Thus, queens express traits that are characteristic of the reproductive phase of solitary insects, whereas workers express traits characteristic of the foraging phase. The RGPH has also been extended to help understand the regulation of age polyethism within the worker caste and more recently to explain differences in the foraging specialisations of individual honey bee workers. Foragers that specialise in collecting proteinaceous pollen are hypothesised to have higher reproductive potential than individuals that preferentially forage for nectar because genes that were ancestrally associated with the reproductive phase are active. We investigated the links between honey bee worker foraging behaviour and reproductive traits by comparing the foraging preferences of a line of workers that has been selected for high rates of worker reproduction with the preferences of wild-type bees. We show that while selection for reproductive behaviour in workers has not altered foraging preferences, the age at onset of foraging of our selected line has been increased. Our findings therefore support the hypothesis that age polyethism is related to the reproductive ground plan, but they cast doubt on recent suggestions that foraging preferences and reproductive traits are pleiotropically linked.     

Spatial foraging patterns and colony energy status in the African honey bee,Apis mellifera scutellata

The relationship between changes in foraging patterns (inferred from waggle dance activity) and colony energy status (inferred from brood rearing activity, food storage, and colony weight) was examined for the African honey bee during a period of relative resource abundance and resource dearth. When resources were more abundant mean foraging distances (about 400 m) and foraging areas (4–5 km²) were small, and colonies recruited to 12–19 different sites per day. Colony foraging ranges and sites visited increased slightly during the dearth period, yet foraging continued to be concentrated within less than 10 km². The degree to which fluctuations in foraging patterns were correlated with colony energy status varied with the availability of floral resources. During periods of relative forage abundance, increases in foraging range and number of sites visited were significantly correlated with increases in brood rearing and colony weight. In contrast, colonies examined during periods of resource dearth exhibited no correlations between foraging areas, foraging distances, and fluctuations in brood rearing, food storage, or colony weight. Thus, during dearth periods colonies may not be able to coordinate foraging patterns with changes in colony energy status.     

Influence of visual targets and landmarks on honey bee foraging and waggle dancing

Animals use diverse sensory stimuli to navigate their environment and to recognize rewarding food sources.Honey bees use visual atributes of the targeted food source,such as its color,shape,size,direction and distance from the hive,and the landmarks around it to navigate during foraging.They transmit the location information of the food source to other bees if it is highly rewarding.To investigate the relative importance of these attributes,we trained bees to feeders in two different experiments.In the first experiment,we asked whether bees prefer to land on(a)a similar feeder at a different distance on the same heading or on(b)a visually distinct feeder located at the exact same location.We found that,within a short foraging range,bees relied heavily on the color and the shape of the food source and to a lesser extent on its distance from the hive.In the second experiment,we asked if moving the main landmark or the feeder(visual target)influenced recruitment dancing for the feeder.We found that foragers took longer to land and danced fewer circuits when the location of the food source,or a major landmark associated with it,changed.These results demonstrate that prominent visual atributes of food sources and landmarks are evidently more reliable than distance information and that foraging bees heavily utilize these visual cues at the later stages of their journey.     

Influence of honey bee, Apis mellifera, hives and field size on foraging activity of native bee species in pumpkin fields

The purpose of this study was to identify bee species active in pumpkin fields in New York and to estimate their potential as pollinators by examining their foraging activity. In addition, we examined whether foraging activity was affected by either the addition of hives of the honey bee, Apis mellifera L., or by field size. Thirty-five pumpkin (Cucurbita spp.) fields ranging from 0.6 to 26.3 ha, 12 supplemented with A. mellifera hives and 23 not supplemented, were sampled during peak flowering over three successive weeks in 2008 and 2009. Flowers from 300 plants per field were visually sampled for bees on each sampling date. A. mellifera, Bombus impatiens Cresson, and Peponapis pruinosa (Say) accounted for 99% of all bee visits to flowers. A. mellifera and B. impatiens visited significantly more pistillate flowers than would be expected by chance, whereas P. pruinosa showed no preference for visiting pistillate flowers. There were significantly more A. mellifera visits per flower in fields supplemented with A. mellifera hives than in fields not supplemented, but there were significantly fewer P. pruinosa visits in supplemented fields. The number of B. impatiens visits was not affected by supplementation, but was affected by number of flowers per field. A. mellifera and P. pruinosa visits were not affected by field size, but B. impatiens visited fewer flowers as field size increased in fields that were not supplemented with A. mellifera hives. Declining A. mellifera populations may increase the relative importance of B. impatiens in pollinating pumpkins in New York.     

Methoprene does not affect food preferences and foraging performance in honey bee workers

The fundamental determinants of division of labor among honey bee workers are age, genotype, and environment. These determinants work through intermediate physiological channels to realize particular patterns of division of labor. The change of juvenile hormone (JH) titer in worker bees is one such channel. Previous studies concentrated on the impact of JH on timing of in-hive and foraging activity. Here we examined the effects of JH on task specialization and the collection of pollen or nectar by same-age bees and we tested the possible impact on JH titer on foraging performance. Methoprene treatments were conducted after workers began to forage inside a flight room. We found that methoprene, a JH analogue, had no effect on preferences for pollen or nectar and, also, did not influence nectar foraging rate, nectar load size, and foraging span.     

Seasonal patterns of foraging activity in colonies of the African honey bee,Apis mellifera scutellata,in Africa

Summary Seasonal foraging patterns were investigated using six observation colonies maintained in the Okavango Delta, Botswana. Pollen collection, flight from the hive, and recruitment for pollen and nectar sources occurred throughout the 11 months of the study. However, the distribution of foraging activity throughout the day changed seasonally. Colonies emphasized recruitment for pollen sites throughout most of the year. Brood production occurred in all months except May, and there was a significant, positive correlation between the proportion of recruitment activity devoted to pollen sources and the amount of brood comb in the colonies. The seasonal foraging patterns ofscutellata in the Okavango were similar to those of Africanized honey bees in the neotropics. The extended foraging season and emphasis on pollen collection may be associated with the high swarming rates and migrational movements of tropical honey bees.     

Environmental and genetic influences on flight metabolic rate in the honey bee,Apis mellifera

The four isoforms of the catalytic subunit of Na(+)/K(+)-ATPase identified in rats differ in their affinities for ions and ouabain. Moreover, its expression is tissue-specific, developmentally and hormonally regulated. The aim of the present work was to evaluate the influence of age on the ratio and density of these isoforms in crude membrane preparations from rat brain hemispheres, brainstem, heart ventricles and kidneys. In all tissues investigated, Na(+)/K(+)-ATPase activity was higher in adults than in neonates but brain tissues presented the most remarkable differences. In these tissues, ouabain inhibition curves for Na(+)/K(+)-ATPase activity revealed the presence of two processes with different sensitivities to ouabain. An increase of approximately sixfold in the expression of the high affinity isoforms was observed between newborn and adult rats. In contrast, the low affinity isoform increased only approximately twofold in brainstem whereas it increased ninefold in brain hemispheres. Unlike brain tissues, a decrease (almost fourfold) in the number of high affinity ouabain binding sites was observed during ontogenesis of the heart. Although limited by the inability to resolve alpha(2) and alpha(3) isoforms, present data indicate that the influence of development on the expression of Na(+)/K(+)-ATPase depends not only on the isoform, but also on the tissue where the enzyme is expressed.     

Multiple virus infections in the honey bee and genome divergence of honey bee viruses

Using uniplex RT-PCR we screened honey bee colonies for the presence of several bee viruses, including black queen cell virus (BQCV), deformed wing virus (DWV), Kashmir bee virus (KBV), and sacbrood virus (SBV), and described the detection of mixed virus infections in bees from these colonies. We report for the first time that individual bees can harbor four viruses simultaneously. We also developed a multiplex RT-PCR assay for the simultaneous detection of multiple bee viruses. The feasibility and specificity of the multiplex RT-PCR assay suggests that this assay is an effective tool for simultaneous examination of mixed virus infections in bee colonies and would be useful for the diagnosis and surveillance of honey bee viral diseases in the field and laboratory. Phylogenetic analysis of putative helicase and RNA-dependent RNA polymerase (RdRp) encoded by viruses reveal that DWV and SBV fall into a same clade, whereas KBV and BQCV belong to a distinct lineage with other picorna-like viruses that infect plants, insects and vertebrates. Results from field surveys of these viruses indicate that mixed infections of BQCV, DWV, KBV, and SBV in the honey bee probably arise due to broad geographic distribution of viruses.     

Dissecting apple tree architecture into genetic, ontogenetic and environmental effects: QTL mapping

The present study aimed to dissect tree architectural plasticity into genetic, ontogenetic and environmental effects over the first 4 years of growth of an apple F1 progeny by means of quantitative traits loci (QTL) mapping. Both growth and branching processes were phenotyped on the consecutive annual shoots of different axes within a tree. For each studied trait, predicted values (best linear unbiased predictors, BLUPs) of the genotypic (G) effect or its interaction with tree age (G×A) and climatic year (G×Y) were extracted from mixed linear models of repeated data. These BLUPs, which are independent from autocorrelations between repeated measurements, were used for QTL mapping. QTL detection power was improved by this two-step approach. For each architectural process, numerous QTLs were detected and some particularly interesting co-localised in common genomic regions, for internode lengthening, top diameter, and number and percentage of axillary shoots. When several QTLs were detected for a given trait, global models were estimated, which explained a maximum of 40% of the total variance for both internode length and top diameter and 28% for branching. QTLs detected for BLUPs of G×Y effects were interpreted as resulting from the interaction between genetic maximal potential of growth and climatic factors, while those for G×A effects were interpreted in relation to tree ontogeny. Most of the latter ones were found to be concomitant with key development stages during which the trait average started to decrease, but with different magnitudes depending on genotype. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Rho GTPase activity in the honey bee mushroom bodies is correlated with age and foraging experience

Foraging experience is correlated with structural plasticity of the mushroom bodies of the honey bee brain. While several neurotransmitter and intracellular signaling pathways have been previously implicated as mediators of these structural changes, none interact directly with the cytoskeleton, the ultimate effector of changes in neuronal morphology. The Rho family of GTPases are small, monomeric G proteins that, when activated, initiate a signaling cascade that reorganizes the neuronal cytoskeleton. In this study, we measured activity of two members of the Rho family of GTPases, Rac and RhoA, in the mushroom bodies of bees with different durations of foraging experience. A transient increase in Rac activity coupled with a transient decrease in RhoA activity was found in honey bees with 4 days foraging experience compared with same-aged new foragers. These observations are in accord with previous reports based on studies of other species of a growth supporting role for Rac and a growth opposing role for RhoA. This is the first report of Rho GTPase activation in the honey bee brain.     

Effects of a juvenile hormone analogue on honey bee foraging behaviour and alarm pheromone production

Worker honey bees treated with 250 μg of the juvenile hormone analogue methoprene shifted from the broodnest to the food storage region prematurely and displayed precocious foraging behaviour. Treatments with 25 and 2.5 μg caused slight but non-significant effects. Methoprene did not influence individual foraging performance as measured by mean number of foraging trips/h, mean amount of time spent foraging/h or mean duration of the total foraging period. Methoprene also induced premature production of two alarm pheromones, 2-heptanone and isopentyl acetate. These results support the hypothesis that juvenile hormone regulates temporal division of labour in the honey bee colony.     

Seasonal trends in honey bee pollen foraging revealed through DNA barcoding of bee-collected pollen

Insectes Sociaux - Recent declines in the abundance and diversity of wild bee species have made it important to understand how introduced species such as honey bees contribute to pollinating native...