Foraging Economics of the Hunt Bumble Bee, a Viable Pollinator for Commercial Agriculture

Globally, there are only five bumble bee (Hymenoptera: Apidae, Bombus) species that have been successfully commercialized for agriculture. The Hunt bumble bee, Bombus huntii Green, 1860, has been recognized as a suitable pollinator of crops and has a broad distribution in western North America, making it a viable candidate for commercialization. In this study, our goal was to characterize the foraging dynamics of B. huntii female workers under open field conditions. To accomplish this goal, we monitored three B. huntii colonies over an 8-wk period in the summer of 2012 in northern Utah. Using marked bees, we studied the relationship between foraging duration/offloading and pollen/nonvisible pollen collection. In total, we observed 921 foraging events across all three colonies. Of our observations, 82% (n = 756) were foraging events that included both a departure and arrival time observation. Average duration of pollen and nonpollen (i.e., nectar) trips across foragers is 41.86 ± 5.65 min (±SE) and 32.18 ± 5.89 min, respectively. Workers spent a significantly longer time offloading pollen in the nest after a foraging trip relative to workers without pollen present on their corbicula. Pollen foraging rate increases over the course of the day, likely due to the time it takes to learn how to forage on a diverse array of flower morphologies. Our study provides data on how long it takes for B. huntii to forage in open field conditions and will be useful when comparing foraging rates in controlled crop systems

Detoxification and stress response genes expressed in a western North American bumble bee, Bombus huntii (Hymenoptera: Apidae)

BACKGROUND: The Hunt bumble bee (Bombus huntii Greene, Hymenoptera: Apidae) is a holometabolous, social insect important as a pollinator in natural and agricultural ecosystems in western North America. Bumble bees spend a significant amount of time foraging on a wide variety of flowering plants, and this activity exposes them to both plant toxins and pesticides, posing a threat to individual and colony survival. Little is known about what detoxification pathways are active in bumble bees, how the expression of detoxification genes changes across life stages, or how the number of detoxification genes expressed in B. huntii compares to other insects. RESULTS: We found B. huntii expressed at least 584 genes associated with detoxification and stress responses. The expression levels of some of these genes, such as those encoding the cytochrome P450s, glutathione S-transferases (GSTs) and glycosidases, vary among different life stages to a greater extent than do other genes. We also found that the number of P450s, GSTs and esterase genes expressed by B. huntii is similar to the number of these genes found in the genomes of other bees, namely Bombus terrestris, Bombus impatiens, Apis mellifera and Megachile rotundata, but many fewer than are found in the fly Drosophila melanogaster. CONCLUSIONS: Bombus huntii has transcripts for a large number of detoxification and stress related proteins, including oxidation and reduction enzymes, conjugation enzymes, hydrolytic enzymes, ABC transporters, cadherins, and heat shock proteins. The diversity of genes expressed within some detoxification pathways varies among the life stages and castes, and we typically identified more genes in the adult females than in larvae, pupae, or adult males, for most pathways. Meanwhile, we found the numbers of detoxification and stress genes expressed by B. huntii to be more similar to other bees than to the fruit fly. The low number of detoxification genes, first noted in the honey bee, appears to be a common phenomenon among bees, and perhaps results from their symbiotic relationship with plants. Many flowering plants benefit from pollinators, and thus offer these insects rewards (such as nectar) rather than defensive plant toxins

The effect of photobleaching on bee (Hymenoptera: Apoidea) setae color and its implications for studying aging and behavior

Historically, bee age has been estimated using measurements of wing wear and integument color change.  These measurements have been useful in studies of foraging ecology and plant-pollinator interactions.  Wing wear is speculated to be affected by the behaviors associated with foraging, nesting, and mating activities.  Setal color change may be an additional parameter used to measure bee age if it is affected by sun exposure during these same activities.  The objectives of this study were to experimentally assess the effect of direct sun exposure on setal color, unicellular hair-like processes of the integument, and determine whether wing wear and integument photobleaching are correlated.  To quantify photobleaching of setae, we measured changes in hue of lab-reared Bombus huntii Greene (Apidae) exposed to natural sunlight.  We found that sun exposure was a significant variable in determining setal bleaching.  To assess the relationship between wing wear and setal photobleaching, we scored wing wear and measured setal hue of B. huntii, Melecta pacifica fulvida Cresson (Apidae), and Osmia integra Cresson (Megachilidae) from museum specimens.  Wing wear and setal hue values were positively correlated for all three species; however, the strength of the relationship varies across bee species as indicated by correlation coefficient estimates.  Our results suggest that setal color change is affected by sun exposure, and is likely an accurate estimate of bee age.  We suggest that future investigations of bee aging consider a suite of morphometric characteristics due to differences in natural history and sociobiology that may be confounded by the use of a single characteristic

Bumble Bee (Hymenoptera: Apidae) Foraging Distance and Colony Density Associated With a Late-Season Mass Flowering Crop

Foraging behaviors of bumble bee workers have been examined in natural habitats, whereas agricultural landscapes, which can provide insights on flight distances to fragmented patches of bloom, have received limited attention. In particular, information on worker flight distances to crops blooming several months after nests have been established is invaluable. Here, we examined foraging patterns of Bombus vosnesenskii Radoszkowski in late-season blooming clover in the agricultural-dominated Willamette Valley in Oregon. Workers from 10 fields collected over 2 yr were assigned to full sibling families (colonies) by using eight microsatellite loci. With estimation of numbers of unseen species, we inferred the presence of 189 colonies from 433 bees genotyped in year 1, and 144 from 296 genotyped the next year. Worker foraging distance was estimated to be at least 11.6 km, half the distance between the most remote fields visited by the same colonies. Numbers of nests contributing workers to each field ranged from 15 to 163. Overall, 165 (50%) colonies foraged in two or more fields, and thus used common resources within the landscape. Estimates of average nest densities in the landscape each year ranged from 0.76/km² to 22.16/km², and highlighted the influences of various study parameters incorporated into the calculation including sample size, distances between sites, and analytical tools used to estimate unsampled individuals. Based on the results, bumble bees can fly long distances, and this could facilitate their survival in fragmented agricultural landscapes. This has important implications for the scale of habitat management in bumble bee conservation programs.Keywords: clover, Bombus, pollinators, microsatellitesKeywords: clover, Bombus, pollinators, microsatellite

Evidence for \u3cem\u3eBombus Occidentalis\u3c/em\u3e (Hymenoptera: Apidae) Populations in the Olympic Peninsula, the Palouse Prairie, and Forests of Northern Idaho

Since the mid-1990s, Bombus occidentalis (Green) has declined from being one of the most common to one of the rarest bumble bee species in the Pacific Northwest of the United States. Although its conservation status is unresolved, a petition to list this species as endangered or threatened was recently submitted to the U.S. Fish and Wildlife Service. To shed light on the conservation situation and inform the U.S. Fish and Wildlife Service decision, we report on the detection and abundance of B. occidentalis following bumble bee collection between 2012 and 2014 across the Pacific Northwest. Collection occurred from the San Juan Islands and Olympic peninsula east to northern Idaho and northeastern Oregon, excluding the arid region in central Washington. B. occidentalis was observed at 23 collection sites out of a total of 234. With the exception of three sites on the Olympic peninsula, all of these were in the southeastern portion of the collection range

Phylogeny and Population Genetic Analyses Reveals Cryptic Speciation in the \u3ci\u3eBombus fervidus\u3c/i\u3e Species Complex (Hymenoptera: Apidae)

Bumble bees (Bombus Latrielle) are significant pollinators of flowering plants due to their large body size, abundant setae, and generalist foraging strategies. However, shared setal coloration patterns among closely and distantly related bumble bee species makes identification notoriously difficult. The advent of molecular genetic techniques has increased our understanding of bumble bee evolution and taxonomy, and enables effective conservation policy and management. Individuals belonging to the North American Bombus fervidus species-complex (SC) are homogenous in body structure but exhibit significant body color phenotype variation across their geographic distribution. Given the uncertainty of the genealogical boundaries within the SC, some authors have synonymized all members of the B. fervidus SC within a single taxon, while others propose an alternative two taxa hypothesis. Operating under the phylogenetic species concept, our analysis supports the hypothesis that there are two independent lineages of bumble bees within the B. fervidus SC. With the current evidence, however, it is not possible to assign valid names to either of them, because both lineages include the color phenotypes found in the original species descriptions of B. fervidus and B. californicus. Cryptic speciation does not seem to be the product of Müllerian mimicry between the clades, because diverging coloration patterns are observed when the distribution of the clades overlaps. Furthermore, within each lineage there is evidence for strong population differentiation that is correlated with geographic distribution rather than color phenotype. In our study, we demonstrate the importance of obtaining a broad sample of multiple populations when conducting lower-level phylogenetic analyses. In addition to improving our knowledge of bumble bee diversification patterns, characterizing the evolutionary history of these pollinators provides the foundation needed to guide contemporary conservation assessments and management strategies

Anomalous conductance oscillations and half-metallicity in atomic Ag-O chains

Using spin density functional theory we study the electronic and magnetic properties of atomically thin, suspended chains containing silver and oxygen atoms in an alternating sequence. Chains longer than 4 atoms develop a half-metallic ground state implying fully spin polarized charge carriers. The conductances of the chains exhibit weak even-odd oscillations around an anomalously low value of 0.1G_0 (G_0 = 2e^2h) which coincide with the averaged experimental conductance in the long chain limit. The unusual conductance properties are explained in terms of a resonating-chain model which takes the reflection probability and phase-shift of a single bulk-chain interface as the only input. The model also explains the conductance oscillations for other metallic chains.Comment: 5 pages, 4 figure

A Nonlethal Method to Examine Non-Apis Bees for Mark-Capture Research

Studies of bee movement and activities across a landscape are important for developing an understanding of their behavior and their ability to withstand environmental stress. Recent research has shown that proteins, such as egg albumin, are effective for mass-marking bees. However, current protein mass-marking techniques require sacrificing individual bees during the data collection process. A nonlethal sampling method for protein mark-capture research is sorely needed, particularly for vulnerable, sensitive, or economically valuable species. This study describes a nonlethal sampling method, in which three non-Apis bee species (Bombus bifarius Cresson [Hymenoptera: Apidae], Osmia lignaria Say [Hymenoptera: Megachilidae], and Megachile rotundata Fabricius [Hymenoptera: Megachilidae]) were tested for a unique protein marker by immersing them momentarily in saline buffer and releasing them. Results showed that an egg albumin-specific enzyme-linked immunosorbent assay was 100% effective at detecting the protein on bees that were sampled nonlethally. Furthermore, this sampling method did not have an impact on bee survivorship, suggesting that immersing bees in buffer is a reliable and valid surrogate to traditional, destructive sampling methods for mark-capture bee studies

An improved competitive inhibition enzymatic immunoassay method for tetrodotoxin quantification

Quantifying tetrodotoxin (TTX) has been a challenge in both ecological and medical research due to the cost, time and training required of most quantification techniques. Here we present a modified Competitive Inhibition Enzymatic Immunoassay for the quantification of TTX, and to aid researchers in the optimization of this technique for widespread use with a high degree of accuracy and repeatability

A Homeotic Shift Late in Development Drives Mimetic Color Variation in a Bumble Bee

Natural phenotypic radiations, with their high diversity and convergence, are well-suited for informing how genomic changes translate to natural phenotypic variation. New genomic tools enable discovery in such traditionally nonmodel systems. Here, we characterize the genomic basis of color pattern variation in bumble bees (Hymenoptera, Apidae, Bombus), a group that has undergone extensive convergence of setal color patterns as a result of Müllerian mimicry. In western North America, multiple species converge on local mimicry patterns through parallel shifts of midabdominal segments from red to black. Using genome-wide association, we establish that a cis-regulatory locus between the abdominal fate-determining Hox genes, abd-A and Abd-B, controls the red–black color switch in a western species, Bombus melanopygus. Gene expression analysis reveals distinct shifts in Abd-B aligned with the duration of setal pigmentation at the pupal–adult transition. This results in atypical anterior Abd-B expression, a late developmental homeotic shift. Changing expression of Hox genes can have widespread effects, given their important role across segmental phenotypes; however, the late timing reduces this pleiotropy, making Hox genes suitable targets. Analysis of this locus across mimics and relatives reveals that other species follow independent genetic routes to obtain the same phenotypes