Evidence of exploitative competition between honey bees and native bees in two California landscapes.

Human-mediated species introductions provide real-time experiments in how communities respond to interspecific competition. For example, managed honey bees Apis mellifera (L.) have been widely introduced outside their native range and may compete with native bees for pollen and nectar. Indeed, multiple studies suggest that honey bees and native bees overlap in their use of floral resources. However, for resource overlap to negatively impact resource collection by native bees, resource availability must also decline, and few studies investigate impacts of honey bee competition on native bee floral visits and floral resource availability simultaneously. In this study, we investigate impacts of increasing honey bee abundance on native bee visitation patterns, pollen diets, and nectar and pollen resource availability in two Californian landscapes: wildflower plantings in the Central Valley and montane meadows in the Sierra. We collected data on bee visits to flowers, pollen and nectar availability, and pollen carried on bee bodies across multiple sites in the Sierra and Central Valley. We then constructed plant-pollinator visitation networks to assess how increasing honey bee abundance impacted perceived apparent competition (PAC), a measure of niche overlap, and pollinator specialization (d'). We also compared PAC values against null expectations to address whether observed changes in niche overlap were greater or less than what we would expect given the relative abundances of interacting partners. We find clear evidence of exploitative competition in both ecosystems based on the following results: (1) honey bee competition increased niche overlap between honey bees and native bees, (2) increased honey bee abundance led to decreased pollen and nectar availability in flowers, and (3) native bee communities responded to competition by shifting their floral visits, with some becoming more specialized and others becoming more generalized depending on the ecosystem and bee taxon considered. Although native bees can adapt to honey bee competition by shifting their floral visits, the coexistence of honey bees and native bees is tenuous and will depend on floral resource availability. Preserving and augmenting floral resources is therefore essential in mitigating negative impacts of honey bee competition. In two California ecosystems, honey bee competition decreases pollen and nectar resource availability in flowers and alters native bee diets with potential implications for bee conservation and wildlands management.

Abundant, distinct, and seasonally dynamic bee community in the canopy-aerosphere interface above a temperate forest.

Our understanding of how bees (Apoidea) use temperate forests is largely limited to sampling the understory and forest floor. Studies over the last decade have demonstrated that bee communities are vertically stratified within forests, yet the ecology of bee assemblages immediately above the canopy, the canopy-aerosphere interface, remains unexplored. We sampled and compared bee communities above the canopy of a temperate forest to the understory (1 m), midstory (10 m), and canopy (20 m) on the campus of the University of Massachusetts, in Amherst, Massachusetts, United States from April to August, 2021. Overall, we found that assemblages above the canopy had more bees than in the understory, were distinct in composition from all other strata, and included the greatest proportion of unique species. Bee abundance and species richness were highest in the understory throughout the spring (April and May) and decreased as the season progressed, while bee abundance and species richness at higher strata increased into the summer months. We also found that bees with preferences to nest in moist and rotting wood were largely restricted to canopy and midstory strata. We conclude that bee assemblages occupying the space above the forest canopy are abundant and diverse, and their unique composition suggests that this canopy-aerosphere interface plays an additional role in the bee community of temperate forests. Alternatively, our findings question how forest bee communities should be defined while highlighting the need for research on fundamental processes governing species stratification in and above the canopy.

Honey bee introductions displace native bees and decrease pollination of a native wildflower.

Introduced species can have cascading effects on ecological communities, but indirect effects of species introductions are rarely the focus of ecological studies. For example, managed honey bees (Apis mellifera) have been widely introduced outside their native range and are increasingly dominant floral visitors. Multiple studies have documented how honey bees impact native bee communities through floral resource competition, but few have quantified how these competitive interactions indirectly affect pollination and plant reproduction. Such indirect effects are hard to detect because honey bees are themselves pollinators and may directly impact pollination through their own floral visits. The potentially huge but poorly understood impacts that non-native honey bees have on native plant populations combined with increased pressure from beekeepers to place hives in U.S. National Parks and Forests makes exploring impacts of honey bee introductions on native plant pollination of pressing concern. In this study, we used experimental hive additions, field observations, as well as single-visit and multiple-visit pollination effectiveness trials across multiple years to untangle the direct and indirect impacts of increasing honey bee abundance on the pollination of an ecologically important wildflower, Camassia quamash. We found compelling evidence that honey bee introductions indirectly decrease pollination by reducing nectar and pollen availability and competitively excluding visits from more effective native bees. In contrast, the direct impact of honey bee visits on pollination was negligible, and, if anything, negative. Honey bees were ineffective pollinators, and increasing visit quantity could not compensate for inferior visit quality. Indeed, although the effect was not statistically significant, increased honey bee visits had a marginally negative impact on seed production. Thus, honey bee introductions may erode longstanding plant-pollinator mutualisms, with negative consequences for plant reproduction. Our study calls for a more thorough understanding of the indirect effects of species introductions and more careful coordination of hive placements.

Bacterial and Fungal Symbionts in Pollen Provisions of a Native Solitary Bee in Urban and Rural Environments.

Among insects, symbionts such as bacteria and fungi can be linked to their physiology and immature development, and in some cases are part of a defense system against parasites and diseases. Current bacterial and fungal symbiont associations in solitary bees are understudied, especially in the Pacific Northwest region of the USA. We collected pollen provisions from the native spring-foraging solitary bee, Osmia lignaria Say, across two distinct foraging periods over 2 years at 22 sites along an urban-to-rural gradient in western Washington. We then used next-generation sequencing to identify bacterial and fungi within pollen provisions and assessed the effect of their richness and diversity on O. lignaria larval development success and adult emergence. We detected a significantly positive relationship between bacterial diversity in pollen with O. lignaria larval developmental success, and higher bacterial richness and diversity during the later foraging period. Fungal generic richness and diversity decreased with increasing plant richness. Although neither was associated with O. lignaria developmental success, we did detect Ascosphaera spp. known to be pathogenic to O. lignaria and other bee species. Neither bacterial or fungal richness or diversity was affected by site type when classified as urban or rural. This study provides new information on bacterial and fungal symbionts present in pollen provisions of a native solitary bee when foraging across urban and rural areas of the Pacific Northwest.

Addressing Detection Uncertainty in Bombus affinis (Hymenoptera: Apidae) Surveys Can Improve Inferences Made From Monitoring.

The U.S. Fish and Wildlife Service developed national guidelines to track species recovery of the endangered rusty patched bumble bee [Bombus affinis Cresson (Hymenoptera: Apidae)] and to investigate changes in species occupancy across space and time. As with other native bee monitoring efforts, managers have specifically acknowledged the need to address species detection uncertainty and determine the sampling effort required to infer species absence within sites. We used single-season, single-species occupancy models fit to field data collected in four states to estimate imperfect detection of B. affinis and to determine the survey effort required to achieve high confidence of species detection. Our analysis revealed a precipitous, seasonal, decline in B. affinis detection probability throughout the July through September sampling window in 2021. We estimated that six, 30-min surveys conducted in early July are required to achieve a 95% cumulative detection probability, whereas >10 surveys would be required in early August to achieve the same level of confidence. Our analysis also showed B. affinis was less likely to be detected during hot and humid days and at patches of reduced habitat quality. Bombus affinis was frequently observed on Monarda fistulosa (Lamiales: Lamiaceae), followed by [Pycnanthemum virginianum Rob. and Fernald (Lamiales: Lamiaceae)], Eutrochium maculatum Lamont (Asterales: Asteraceae), and Veronicastrum virginicum Farw. (Lamiales: Plantaginaceae). Although our research is focused on B. affinis, it is relevant for monitoring other bumble bees of conservation concern, such as B. occidentalis Greene (Hymenoptera: Apidae) and B. terricola Kirby (Hymenoptera: Apidae) for which monitoring efforts have been recently initiated and occupancy is a variable of conservation interest.

Individual Dietary Specialization in a Generalist Bee Varies across Populations but Has No Effect on the Richness of Associated Microbial Communities.

AbstractDespite the increasingly documented occurrence of individual specialization, the relationship between individual consumer interactions and diet-related microbial communities in wild populations is still unclear. Using data from nests of Ceratina australensis from three different wild bee populations, we combine metabarcoding and network approaches to explore the existence of individual variation in resource use within and across populations and whether dietary specialization affects the richness of pollen-associated microbes. We reveal the existence of marked dietary specialization. In the most specialized population, we also show that individuals' diet breadth was positively related to the richness of fungi but not bacteria. Overall, individual specialization appeared to have a weak or negligible effect on the microbial richness of nests, suggesting that different mechanisms beyond environmental transmission may be at play regarding microbial acquisition in wild bees.

Brazilian stingless bee honey: Physicochemical properties and aliphatic organic acids content.

This study aimed to investigate for the first time fourteen aliphatic organic acids (AOA) in honeys produced by different species of Brazilian stingless bees (Melipona bicolor, Scaptotrigona bipunctata, Melipona quadrifasciata, and Melipona marginata) and characterize them regarding their physicochemical properties. Thirteen AOAwere quantified in the samples, in which five of them (malonic, fumaric, glycolic, glutaric, and propionic acids) were identified for the first time instingless bee honey (SBH). Acetic, gluconic, and lactic acids were predominant in all the samples analyzed varying from 0.0067 ± 0.0001 to 1.5993 ± 0.0003 g 100 g-1, 0.0808 ± 0.0007 to 1.3460 ± 0.0006 g 100 g-1, and 0.0370 ± 0.000 to 0.5760 ± 0.0006 g 100 g-1, respectively. Most physicochemical properties showed significant differences (p < 0.05) among the samples. However, it was observed that the water activity (Aw) did not differ significantly between honey samples produced by the same species. Moreover, it is important to highlight the high moisture content, Aw, and free acidity that were found in the range of 29.6 to 40.1 g 100 g-1, 0.75 to 0.84, and 37.8 to 123 mEq kg-1, respectively. This information reinforces such peculiar characteristics of SBH and a need to deeply investigate the physical and chemical characteristics of honey from different species of stingless bees. In conclusion, it was observed that the honey samples of the different stingless bee species presented a great variation regarding their AOA content, highlighting acetic, gluconic, and lactic acids as the major AOA in all the samples. However, since this was an exploratory study, it was not possible to find any correlation between honey produced by the same species.

Patch utilization and flower visitations by wild bees in a honey bee-dominated, grassland landscape.

Understanding habitat needs and patch utilization of wild and managed bees has been identified as a national research priority in the United States. We used occupancy models to investigate patterns of bee use across 1030 transects spanning a gradient of floral resource abundance and richness and distance from apiaries in the Prairie Pothole Region (PPR) of the United States. Estimates of transect use by honey bees were nearly 1.0 during our 3.5-month sampling period, suggesting honey bees were nearly ubiquitous across transects. Wild bees more frequently used transects with higher flower richness and more abundant flowers; however, the effect size of the native flower abundance covariate ( ß ^ native  = 3.90 ± 0.65 [1SE]) was four times greater than the non-native flower covariate ( ß ^ n o n - n a t i v e  = 0.99 ± 0.17). We found some evidence that wild bee use was lower at transects near commercial apiaries, but the effect size was imprecise ( ß ^ distance  = 1.4 ± 0.81). Honey bees were more frequently detected during sampling events with more non-native flowers and higher species richness but showed an uncertain relationship with native flower abundance. Of the 4039 honey bee and flower interactions, 85% occurred on non-native flowers, while only 43% of the 738 wild bee observations occurred on non-native flowers. Our study suggests wild bees and honey bees routinely use the same resource patches in the PPR but often visit different flowering plants. The greatest potential for resource overlap between honey bees and wild bees appears to be for non-native flowers in the PPR. Our results are valuable to natural resource managers tasked with supporting habitat for managed and wild pollinators in agroecosystems.

Corridors through time: Does resource continuity impact pollinator communities, populations, and individuals?

Spatial aspects of connectivity have received considerable attention from ecologists and conservationists, yet temporal connectivity, the periodic linking of habitats, plays an equally important, but largely overlooked role. Different biological and biophysical attributes of ecosystems underpin temporal connectivity, but here we focus on resource continuity, the uninterrupted availability of foraging sites. We test the response of pollinators to resource continuity at community, population, and individual levels using a novel natural experiment consisting of farms with either single or sequential cropping systems. We found significant effects at the population level; colony density of an important crop pollinator (Bombus impatiens L.) was greater when crop floral resources were continuously available. However, we did not find significant effects at the community or individual level; wild bee abundance, diversity and body size did not respond to resource continuity. Raspberry farms with greater early season resources provided by blueberry had greater bumble bee populations, suggesting beneficial effects on resource availability due to crop diversity. Better understanding the impact of resource continuity via crop diversity on broader patterns of biodiversity is essential for the co-management of biodiversity and ecosystem services.

Bee diversity in secondary forests and coffee plantations in a transition between foothills and highlands in the Guatemalan Pacific Coast.

BACKGROUND: Although conservation of pristine habitats is recognized in many countries as crucial for maintaining pollinator diversity, the contribution of secondary forest conservation is poorly recognized in the Latin American context, such as in Guatemala. San Lucas Tolimán (SLT) is a high-quality coffee production region from the Atitlan Province, which has the second highest deciduous forest cover in Guatemala and pristine forest is prioritized for conservation. In contrast, secondary forest protection is undetermined, since these forests are normally removed or strongly affected by coffee farming practices. This situation may affect the diversity of native pollinators, mainly bees, which usually rely on the secondary forest for food resources. METHODS: We conducted a study to investigate the importance of secondary forests around the SLT coffee plantations (Coffea arabica L.) for pollinators. We compared bee diversity (richness, abundance and composition) in secondary forests of different age and coffee plantations with diverse farming techniques. Being the first study of pollinators in Guatemalan coffee plantations, we also recorded data for an entire year (2013-2014) in order to describe bee seasonality. RESULTS: We found significant differences in bee diversity between the coffee plantations and secondary forests, particularly early secondary forests showed higher bee abundances but diversity indices were similar between different vegetation type plots. In the early dry season, secondary forests showed the greatest native bee diversity. During the late dry season, when the coffee was flowering, honey bees were dominant in the same plots. This study provides important management insights to support the conservation of pollinators, since our results offer guidelines to improve coffee production by increasing native pollinator diversity.

Along urbanization sprawl, exotic plants distort native bee (Hymenoptera: Apoidea) assemblages in high elevation Andes ecosystem.

Native bees contribute a considerable portion of pollination services for endemic as well as introduced plant species. Their decline has been attributed to several human-derived influences including global warming as well as the reduction, alteration, and loss of bees' habitat. With human expansion comes along the introduction of exotic plant species with negative impacts over native ecosystems. Anthropic effects may even have a deeper impact on communities adapted to extreme environments, such as high elevation habitats, where abiotic stressors alone are a natural limitation to biodiversity. Among these effects, the introduction of exotic plants and urbanization may have a greater influence on native communities. In this work, we explored such problems, studying the relationship between the landscape and its effect over richness and abundance of native bees from the subandean belt in the Andes mountain chain. Furthermore, we investigated the effects of exotic plant abundance on this high-altitude bee assemblage. Despite the landscape not showing an effect over bee richness and abundance, exotic plants did have a significant influence over the native bee assemblage. The abundance of exotic plants was associated with a relative increase in the proportion of small and medium bee species. Moreover, Halictidae was the only family that appeared to be favored by an increase in the abundance of exotic plant species. We discuss these results and the urgent need for further research of high-altitude environments due to their vulnerability and high endemicity.

Effect of GF-120 (Spinosad) Aerial Sprays on Colonies of the Stingless Bee Scaptotrigona mexicana (Hymenoptera: Apidae) and the Honey Bee (Hymenoptera: Apidae).

Despite their relevant contribution to the conservation of tropical ecosystems and crop productivity through pollination, the stingless bees (Apidae: Meliponini) can be considered a group of neglected species in the assessment of pesticides upon nontarget organisms. In this article, we evaluated the effect of aerial sprays of the spinosad-based fruit fly toxic bait GF-120 upon colonies of the stingless bee Scaptotrigona mexicana Guérin (Hymenoptera: Apidae), an economically important and abundant species in some landscapes of Mexico, located in mango orchards. Colonies of the honey bee Apis mellifera L. (Hymenoptera: Apidae) were used for comparison. Eight colonies (four of A. mellifera and four of S. mexicana) were moved into each of two mango orchards, one was used as a control, with no insecticide application, and other received five weekly aerial sprays of GF-120. Foraging activity and strength of colonies of both species were measured nine times over the fruiting season, previous, during and after insecticide application. We did not find a significant difference in foraging activity and strength between exposed and control colonies of A. mellifera during the observation period. However, colonies of S. mexicana seemed to be affected by the exposure, as revealed by a reduction in colony strength. However, 1 yr later, with no insecticide applications, the colonies of both species were evaluated and found to be in good conditions. Our results showed that weekly aerial sprays of GF-120 are unlikely to generate acute poisoning in both species, even if in acute toxicity tests this product has been found to be highly active.

Organochlorine Pesticides in Honey and Pollen Samples from Managed Colonies of the Honey Bee Apis mellifera Linnaeus and the Stingless Bee Scaptotrigona mexicana Guérin from Southern, Mexico.

In this paper, we show the results of investigating the presence of organochlorine pesticides in honey and pollen samples from managed colonies of the honey bee, Apis mellifera L. and of the stingless bee Scaptotrigona mexicana Guérin. Three colonies of each species were moved into each of two sites. Three samples of pollen and three samples of honey were collected from each colony: the first collection occurred at the beginning of the study and the following ones at every six months during a year. Thus the total number of samples collected was 36 for honey (18 for A. mellifera and 18 for S. mexicana) and 36 for pollen (18 for A. mellifera and 18 for S. mexicana). We found that 88.44% and 93.33% of honey samples, and 22.22% and 100% of pollen samples of S. mexicana and A. mellifera, respectively, resulted positive to at least one organochlorine. The most abundant pesticides were Heptaclor (44% of the samples), γ-HCH (36%), DDT (19%), Endrin (18%) and DDE (11%). Despite the short foraging range of S. mexicana, the number of pesticides quantified in the honey samples was similar to that of A. mellifera. Paradoxically we found a small number of organochlorines in pollen samples of S. mexicana in comparison to A. mellifera, perhaps indicating a low abundance of pollen sources within the foraging range of this species.

Lactobacillus micheneri sp. nov., Lactobacillus timberlakei sp. nov. and Lactobacillus quenuiae sp. nov., lactic acid bacteria isolated from wild bees and flowers.

Gram-stain-positive, rod-shaped, non-spore forming bacteria have been isolated from flowers and the guts of adult wild bees in the families Megachilidae and Halictidae. Phylogenetic analysis of the 16S rRNA gene indicated that these bacteria belong to the genus Lactobacillus, and are most closely related to the honey-bee associated bacteria Lactobacillus kunkeei (97.0 % sequence similarity) and Lactobacillus apinorum (97.0 % sequence similarity). Phylogenetic analyses of 16S rRNA genes and six single-copy protein coding genes, in situ and in silico DNA-DNA hybridization, and fatty-acid profiling differentiates the newly isolated bacteria as three novel Lactobacillus species: Lactobacillus micheneri sp. nov. with the type strain Hlig3T (=DSM 104126T,=NRRL B-65473T), Lactobacillus timberlakei with the type strain HV_12T (=DSM 104128T,=NRRL B-65472T), and Lactobacillus quenuiae sp. nov. with the type strain HV_6T (=DSM 104127T,=NRRL B-65474T).

Economic Risk of Bee Pollination in Maine Wild Blueberry, Vaccinium angustifolium.

Recent pollinator declines highlight the importance of evaluating economic risk of agricultural systems heavily dependent on rented honey bees or native pollinators. Our study analyzed variability of native bees and honey bees, and the risks these pose to profitability of Maine's wild blueberry industry. We used cross-sectional data from organic, low-, medium-, and high-input wild blueberry producers in 1993, 1997-1998, 2005-2007, and from 2011 to 2015 (n = 162 fields). Data included native and honey bee densities (count/m2/min) and honey bee stocking densities (hives/ha). Blueberry fruit set, yield, and honey bee hive stocking density models were estimated. Fruit set is impacted about 1.6 times more by native bees than honey bees on a per bee basis. Fruit set significantly explained blueberry yield. Honey bee stocking density in fields predicted honey bee foraging densities. These three models were used in enterprise budgets for all four systems from on-farm surveys of 23 conventional and 12 organic producers (2012-2013). These budgets formed the basis of Monte Carlo simulations of production and profit. Stochastic dominance of net farm income (NFI) cumulative distribution functions revealed that if organic yields are high enough (2,345 kg/ha), organic systems are economically preferable to conventional systems. However, if organic yields are lower (724 kg/ha), it is riskier with higher variability of crop yield and NFI. Although medium-input systems are stochastically dominant with lower NFI variability compared with other conventional systems, the high-input system breaks even with the low-input system if honey bee hive rental prices triple in the future.

Using Publicly Available Data to Quantify Plant-Pollinator Interactions and Evaluate Conservation Seeding Mixes in the Northern Great Plains.

Concern over declining pollinators has led to multiple conservation initiatives for improving forage for bees in agroecosystems. Using data available through the Pollinator Library (npwrc.usgs.gov/pollinator/), we summarize plant-pollinator interaction data collected from 2012-2015 on lands managed by the U.S. Fish and Wildlife Service and private lands enrolled in U.S. Department of Agriculture conservation programs in eastern North Dakota (ND). Furthermore, we demonstrate how plant-pollinator interaction data from the Pollinator Library and seed cost information can be used to evaluate hypothetical seeding mixes for pollinator habitat enhancements. We summarize records of 314 wild bee and 849 honey bee (Apis mellifera L.) interactions detected on 63 different plant species. The wild bee observations consisted of 46 species, 15 genera, and 5 families. Over 54% of all wild bee observations were represented by three genera-Bombus, Lassioglossum, and Melissodes. The most commonly visited forbs by wild bees were Monarda fistulosa, Sonchus arvensis, and Zizia aurea. The most commonly visited forbs by A. mellifera were Cirsium arvense, Melilotus officinalis, and Medicago sativa. Among all interactions, 13% of A. mellifera and 77% of wild bee observations were made on plants native to ND. Our seed mix evaluation shows that mixes may often need to be tailored to meet the unique needs of wild bees and managed honey bees in agricultural landscapes. Our evaluation also demonstrates the importance of incorporating both biologic and economic information when attempting to design cost-effective seeding mixes for supporting pollinators in a critically important part of the United States.

Measuring partner choice in plant-pollinator networks: using null models to separate rewiring and fidelity from chance.

Recent studies of mutualistic networks show that interactions between partners change across years. Both biological mechanisms and chance could drive these patterns, but the relative importance of these factors has not been separated. We established a field experiment consisting of 102 monospecific plots of 17 native plant species, from which we collected 6713 specimens of 52 bee species over four years. We used these data and a null model to determine whether bee species' foraging choices varied more or less over time beyond the variation expected by chance. Thus we provide the first quantitative definition of rewiring and fidelity as these terms are used in the literature on interaction networks. All 52 bee species varied in plant partner choice across years, but for 27 species this variation was indistinguishable from random partner choice. Another 11 species showed rewiring, varying more across years than expected by chance, while 14 species showed fidelity, indicating that they both prefer certain plant species and are consistent in those preferences across years. Our study shows that rewiring and fidelity both exist in mutualist networks, but that once sampling effects have been accounted for, they are less common than has been reported in the ecological literature.

Evidence for Bombus occidentalis (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.

Using Nonmetric Multidimensional Scaling to Analyze Bee Visitation in East Tennessee Crops as an Indicator of Pollination Services Provided by Honey Bees (Apis mellifera L.) and Native Bees.

This study investigated bee visitation on 10 agricultural crops grown on diverse small farms in Tennessee to determine the abundance of native bees and honey bees and the partitioning of visitation among crops. Summaries for each crop are used to generate mean proportions of bee visitation by categories of bees. This shows that native bee visits often occur as frequently, or in greater proportions than non-native honey bee visits. Visitation across multiple crops is then analyzed together with nonmetric multidimensional scaling to show how communities of bees that provide crop pollination change depending on the crop. Within squash and pumpkin plantings, continuous and discrete factors, such as "time of day" and "organic practices," further explain shifts in the community composition of flower visitors. Results from this study show that native bees frequently visit flowers on various crops, indicating that they are likely contributing to pollination services in addition to honey bees. Furthermore, the community of bees visiting flowers changes based on crop type, phenology, and spatial-temporal factors. Results suggest that developing pollinator conservation for farms that grow a wide variety of crops will likely require multiple conservation strategies. Farms that concentrate on a single crop may be able to tailor conservation practices toward the most important bees in their system and geographic locale.

Survey of Soybean Insect Pollinators: Community Identification and Sampling Method Analysis.

Soybean, Glycine max (L.) Merrill, flowers can be a source of nectar and pollen for honey bees, Apis mellifera L. (Hymenoptera: Apidae), wild social and solitary bees (Hymenoptera: Apoidea), and flower-visiting flies (Diptera). Our objectives were to describe the pollinator community in soybean fields, determine which sampling method is most appropriate for characterizing their abundance and diversity, and gain insight into which pollinator taxa may contact soybean pollen. We compared modified pan traps (i.e., bee bowls), yellow sticky traps, and sweep nets for trapping pollinators in Iowa soybean fields when soybeans were blooming (i.e., reproductive stages R1-R6) during 2011 and 2012. When all trap type captures were combined, we collected 5,368 individuals and at least 50 species. Per trap type, the most pollinators were captured in bee bowls (3,644 individuals, 44 species), yellow sticky traps (1,652 individuals, 32 species), and sweep nets (66 individuals, 10 species). The most abundant species collected include Agapostemon virescens F. and Lasioglossum (Dialictus) species (Hymenoptera: Halictidae), Melissodes bimaculata Lepeletier (Hymenoptera: Apidae), and Toxomerus marginatus Say (Diptera: Syrphidae). To determine if these pollinators were foraging on soybean flowers, we looked for soybean pollen on the most abundant bee species collected that had visible pollen loads. We found soybean pollen alone or intermixed with pollen grains from other plant species on 29 and 38% of the bees examined in 2011 and 2012, respectively. Our data suggest a diverse community of pollinators-composed of mostly native, solitary bees-visit soybean fields and forage on their flowers within Iowa.