Honey Bee Abundance Research Articles

Comparing the Efficacy of Single and Multiple Visits by Honey and Solitary Bees on Sunflower Seed Production

Sunflower (Helianthus annuus L.) is an important oil seed crop with a considerable acreage of cultivated hybrids in Pakistan. Sunflower crops depend on insect pollination for seed setting, as it attracts diverse pollinator fauna, mainly due to pollen and nectar availability. This study was conducted in the agricultural landscape of Multan, Pakistan, to evaluate the role of native and social bees in sunflower seed production. The abundance and diversity of pollinators were assessed. Effectiveness was tested regarding foraging behavior, including visitation rate, stay time, and seed set efficacy for single and multiple visits (5, 10, 15). Additionally, various reproductive success parameters were recorded: flower head (pseudanthium) diameter, flower head weight, seed weight/flower head, and number of seed/flower head. The results showed that the relative abundance of honey bees was the highest (77%) in both years, followed by solitary bees (17%), while syrphid flies were the least abundant (6%) on sunflower. Among honey bees, Apis mellifera and A. dorsata were the most abundant in both years, followed by the solitary bee Xylocopa sp. Furthermore, in single and multiple seed set efficacy (5 and 10 visits), the solitary bee Xylocopa sp. produced the maximum seeds, followed by A. mellifera. Higher seed production could be achieved with a focused conservation plan of solitary and managed bees on sunflower.

Preliminary new study indicates possible dramatic decline in the diversity of insects visiting flowers of Jarrah (Eucalyptus marginata) in Kings Park over 26 Years

The recent decline of terrestrial insects in many parts of the world is of growing concern due to the fundamental ecosystem services they perform. Pollination is a vital ecosystem service predominantly performed by insects, with inestimable environmental and economic benefits. Accurate assessment and management of insect pollinator declines, and of other ecosystem impacts are hindered by a lack of long-term monitoring data and notably an absence of Southern Hemisphere studies. This preliminary study aims to address some of these gaps by determining if the diversity of insect floral visitors and potential pollinators of the canopy tree species Jarrah (Eucalyptus marginata) within Kings Park may have changed over 26 years by replicating the methods employed by previous research (undertaken by Yates et al. in 2005). Additionally, this study aims to determine if the relative abundance of the introduced European honeybee (Apis mellifera) compared to native bees visiting Jarrah flowers may have also changed. We observed insect visitors to flowers at three trees across the morning, midday, and evening over three consecutive days in mid-December 2023 (peak flowering). A total of 3023 individual observations were made, recording insects of 7 orders, 25 families, 39 genera, and 45 species. We found that abundances were comparable to 26 years ago but found a substantial shift in the composition of insect visitors with 46% less species documented and only 25% of species reoccurring. Ten additional families were observed that were not documented 26 years ago, with most visitors capable of performing pollination to varying efficacies. Ants had replaced the European honeybee as the most common visitor to Jarrah flowers, and while the relative abundance of honeybees was still significantly greater than native bees, the proportion of honeybee visitors had declined, at least at the time of our study. The documented shift in the composition of Jarrah insect pollinators should be confirmed by more replicated studies in Kings Park, and highlights the importance of long-term monitoring, and the need for further avenues of urban pollination research to accurately assess and address any widespread decline of insects. This is important for protecting the pollination services that insect pollinators provide at local and global scales.

Pollinator functional group abundance and floral heterogeneity in an agroecological context affect mating patterns in a self-incompatible wild plant.

Restoration of seminatural field margins can elevate pollinator activity. However, how they support wild plant gene flow through interactions between pollinators and spatiotemporal gradients in floral resources remains largely unknown. Using a farm-scale experiment, we tested how mating outcomes (expected heterozygosity and paternity correlation) of the wild, self-incompatible plant Cyanus segetum transplanted into field margins (sown wildflower or grass-legume strips) were affected by the abundance of different pollinator functional groups (defined by species traits). We also investigated how the maternal plant attractiveness, conspecific pollen donor density, and heterospecific floral richness and density interacted with pollinator functional group abundance to modulate C. segetum mating outcomes. Multiple paternity increased (=lower paternity correlation) with greater local abundance of hoverflies (syrphids) and female medium-sized wild bees (albeit the latter's effect diminished with decreasing maternal plant attractiveness), and the presence of male bumblebees (Bombus) under low local floral richness. Cyanus segetum progeny genetic diversity increased with male Bombus presence but decreased with greater abundance of syrphids and honey bees (Apis mellifera). Overall, field margins supported plant-pollinator interactions ensuring multiple paternity and conservation of allelic diversity in C. segetum progeny. The contribution to plant mating outcomes of different pollinator functional groups was dictated by their local abundance or traits affecting pollen transfer efficiency. The local floral richness or maternal plant attractiveness sometimes modulated these relationships. This complex response of wild plant mating patterns to community interactions has implications for the use of field margins to restore functional pollination systems in farmed landscapes.

Examination of intestinal microbiota abundance of honey bees supplemented and unsupplemented with probiotic bacteria by QPCR

The aim of this study is to compare the bacterial load in the guts of honey bees supported and unsupplemented with probiotic supplements. To investigate the effects of a commercial bee probiotic containing different Lactobacillus species and different spice extracts on the composition of the gut microbiota of honey bees, QPCR counts of Lactobacillus spp. and Firmicutes phylum gene copies in gut mixtures from 12 different bee groups with and without probiotic supplementation were performed. There was a significant difference between the levels of Lactobacillus spp. in the guts of both groups. When Lactobacillus spp. levels in the guts of honey bees not given probiotics were compared to the Lactobacillus spp. levels in the guts of honey bees given probiotics, it was determined that there was an approximately 5.5-fold difference. However, it was observed that there was no significant difference in the Firmicutes load in the bee guts of both groups. These findings show that the applied probiotic formulation significantly affects the intestinal microbiome of healthy individuals and provides a proportional change in microbial abundance, especially in terms of Lactobacillus spp.

Relation between honey bee abundance and wild bee communities in Moroccan agro-ecosystems

Relation between honey bee abundance and wild bee communities in Moroccan agro-ecosystems

Wildflower plantings and honeybee competition impact nutritional quality of wild bee diets

Abstract Wildflower habitats planted along field borders are a widely promoted strategy for supporting bees in agricultural landscapes. However, honeybees (Apis mellifera), which are often stocked at high densities in crop lands can compete with wild bees for pollen and nectar, potentially limiting the successfulness of wildflower plantings in supporting diverse bee communities. Using weekly samples of five study sites in Northern California we assessed how plants in pollinator‐friendly seed mixes varied in their ability to provide bees with abundant and nutritious pollen under intense honeybee competition. We quantified pollen production, protein and lipid content, and end‐of‐day pollen availability for different plant species. We also sampled bee visits to flowers and assessed the composition of pollen on bee bodies. Using these data, we investigate how the nutritional quality of pollen in wildflower plantings and honeybee abundance impacted native bee pollen nutrition. Bees collected more nutritious pollen (i.e. pollen with more protein) from plantings with more nutritious plant species (i.e. sites with more high‐protein plants). However, as honeybee abundance increased, the nutritional quality of native bee diets declined. We also detected important interactions between honeybee abundance and the nutritional quality of flowers in plantings, such that, for some bee taxa, there was no impact of competition on pollen diet quality in high‐nutrition plantings. Synthesis and applications: Our study reveals that honeybee competition can reduce the nutritional quality of native bee diets. From an applied conservation perspective, we therefore recommend that honeybee introductions in natural areas be approached with extreme caution. However, our results also suggest that high‐protein flower plantings could mitigate negative effects of honeybee competition in managed landscapes. Where simultaneous support of managed and wild bees is a key management objective, we recommend including high‐protein plant species in plant mixes to support diverse bee populations.

Biodiversity measures of a grassland plant-pollinator community are resilient to the introduction of honey bees (Apis mellifera).

The prairies of Canada support a diversity of insect pollinators that contribute pollination services to flowering crops and wild plants. Habitat loss and use of managed pollinators has increased conservation concerns for wild pollinators, as mounting evidence suggests that honey bees (Apis mellifera) may reduce their diversity and abundance. Plant-pollinator community analyses often omit non-bee pollinators, which can be valuable contributors to pollination services. Here, we experimentally introduced honey bees to examine how their abundance affects the species richness, diversity, abundance, species composition, interaction richness, and interaction diversity of all wild pollinators, and of four higher taxa separately. We identified all insect pollinators and analyzed how honey bee abundance affected the above biodiversity metrics, controlling for flower abundance and flower species richness. Even with high honey bee densities, there was no change to any of these variables, except that beetle species diversity increased. All other taxa had no significant relationship to honey bee abundance. Considering the widespread use of managed honey bees, the effect they have on wild pollinators should be firmly established. Our results suggest that honey bees have little to no short-term impact on the wild pollinator community or its interactions with plants in this native grassland.

Evidence of introduced honeybees (Apis mellifera) as pollen wasters in orchid pollination

Biological invasions threaten global biodiversity, altering landscapes, ecosystems, and mutualistic relationships like pollination. Orchids are one of the most threatened plant families, yet the impact of invasive bees on their reproduction remains poorly understood. We conduct a global literature survey on the incidence of invasive honeybees (Apis mellifera) on orchid pollination, followed by a study case on Australian orchids. Our literature survey shows that Apis mellifera is the primary alien bee visiting orchids worldwide. However, in most cases, introduced honeybees do not deposit orchid pollen. We also test the extent to which introduced honeybees affect orchid pollination using Diuris brumalis and D. magnifica. Diuris brumalis shows higher fruit set and pollination in habitats with both native and invasive bees compared to habitats with only introduced bees. Male and female reproductive success in D. magnifica increases with native bee abundance, while conversely pollinator efficiency decreases with honeybee abundance and rises with habitat size. Our results suggest that introduced honeybees are likely involved in pollen removal but do not effectively deposit orchid pollen, acting as pollen wasters. However, Apis mellifera may still contribute to pollination of Diuris where native bees no longer exist. Given the global occurrence of introduced honeybees, we warn that certain orchids may suffer from pollen depletion by these invaders, especially in altered habitats with compromised pollination communities.

Managed honeybee hives negatively affect the reproduction of native plants in a dryland nature reserve

Abstract The honeybee, Apis mellifera, stands out for its positive image due to its contribution to crop pollination and honey production, which facilitated its widespread distribution. However, large apiaries resulting in high honeybee densities could increase pollination frequency while increasing competition for floral resources, ultimately affecting native plant fitness. We studied the impact of managed honeybee hives on pollination and reproductive success of native plants in Villavicencio Nature Reserve, Mendoza, Argentina. During the flowering peak, we studied pollination and reproduction of three native plant species (Larrea divaricata, L. cuneifolia and Zuccagnia punctata) near and far from the hives. We estimated pollen deposition on flower stigmas, pollen tubes developed in flower pistils, fruit set, seed set and seed viability. We found that the honeybee hives had a positive effect on the reproduction of the self‐compatible species, L. divaricata. For the self‐incompatible species, results differed among species: Hives had positive effects on the pollination and negative effects on the reproduction of L. cuneifolia, while they had negative effects on the reproduction of Z. punctata. Synthesis and applications. Beekeeping is increasingly turning to natural areas in search of better quality honey; however, increased honeybee abundance in the field could influence the reproduction of native plants. Our results show that the introduction of managed hives negatively affected the reproduction of self‐incompatible native plants. This result allows us to make several recommendations for conservation and management actions concerning beekeeping in natural areas, regarding the among‐year rotation of the location of hives, the number of hives per site, and the need to monitor the reproduction of self‐incompatible species.

Maintaining habitat diversity at small scales benefits wild bees and pollination services in mountain apple orchards

Abstract Landscape context influences wild bee abundance and diversity, alongside pollination‐related services. Growing evidence supports the positive effects of landscape heterogeneity on bee diversity and fruit production for pollination‐dependent crops in flatlands. However, little remains known about these relationships in mountainous environments where the landscape matrix surrounding crops is often more complex than in lowlands. We conducted our study in apple orchards in South Tyrol, an Alpine region in Italy, using pan‐traps, direct observations of visitation frequency and a pollinator exclusion experiment. We investigated the scale‐dependent effects of landscape heterogeneity and other parameters on wild bee assemblages and the related pollination service they provide at five spatial scales (radius 100–2000 m). We found that landscape heterogeneity positively affected the abundance and richness of wild bees, with the strongest effect at 500 m. We calculated a multidiversity index, reflecting the land‐use intensity based on the species richness of vascular plants, grasshoppers, butterflies, birds and bats. We identified a positive relationship between this multidiversity index and wild bee richness. Additionally, we found that visitation rate of wild bees was negatively affected by crop cover and that abundance of honeybees did not influence wild bee visitation rate or reproductive success. Finally, reproductive success was positively related to semi‐natural habitat cover. Landscape heterogeneity should be maintained in apple orchards to continue to reap the benefits of vital pollination‐related services. Diversification strategies should be implemented to promote habitat diversity at small scales, even in regions with more than 80% of (semi‐)natural habitats.

Understanding how environmental degradation, microclimate, and management shape honey production across different spatial scales.

Although the abundance, survival, and pollination performance of honeybees are sensitive to changes in habitat and climate conditions, the processes by which these effects are transmitted to honey production and interact with beekeeping management are not completely understood. Climate change, habitat degradation, and beekeeping management affect honey yields, and may also interact among themselves resulting in indirect effects across spatial scales. We conducted a 2-year, multi-scale study on Chiloe Island (northern Patagonia), where we evaluated the most relevant environmental and management drivers of honey produced by stationary beekeepers. We found that the effects of microclimate, habitat, and management variables changed with the spatial scale. Among the environmental variables, minimum temperature, and cover of the invasive shrub, gorse (Ulex europaeus) had the strongest detrimental impacts on honey production at spatial scales finer than 4km. Specialized beekeepers who adopted conventional beekeeping and had more mother colonies were more productive. Mean and minimum temperatures interacted with the percentage of mother colonies, urban cover, and beekeeping income. The gorse cover increased by the combination of high temperatures and the expansion of urban lands, while landscape attributes, such as Eucalyptus plantation cover, influenced beekeeping management. Results suggest that higher temperatures change the available forage or cause thermal stress to honeybees, while invasive shrubs are indicators of degraded habitats. Climate change and habitat degradation are two interrelated environmental phenomena whose effects on beekeeping can be mitigated through adaptive management and habitat restoration.

Landscape structure and farming management interacts to modulate pollination supply and crop production in blueberries

Abstract Pollination services are affected by landscape context, farming management and pollinator community structure, all of which impact flower visitation rates, pollen deposition and final production. We studied these processes in Argentina for highbush blueberry crops, which depend on pollinators to produce marketable yields. We studied how land cover and honeybee stocking influence the abundance of wild and managed pollinators in blueberry crops, using structural equation modelling to disentangle the cascading effects through which pollinators contribute to blueberry fruit number, size, nutritional content and overall yield. All pollinator functional groups responded to landscape changes at a spatial scale under 1000 m, and the significance or direction of the effects were modulated by the field‐level deployment of honeybee hives. Fruit diameter increased with pollen deposited, but decreased with honeybee abundance, which, had indirect effects on fruit acidity. Honeybees had a positive effect on the number of fruit produced by the plants and also benefited the overall yield (kg plant−1) through independent effects on both the quality and quantity components of fruit production. Synthesis and applications. Deployment of beehives in blueberry fields can buffer, but not compensate for the negative effects on honeybee abundance produced by surrounding large scale none‐flowering crops. Such compensation would require high‐quality beehives by monitoring their health and strength. The contribution of honeybees to crop production is not equal across production metrics. That is, higher abundance of honeybees increases the number of berries produced but at the cost of smaller and more acidic fruits, potentially reducing their market value. Growers must consider this trade‐off between fruit quantity and quality when actively managing honeybee abundance.

The importance of shrubland and local agroecological practices for pumpkin production in sub-Saharan smallholdings

Land-use and local field management affect pollinators, pest damage and ultimately crop yields. Agroecology is implemented as a sustainable alternative to conventional agricultural practices, but little is known about its potential for pollination and pest management. Sub-Saharan Africa is underrepresented in studies investigating the relative importance of pests and pollinators for crop productivity and how this might be influenced by surrounding landscapes or agroecological practices. In Malawi, we selected 24 smallholder farms differing in landscape-scale shrubland cover, implementation of manual pest removal as an indicator of an agroecological pest management practice, and the number of agroecological soil practices employed at the household level, such as mulching, intercropping and soil conservation tillage. We established pumpkin plots and assessed the abundance and richness of flower visitors and damage of flowers (florivory) caused by pest herbivores on flowers. Using a full-factorial hand pollination and exclusion experiment on each plot, we investigated the relative contribution of pollination and florivory to pumpkin yield. Increasing shrubland cover decreased honeybee abundance but increased the abundance and richness of non-honeybee visitors. Manual removal of herbivores considered to be pests reduced flower visitors, whereas more agroecological soil management practices increased flower visitors. Neither shrubland cover nor agroecological management affected florivory. Pollinator limitation, but not florivory, constrained pumpkin fruit set, and increasing visitor richness decreased the relative differences between hand- and animal-pollinated flowers. We recommend improved protection of shrubland habitats and increasing agroecological soil practices to promote pollinator richness on smallholder farms.

Diversity and Abundance of Insect Pollinators of Cucurbits at Mid-Hills of Meghalaya, India

The current research was carried out at the ICAR-Research Complex for the North Eastern Hill Region (NEH) in Umiam, Meghalaya to investigate the diversity and abundance of insect pollinators of cucurbits at mid-hills of Meghalaya. Ridge gourd, sponge guard, pumpkin, teasel gourd, chow-chow, bottle guard and cucumber were taken as a target crop to observe the data on diversity and abundance. Total twenty-five (25) pollinators were observed in different cucurbits belongs to order Hymenoptera, Diptera and Lepidoptera which represents that mid-hills of Meghalaya have rich pollinator fauna. Out of 25 insect pollinators 3 pollinators identified from ridge gourd, 6 from sponge gourd, 4 from pumpkin, 3 from bottle gourd, 4 from cucumber, 3 from chow-chow and 2 from teasel gourd. Efficient pollinator was nominated on the basis of their abundance. During investigation it was found that bumble bee emerged as the most abundant pollinator in ridge gourd, pumpkin and sponge gourd. In sponge gourd carpenter bee also showed almost equal abundance. Indian honey bee abundance was high in cucumber and in chow-chow. Among collected pollinators, hymenopterans were the abundant with 80% relative abundance. It is clear from the recorded observation that native bees are equally contributing in pollination service so conservation of these bees is also a demand of nature. Activity time period of pollinators on flowers guided the farmers to avoid pesticide spray during particular time period.

Local and landscape context affects bee communities in mixed fruit orchards in Southern Thailand

Abstract Bees play an important role by contributing to the pollination of a diverse range of crops and wild plants. However, bees are threatened by deforestation and habitat degradation caused by urbanization and agricultural intensification, which reduce floral and nesting resources. In this study, the effects of local (orchard size, flowering plant abundance and richness and floral abundance) and landscape factors (surrounding agricultural, forest and urban cover) on bee richness and abundance in mixed fruit orchards were determined from 28 mature orchards interspersed along a gradient of landscape complexity. Bees were observed for 15 min in 2 × 2 m plots. We categorized all bees into one of the three groups: (a) honey bees, (b) solitary bees and (c) stingless bees. Several local and landscape factors were found to influence bee richness and abundance. Honey bee abundance was positively affected by orchard size, whereas honey bee richness was not. Stingless bee richness and abundance were positively correlated with floral abundance. Forest cover within a 3‐km radius positively affected solitary bee richness. Solitary bee abundance was positively affected by forest cover within a 3‐km radius and negatively impacted by urban cover within a 1.5‐km radius. In our study area, small forest patches are found in abundance; thus, the high proportion of forest edge, relative to the forest interior, greatly supports solitary bee abundance and richness in this landscape. Moreover, most solitary bees are soil‐nesting species that may be excluded from environments that are converted from natural to anthropogenically developed areas. Recommendations to protect pollinators included conserving existing forest patches, especially forest margins; restoring forest patches within farmland landscapes; maintaining a diversity of herbs and grasses within mixed fruit orchards; establishing live fences composed of diverse plant species and retaining dead trees within farmland. For urban areas, augmenting floral resources in green spaces is suggested.

Honey bees (Apis mellifera) modify plant-pollinator network structure, but do not alter wild species' interactions.

Honey bees (Apis mellifera) are widely used for honey production and crop pollination, raising concern for wild pollinators, as honey bees may compete with wild pollinators for floral resources. The first sign of competition, before changes appear in wild pollinator abundance or diversity, may be changes to wild pollinator interactions with plants. Such changes for a community can be measured by looking at changes to metrics of resource use overlap in plant-pollinator interaction networks. Studies of honey bee effects on plant-pollinator networks have usually not distinguished whether honey bees alter wild pollinator interactions, or if they merely alter total network structure by adding their own interactions. To test this question, we experimentally introduced honey bees to a Canadian grassland and measured plant-pollinator interactions at varying distances from the introduced hives. We found that honey bees increased the network metrics of pollinator and plant functional complementarity and decreased interaction evenness. However, in networks constructed from just wild pollinator interactions, honey bee abundance did not affect any of the metrics calculated. Thus, all network structural changes to the full network (including honey bee interactions) were due only to honey bee-plant interactions, and not to honey bees causing changes in wild pollinator-plant interactions. Given widespread and increasing use of honey bees, it is important to establish whether they affect wild pollinator communities. Our results suggest that honey bees did not alter wild pollinator foraging patterns in this system, even in a year that was drier than the 20-year average.

Mason bees and honey bees synergistically enhance fruit set in sweet cherry orchards

AbstractMason bees (Osmia spp.) are efficient fruit tree pollinators that can be encouraged to occupy and breed in artificial nesting material. In sweet cherry orchards, they are occasionally used as an alternative managed pollinator as a replacement for or in addition to honey bees (Apis mellifera). Yet, the lack of practical guidelines on management practices, for example optimal stocking rates, for both mason bee nesting material and honey bees might compromise pollination service provision. In this study, we assessed the relationship between stocking rates (honey bee hives and mason bee nesting material) and the abundance of honey bees and mason bees in 17 sweet cherry (Prunus avium) orchards in Central Germany. We furthermore performed a pollination experiment to explore the interactive effect of mason bees and honey bees on sweet cherry fruit set. In the orchards, both honey bee and mason bee abundance increased with increasing stocking rates of hives or nesting material, respectively. Honey bee abundance increased linearly with stocking rates. In contrast, mason bee abundance asymptoted at 2–3 nesting boxes per ha, beyond which more boxes resulted in little increase in visitation rate. Our pollination experiment demonstrated that orchards were pollen limited, with only 28% of insect‐pollinated flowers setting fruit versus 39% of optimally hand‐pollinated flowers. Honey bees and mason bees enhanced sweet cherry fruit set, but only when both were present and not when either was present alone in an orchard. Our findings demonstrate that offering nesting material for mason bees and employing honey bee hives can enhance bee abundance in sweet cherry orchards. By increasing honey bee abundance in combination with enhanced mason bee abundance, farmers can substantially boost fruit set and potentially sweet cherry yield. To enhance pollination services, farmers should consider the benefits of increasing pollinator biodiversity as an immediate benefit to improve crop yields.

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.

Exploring relationships between time of day and pollinator activity in the context of pesticide use

Pesticide exposure can be harmful to insect pollinators and the ecosystem services they provide. As many pesticide guidelines warn against applying such products when pollinators are active, it is important to evaluate how pollinator activity changes with time of day to determine the most appropriate time to spray.We walked transects from sunrise to sunset in oilseed rape (Brassica napus L.) fields in Ireland to capture the abundance of honeybees, bumblebees, solitary bees, and hoverflies across daylight hours. We also recorded the activity of representative species from the three bee groups at their nests across similar time periods to compare with field observations.Peak pollinator abundance was in the mid-afternoon with fewer individuals in the early morning and late evening for all groups. At the nest we observed patterns of activity that broadly reflected field abundance but indicated that bees are active earlier and later than observed on the crop. However, there were differences between pollinator groups. Overall, honeybee and solitary bee abundance and activity were found to peak in the middle of the day, while bumblebee abundance and activity was more consistent throughout daylight hours. Hoverflies were relatively abundant in the morning and increased in number towards the late afternoon and early evening.Our results confirm current recommendations that pesticide application should be avoided in the middle of the day when pollinators are most active. However, the diversity of responses within and between pollinator groups to time of day should be accounted for when shaping guidelines, and clearly defining optimal pesticide application timings for end users is difficult and needs further consideration as it will vary between regions and crops. Further research should also explore how time impacts both pesticide efficacy and exposure of pollinators to residues post-application to allow full evaluation of how practical and beneficial timing of application may be when aiming to protect pollinators from pesticide exposure.

Within-bloom shift in abundance of a wild pollinator mediates pollen deposition rates to blueberry

Intra-seasonal variation in abiotic and biotic conditions can have profound consequences for pollinator community compositions and foraging movement, with flow-on effects upon pollination services. Yet, few studies have related such variations to pollination services in crop systems. In a cultivated highbush blueberry system with two primary pollinators — the managed European honey bee and a wild stingless bee species — we investigated how pollinator abundances, bee foraging behaviour, and con- and heterospecific stigmatic pollen loads changed over early, mid, and late blueberry blooming. Both con- and heterospecific stigmatic pollen loads declined following early bloom. This shift was associated with a decline in the abundance of stingless bees, whereas the abundance of honey bees only declined during late bloom. Simultaneously, honey bees were more likely to forage for blueberry pollen, and stigmatic pollen loads, relative to bee abundance, increased during late bloom. Although mixed pollen loads were common on pollinator bodies, especially on pollen foraging honey bees, heterospecific pollen deposition on blueberry stigmas was low. Given the similar effectiveness of honey bees and stingless bees as pollinators of blueberries, we contend that the observed seasonal variation in pollen deposition is likely caused by the decline in stingless bee abundances, as honey bees were not able to fully compensate for the loss of stingless bees during late bloom. Greater consideration of seasonal heterogeneity of pollinator abundance and behaviour, as part of pollination management plans, may aid in ensuring high pollination services throughout the entirety of crop bloom.