Farming practices influence wild pollinator populations on squash and pumpkin

Recent declines in managed honey bee, Apis mellifera L., colonies have increased interest in the current and potential contribution of wild bee populations to the pollination of agricultural crops. Because wild bees often live in agricultural fields, their population density and contribution to crop pollination may be influenced by farming practices, especially those used to reduce the populations of other insects. We took a census of pollinators of squash and pumpkin at 25 farms in Virginia, West Virginia, and Maryland to see whether pollinator abundance was related to farming practices. The main pollinators were Peponapis pruinosa Say; honey bees, and bumble bees (Bombus spp.). The squash bee was the most abundant pollinator on squash and pumpkin, occurring at 23 of 25 farms in population densities that were commonly several times higher than that of other pollinators. Squash bee density was related to tillage practices: no-tillage farms hosted three times as great a density of squash bees as tilled farms. Pollinator density was not related to pesticide use. Honey bee density on squash and pumpkin was not related to the presence of managed honey bee colonies on farms. Farms with colonies did not have more honey bees per flower than farms that did not keep honey bees, probably reflecting the lack of affinity of honey bees for these crops. Future research should examine the economic impacts of managing farms in ways that promote pollinators, particularly pollinators of crops that are not well served by managed honey bee colonies.     

Fidelity of Hymenoptera and Diptera pollinators in onion (Allium cepa L.) pollination

Onion (Allium cepa L.) is protandrous in nature and requires cross‐pollination to avoid inbreeding. The pollination potential of native bees (Hymenoptera) and true flies (Diptera) was assessed in the perspective of finding the best pollinators for onion cross‐pollination and seed multiplication. The community of pollinators was composed of four bee species and twelve true fly species. Episyrphus balteatus, Eupeodes sp., Musca domestica and Eristalinus aeneus were the most abundant pollinators. The maximum pollinator activity was observed from 12 to 24 days after opening of the flowers. The pollination effectiveness of tested bees (Apis dorsata and Apis florea) was greater than true flies (E. balteatus, Eupeodes sp., M. domestica, E. aeneus and Callihoridae sp.) in terms of Spears values.     

Experimental evidence that wildflower strips increase pollinator visits to crops

Wild bees provide a free and potentially diverse ecosystem service to farmers growing pollination‐dependent crops. While many crops benefit from insect pollination, soft fruit crops, including strawberries are highly dependent on this ecosystem service to produce viable fruit. However, as a result of intensive farming practices and declining pollinator populations, farmers are increasingly turning to commercially reared bees to ensure that crops are adequately pollinated throughout the season. Wildflower strips are a commonly used measure aimed at the conservation of wild pollinators. It has been suggested that commercial crops may also benefit from the presence of noncrop flowers; however, the efficacy and economic benefits of sowing flower strips for crops remain relatively unstudied. In a study system that utilizes both wild and commercial pollinators, we test whether wildflower strips increase the number of visits to adjacent commercial strawberry crops by pollinating insects. We quantified this by experimentally sowing wildflower strips approximately 20 meters away from the crop and recording the number of pollinator visits to crops with, and without, flower strips. Between June and August 2013, we walked 292 crop transects at six farms in Scotland, recording a total of 2826 pollinators. On average, the frequency of pollinator visits was 25% higher for crops with adjacent flower strips compared to those without, with a combination of wild and commercial bumblebees (Bombus spp.) accounting for 67% of all pollinators observed. This effect was independent of other confounding effects, such as the number of flowers on the crop, date, and temperature. Synthesis and applications. This study provides evidence that soft fruit farmers can increase the number of pollinators that visit their crops by sowing inexpensive flower seed mixes nearby. By investing in this management option, farmers have the potential to increase and sustain pollinator populations over time.     

Pollination efficiency of wild bees and hoverflies provided to oilseed rape

• 1 Declining numbers in honeybees and various wild bee species pose a threat to global pollination services. The identification and quantification of the pollination service provided by different taxa within the pollinator guild is a prerequisite for the successful establishment of nature conservation and crop management regimes.
• 2 Wild bees and hoverflies are considered to be valuable pollinators in agricultural and natural systems. Although some information on pollination efficiency of individual pollinator species is available, comparative studies of both taxa at different densities are rare. In the present study, the efficiency of the solitary mason bee Osmia rufa and two hoverfly species (Eristalis tenax and Episyrphus balteatus) as pollinators of oilseed rape Brassica napus was examined in a standardized caged plant breeding regime. Honeybee Apis mellifera colonies were used as a reference pollinator taxon.
• 3 Yield parameters responded differently to pollinator density and identity. Fruit set and number of seeds per pod increased with increasing pollinator density, although these were stronger in the mason bee than the hoverfly treatment. Weight per 1000 seeds did not respond to any pollinator treatment, indicating that seed quality was not affected. Oilseed rape yield in the highest tested densities of both pollinator taxa resulted in yield values close to the efficiency of small honeybee colonies.
• 4 Hoverflies required approximately five‐fold densities of the red mason bees to reach a similar fruit set and yield. Thus, mason bees are more efficient in plant breeding and managed pollination systems. Both natural pollinator taxa, however, are of potential value in open and closed crop production systems.

     

Seasonal complementary in pollinators of soft-fruit crops

Understanding the relative contributions of wild and managed pollinators, and the functional contributions made by a diverse pollinator community, is essential to the maintenance of yields in the 75% of our crops that benefit from insect pollination. We describe a field study and pollinator exclusion experiments conducted on two soft-fruit crops in a system with both wild and managed pollinators. We test whether fruit quality and quantity is limited by pollination, and whether different pollinating insects respond differently to varying weather conditions. Both strawberries and raspberries produced fewer marketable fruits when insects were excluded, demonstrating dependence on insect pollinators. Raspberries had a short flowering season which coincided with peak abundance of bees, and attracted many bees per flower. In contrast, strawberries had a much longer flowering season and appeared to be much less attractive to pollinators, so that ensuring adequate pollination is likely to be more challenging. The proportion of high-quality strawberries was positively related to pollinator abundance, suggesting that yield was limited by inadequate pollination on some farms. The relative abundance of different pollinator taxa visiting strawberries changed markedly through the season, demonstrating seasonal complementarity. Insect visitors responded differently to changing weather conditions suggesting that diversity can reduce the risk of pollination service shortfalls. For example, flies visited the crop flowers in poor weather and at the end of the flowering season when other pollinators were scarce, and so may provide a unique functional contribution. Understanding how differences between pollinator groups can enhance pollination services to crops strengthens the case for multiple species management. We provide evidence for the link between increased diversity and function in real crop systems, highlighting the risks of replacing all pollinators with managed alternatives.     

Bumble bee abundance and richness improves honey bee pollination behaviour in sweet cherry

Pollination service in agricultural crops increases significantly with pollinator diversity and wild pollinator abundance. Differences in the foraging behaviour of pollinating insects are one of the reasons why pollinator diversity and abundance enhances crop pollination. Here, we focused on the foraging behaviour of honey bees and bumble bees in sweet cherry orchards. In addition, we studied the influence of bee diversity and abundance on the foraging behaviour of honey bees and bumble bees. Honey bees were found to visit fewer flowers than bumble bees. Bumble bees also showed a higher probability of changing trees between rows than honey bees. Both visitation rate and probability of row changes of honey bees increased with bumble bee diversity and with bumble bee abundance. We also found that the probability of row changes of honey bees increased with increasing bumble bee abundance. These effects of bumble bee richness and abundance on the pollination behaviour of honey bees can improve the pollination performance of honey bees in crops that depend on cross pollination. Our results highlight the higher pollination performance of bumble bees and the facilitative effect of wild pollinators to crop pollination.     

Species Distribution Models for Crop Pollination: A Modelling Framework Applied to Great Britain

Insect pollination benefits over three quarters of the world''s major crops. There is growing concern that observed declines in pollinators may impact on production and revenues from animal pollinated crops. Knowing the distribution of pollinators is therefore crucial for estimating their availability to pollinate crops; however, in general, we have an incomplete knowledge of where these pollinators occur. We propose a method to predict geographical patterns of pollination service to crops, novel in two elements: the use of pollinator records rather than expert knowledge to predict pollinator occurrence, and the inclusion of the managed pollinator supply. We integrated a maximum entropy species distribution model (SDM) with an existing pollination service model (PSM) to derive the availability of pollinators for crop pollination. We used nation-wide records of wild and managed pollinators (honey bees) as well as agricultural data from Great Britain. We first calibrated the SDM on a representative sample of bee and hoverfly crop pollinator species, evaluating the effects of different settings on model performance and on its capacity to identify the most important predictors. The importance of the different predictors was better resolved by SDM derived from simpler functions, with consistent results for bees and hoverflies. We then used the species distributions from the calibrated model to predict pollination service of wild and managed pollinators, using field beans as a test case. The PSM allowed us to spatially characterize the contribution of wild and managed pollinators and also identify areas potentially vulnerable to low pollination service provision, which can help direct local scale interventions. This approach can be extended to investigate geographical mismatches between crop pollination demand and the availability of pollinators, resulting from environmental change or policy scenarios.     

Managed bumble bees increase flower visitation but not fruit weight in polytunnel strawberry crops

Animal-mediated pollination is essential for the production and quality of fruits and seeds of many crops consumed by humans. However, crop pollination services might be compromised when wild pollinators are scarce. Managed pollinators are commonly used in crops to supplement such services with the assumption that they will enhance crop yield. However, information on the spatiotemporal pollinator-dependence of crops is still limited. We assessed the contribution of commercial bumble bee colonies compared to the available pollinator community on strawberry (‘Fortuna’ variety) flower visitation and strawberry quality across a landscape gradient of agricultural intensification (i.e. polytunnel berry crop cover). We used colonies of bumble bees in winter and in spring, i.e. when few and most wild pollinators are in their flight period, respectively. The placement of colonies increased visits of bumble bees to strawberry flowers, especially in winter. The use of bumble bee colonies did not affect flower visitation by other insects, mainly honey bees, hoverflies and other Diptera. Flower visitation by both honey bees and wild insects did not vary between seasons and was unrelated to the landscape gradient of berry crop cover. Strawberries were of the highest quality (i.e. weight) when insect-mediated pollination was allowed, and their quality was positively related to wild flower visitors in winter but not in spring. However, increased visits to strawberry flowers by managed bumble bees and honey bees had no effect on strawberry weight. Our results suggest that the pollination services producing high quality strawberry fruits are provided by the flower visitor community present in the study region without the need to use managed bumble bees.     

Solitary invasive orchid bee outperforms co-occurring native bees to promote fruit set of an invasive Solanum

Our understanding of the effects of introduced invasive pollinators on plants has been exclusively drawn from studies on introduced social bees. One might expect, however, that the impacts of introduced solitary bees, with much lower population densities and fewer foragers, would be small. Yet little is known about the potential effects of naturalized solitary bees on the environment. We took advantage of the recent naturalization of an orchid bee, Euglossa viridissima, in southern Florida to study the effects of this solitary bee on reproduction of Solanum torvum, an invasive shrub. Flowers of S. torvum require specialized buzz pollination. Through timed floral visitor watches and two pollination treatments (control and pollen supplementation) at three forest edge and three open area sites, we found that the fruit set of S. torvum was pollen limited at the open sites where the native bees dominate, but was not pollen limited at the forest sites where the invasive orchid bees dominate. The orchid bee’s pollination efficiency was nearly double that of the native halictid bees, and was also slightly higher than that of the native carpenter bee. Experiments using small and large mesh cages (to deny or allow E. viridissima access, respectively) at one forest site indicated that when the orchid bee was excluded, the flowers set one-quarter as many fruit as when the bee was allowed access. The orchid bee was the most important pollinator of the weed at the forest sites, which could pose additional challenges to the management of this weed in the fragmented, endangered tropical hardwood forests in the region. This specialized invasive mutualism may promote populations of both the orchid bee and this noxious weed. Invasive solitary bees, particularly species that are specialized pollinators, appear to have more importance than has previously been recognized. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Pollinator Shift and Reproductive Performance of the Qinghai–Tibetan Plateau Endemic and Endangered Swertia przewalskii (Gentianaceae)

Reproductive failure results in many plant species becoming endangered. However, little is known of how and to what extent pollinator shifts affect reproductive performance of endangered species as a result of the artificial introduction of alien insects. In this study we examined breeding systems, visitor species, visiting frequency and seed set coefficients of Swertia przewalskii in two years that had different dominant pollinator species (native vs. alien). Flowers of this species were protandrous and herkogamous and insects were needed for the production of seeds. The stigmatic receptivity of this species was shorter than for other gentians. No significant difference in seed set coefficient was found for hand-pollinated plants between the two years, indicating that pollinator shift only had a minor effect on this plant’s breeding system. The commonest pollinators in 2002 were native bumblebees, alien honeybees and occasional solitary bees, however, only alien honeybees were observed in 2004. The flower visitation rate in both years was relatively high, although the total visit frequency decreased significantly in 2004. The control flowers without any treatment produced significantly fewer seed sets in 2004 than in 2002. In the past decade the seed production of this species may have partly decreased due to pollination by alien honeybees, however, we suggest that they might have acted as alternative pollinators ensuring seed production of S. przewalskii when native pollinators were unavailable. The main reason that this plant is endangered is probably the result of habitat destruction, but changes in land use, namely intensified agricultural practice and unfavorable animal husbandry have also contributed to its decline. We recommend that in-situ conservation, including the establishment of a protected area, is the best way to preserve this species effectively.     

Landscape effects on crop pollination services: are there general patterns?

Pollination by bees and other animals increases the size, quality, or stability of harvests for 70% of leading global crops. Because native species pollinate many of these crops effectively, conserving habitats for wild pollinators within agricultural landscapes can help maintain pollination services. Using hierarchical Bayesian techniques, we synthesize the results of 23 studies – representing 16 crops on five continents – to estimate the general relationship between pollination services and distance from natural or semi-natural habitats. We find strong exponential declines in both pollinator richness and native visitation rate. Visitation rate declines more steeply, dropping to half of its maximum at 0.6 km from natural habitat, compared to 1.5 km for richness. Evidence of general decline in fruit and seed set – variables that directly affect yields – is less clear. Visitation rate drops more steeply in tropical compared with temperate regions, and slightly more steeply for social compared with solitary bees. Tropical crops pollinated primarily by social bees may therefore be most susceptible to pollination failure from habitat loss. Quantifying these general relationships can help predict consequences of land use change on pollinator communities and crop productivity, and can inform landscape conservation efforts that balance the needs of native species and people.     

Diurnal effectiveness of pollination by bees and flies in agricultural Brassica rapa: Implications for ecosystem resilience

Bees are known to provide pollination services to a wide range of crops, yet flies are rarely included in estimates of function. As bees and flies differ markedly in their life history characteristics and resource needs, they may be active and hence provide pollination services at different times of the day. Here, we explore the differences in bee and fly diurnal activity patterns and how this may impact upon pollination services provided to Brassica rapa, a mass-flowering crop. We observed pollinators at two-hourly intervals from 6:00 to 20:00 h in twelve fields in New Zealand in 2004–2005. Overall, bees were most active in the middle of the day and were more effective pollinators than flies, driven primarily by the high pollinator efficiency of Apis mellifera and Bombus terrestris. Some fly taxa however, visited flowers early and late in the day when there were few bees. The results of this study demonstrate that fine-scale temporal dynamics and the spatial distribution of crop pollinators may directly affect the quantity of pollination services. The maintenance of biodiversity in agro-ecosystems may therefore be critical to ensure pollinator taxa are available under a range of environmental conditions.     

Crop management affects pollinator attractiveness and visitation in oilseed rape

Ecological intensification of agriculture implies managing ecological processes to improve performance of agricultural systems. However, impacts on relevant ecological functions such as insect pollination from other crop management factors are poorly explored. Pest insects and crop resources such as water availability can directly affect crop yields, but it is unknown if there are indirect effects through effects on insect pollination. With a factorial experiment, we examined how irrigation and control of pollen beetles affected crop attractiveness and pollinator visitation in an open-pollinated spring oilseed rape cultivar. We studied how irrigation and pest control modified the production of flowers and nectar in oilseed rape, and if this in turn affected the flower-visitation of honey bees and bumble bees. Pest control increased the number of oilseed rape flowers by 69%, and the amount of nectar per flower with 36%, but for the latter only in non-irrigated plots. Furthermore, we found higher pollinator densities in plots with reduced pollen beetle densities. Pest control also reduced the number of non-legitimate flower visits, suggesting higher pollination efficiency in plots with reduced pollen beetle densities. We show that crop management affects the value of mass-flowering crops as a resource for pollinating insects. Development of pest control tools that are harmless to pollinators could increase the value of flowering crops as food resources for pollinating insects.     

The effect of wild radish floral morphology on pollination efficiency by four taxa of pollinators

The effects of floral morphology on rates of pollen removal and deposition by different pollinators in generalist plant species are not well known. We studied pollination dynamics in wild radish, Raphanus raphanistrum, a plant visited by four groups of pollinators: honey bees, small native bees, butterflies, and syrphyd flies. The effects of anther position and other factors on pollen removal during single visits by all four pollinator taxa were measured. Flowers with high anther exsertion (i.e., anthers placed higher above the opening of the corolla tube) tended to have the highest numbers of pollen grains removed, but this effect was strongest for honey bees and butterflies. For all pollinator taxa, pollen removal increased with the number of pollen grains available on a flower and whowed a positive, decelerating relationship with the duration of the visit. The effects of stigma position and other factors on pollen deposition during single visits by honey bees and butterflies were also studied. The nectar-feeding butterflies had a higher pollination efficiency (percentage of pollen grains removed from anthers that were subsequently deposited on a stigma) than the nectar- and pollen-feeding honey bees. Flowers with intermediate stigma exsertion had the highest numbers of pollen grains deposited on their stigmas by butterflies, but stigma exsertion had no effect on deposition by honey bees. For both butterflies and honey bees, pollen deposition on the recipient flower increased with the amount of pollen removed from the donor flower, and there was a positive, decelerating relationship between deposition and time spent at the flower; these results are analogous to those for pollen removal. The effects of anther and stigma exsertion on pollen removal and denosition did not fit predictions based on patterns of floral correlations, but results for morphology, pollen availability, time spent per visit, and pollinator efficiency are in broad agreement with previous studies, suggesting the possible emergence of some general rules of pollen transfer.     

Reproductive ecology of tropical forest trees in logged and fragmented habitats in Thailand and Costa Rica

Invertebrates mediate several important ecological processes, including pollination and seed predation, and events that affect invertebrate diversity or behaviour can potentially disrupt forest regeneration processes. This study investigates the impact of logging in Thailand and forest fragmentation in Costa Rica on the pollination and seed production of two self-incompatible forest trees. Logging in a dry deciduous dipterocarp forest in Thailand resulted in reduced densities of the common dipterocarp treeShorea siamensis and variably isolated individual trees. The number of flower visits to S. siamensis by pollinating Trigona bees was not affected by logging disturbance. However, pollinators did spend longer periods of time foraging in the canopies of isolated trees which were more prevalent in logged areas where tree density had been reduced. Consequently, at the logged site few cross-pollinations were effected and fruit set of S. siamensis was considerably lower than at nearby unlogged sites where distances between flowering conspecifics were smaller. Reduced fruit set has long-term implications for the recovery of S. siamensis populations in disturbed areas, and local population genetic structure is likely to be affected as reduced outcrossing rates among trees in disturbed regions results in relatively inbred seed. In Costa Rica forest fragmentation has restricted the once widespread tree Anacardium excelsum to forest patches located in an agriculturally-dominated landscape. As with S. siamensis, the abundance of pollinators, also Trigona bees, in the canopies of A. excelsum was largely unaffected by fragment size. Nevertheless, pollination success and seed production was positively correlated with fragment size. We propose that small bees rarely move between forest fragments and gene exchange through pollination occurs predominantly among trees within fragments and, together with likely low genetic variability in small fragments, that this contributes to the observed reduced fertilisation and seed set of A. excelsum. Thus increased tree isolation tree through selective logging or habitat fragmentation by forest clearance can result in reduced seed set due to changes in the foraging patterns of poorly mobile pollinators. Even if population sizes of the pollinators are maintained following environmental perturbation, this study shows that disturbance may disrupt pollination processes through changes in pollinator foraging behaviour. More attention needs to be focussed on changes in the behaviour of species involved in key ecological interactions following disturbance events in tropical forests.     

Integrated crop pollination to buffer spatial and temporal variability in pollinator activity

Insect pollination improves the yield and quality of many crops, yet there is increasing evidence of insufficient insect pollinators limiting crop production. Effective Integrated Crop Pollination (ICP) involves adaptable, targeted and cost-effective management of crop pollination and encourages the use of both wild and managed pollinators where appropriate. In this study we investigate how the addition of honeybee hives affects the community of insects visiting oilseed rape, and if hive number and location affect pollinator foraging and oilseed rape pollination in order to provide evidence for effective ICP. We found that introducing hives increased overall flower visitor numbers and altered the pollinator community, which became dominated by honeybees. Furthermore a greater number of hives did not increase bee numbers significantly but did result in honeybees foraging further into fields. The timing of surveys and proximity to the field edge influenced different pollinators in different ways and represents an example of spatial and temporal complementarity. For example dipteran flower visitor numbers declined away from the field edge whereas honeybees peaked at intermediate distances into the field. Furthermore, no significant effects of survey round on wild bees overall was observed but honeybee numbers were relatively lower during peak flowering and dipteran abundance was greater in later survey rounds. Thus combining diverse wild pollinators and managed species for crop pollination buffers spatial and temporal variation in flower visitation. However we found no effect of insect pollination on seed set or yield of oilseed rape in our trial, highlighting the critical need to understand crop demand for insect pollination before investments are made in managing pollination services.     

Mass‐flowering crops dilute pollinator abundance in agricultural landscapes across Europe

Mass‐flowering crops (MFCs) are increasingly cultivated and might influence pollinator communities in MFC fields and nearby semi‐natural habitats (SNHs). Across six European regions and 2 years, we assessed how landscape‐scale cover of MFCs affected pollinator densities in 408 MFC fields and adjacent SNHs. In MFC fields, densities of bumblebees, solitary bees, managed honeybees and hoverflies were negatively related to the cover of MFCs in the landscape. In SNHs, densities of bumblebees declined with increasing cover of MFCs but densities of honeybees increased. The densities of all pollinators were generally unrelated to the cover of SNHs in the landscape. Although MFC fields apparently attracted pollinators from SNHs, in landscapes with large areas of MFCs they became diluted. The resulting lower densities might negatively affect yields of pollinator‐dependent crops and the reproductive success of wild plants. An expansion of MFCs needs to be accompanied by pollinator‐supporting practices in agricultural landscapes.     

Facial area and hairiness of pollinators visiting semi-natural grassland wild plants predict their facial pollen load

1. Consequences of a decline in pollination function in semi-natural ecosystems are largely unknown due to variability in pollinator effectiveness, that is, their contribution to pollen deposition alone. While pollination effectiveness has been shown to be related to body size and hairiness of pollinators for some crops, studies encompassing a wide diversity of pollinators interacting with wild plant communities are lacking. 2. Thus, the relationships between pollen load, which is a measurement of pollen transport ability and a proxy of pollinator effectiveness, and morphological traits of pollinators sampled in 16 grasslands in Moselle, France, were investigated. The area, hairiness, and pollen load of each pollinator's face were measured for 658 individuals from 127 bee and fly species interacting with 36 wild plant species. Pollinator dry mass was also measured on 543 individuals from 109 species. 3. Dry body mass and facial area of pollinators were positively linked. This study highlights that bees transported significantly more pollen grains on their face than flies. Furthermore, bees' faces were larger and hairier. We also found that pollinators' facial pollen load increased with facial area and hairiness when we considered all pollinators. However, hairiness is not significant within pollinator group (bees or flies), mirroring a potential phylogenetic signal. 4. Hence, this study shows a wide diversity of pollinator and plant species in which larger and hairier pollinators may transport more pollen grains, at least on their face. However, future studies involving other pollinator body parts are needed to generalise these relationships.     

Pollination ecology and breeding system of the very narrow coastal endemic Seseli farrenyi (Apiaceae). Effects of population fragmentation

The reproductive biology of Seseli farrenyi (Apiaceae), a very narrow endemic to Cape Creus (Catalonia, Spain), including flowering timing patterns, quantity and quality of pollination services (type and frequency of pollinators, pollen carryover, pollen deposition on stigmas and reproductive success measured as fruit set), and breeding system was studied. Given the decline of population size detected in the last twenty years, we also analyzed the effects of fragmentation on pollination mechanisms. Protandry along with strong synchrony of floral development within umbels and sequential inflorescence emission within individual stalks, produces sexual phase alternation that promotes a strong outcrossing despite its non-specific pollination system and its (at least partial) self-compatibility. This pronounced xenogamy is supported by results of the insect exclusion test, hand-pollination experiments, and high P/O ratio. S. farrenyi flowers received visits from at least 28 species of insects, including wasps, small bees, ants, flies, syrphid flies, beetles and stink bugs, with different pollen carry-overs. Heterospecific pollen on stigmas decreased notably during the season (50% to 2.5%), averaging 12%. In the small population the stigmatic pollen loads and seed set decreased, but there was no effect of pollinator visitation rates. It was more affected by the composition of pollinators and their efficiency. The wind had a considerable effect on the plant. Some conservation measures are proposed.     

Floral resource pulse decreases bumble bee foraging trip duration in central Wisconsin agroecosystem

1. Resource pulses, narrow periods of high resource availability, can elicit strong behavioural responses across diverse taxa. Mass‐flowering agricultural crops are an example of a resource pulse that insect pollinators exploit. However, the underlying mechanism behind changes in pollinator behaviour associated with mass‐flowering crops is still relatively unexplored. 2. The present study quantified the behavioural response of bumble bees, an important wild pollinator, to commercial cranberry bloom, an important mass‐flowering crop in Wisconsin, U.S.A. Over a 2‐year period, foraging trip duration was measured using radio frequency identification at 14 farms situated across landscape contexts, ranging from high to low natural area (woodland amount). Using transect surveys, floral resource abundance at a landscape scale was estimated. 3. It was found that bumble bees were highly sensitive to temporal changes in landscape‐level resource abundance associated with the onset of cranberry bloom, during which they decreased foraging trip duration by 22% and increased the number of foraging trips during bloom by 24% on average relative to the period before and after bloom. This phenomenon was consistent across colonies, individual bees, and landscape contexts, despite a higher abundance of flowers in low woodland landscapes. Bumble bee colonies growing in low‐ and high‐woodland landscapes exhibited a similar performance. 4. As mass‐flowering crops are probably a factor influencing bumble bee foraging behaviour in agricultural regions, investigations should continue into how variable resource landscapes, particularly those offering resource pulses, affect wild pollinators and the pollination services they provide.