Larger bees facilitate the deposition of oilseed rape pollen (Brassica napus L.)

Oilseed rape is the third-largest source of vegetable oil and the second-largest source of protein meal in the world. Pollinators are vital in the production of oilseed rape. However, pollination efficiency could be influenced by the morphology and foraging behaviors of pollinators. To evaluate the effect of pollinator size and foraging behavior on pollination efficiency, the intertegular distances (ITDs) of five bumble bees (Bombus pyrosoma, B. lantschouensis, B. melanurus, B. sichelii and B. sibiricus) and two honey bees (Apis mellifera and A. cerana) were evaluated. Their foraging activities and single visit depositions (SVDs) on oilseed rape were observed and counted. The ITDs of bumble bees were significantly larger than honey bees (P < 0.05). The single-visit duration of A. mellifera (2.43 ± 0.06 s) was significantly longer than other bees (P < 0.05). The interval time of the A. cerana was longer than other bees (P < 0.05). Larger bees tended to deposit more pollen on stigmas at each visit than smaller bees. The interspecific ITD of bees had a positive effect on SVD (P < 0.001). There was no correlation between ITD and SVD among individuals of the same species. In conclusion, the size of bees had a positive impact on pollination efficiency. Bees with a greater ITD deposited substantially more pollen and had a significantly shorter interval between flowers. Understanding the foraging behavior and pollination efficiency of these bee species and developing habitats to support them should enable growers to achieve resilient production.     

Bee visitation rates to trees of Prockia crucis differing in flower number

Summary Annual flower production ranged over four orders of magnitude among individuals of the tropical tree Prockia crucis (Flacourtiaceae), but the number of visits per flower by bees did not increase with flower number. In a population in Jalisco, México, the trees flower for about one week each year, offering only pollen to the bees (mostly solitary species). In a small group of trees, the number of visits per flower was less on trees with greater flower production but in a large group visitation did not vary between trees. Pollen flow probably was not directed from large to small trees or vice versa, because the number of flowers per tree did not determine the schedule of visits. The ratio of pollinators to pollen thieves decreased rapidly through the day, while individuals of both groups foraged more rapidly. Most bee species were rare, and only a small subset of medium-sized to large bees were effective pollinators. Large and small groups of trees differed in the relationship between individual flower crop and abundance and diversity of both pollinators and thieves.     

Sources of variation in pollinator contribution within a guild: the effects of plant and pollinator factors

Among plants visited by many pollinator species, the relative contribution of each pollinator to plant reproduction is determined by variation in both pollinator and plant traits. Here we evaluate how pollinator movement among plants, apparent pollen carryover, ovule number, resource limitation of seed set, and pollen output affect variation in contribution of individual pollinator species to seed set in Lithophragma parviflorum (Saxifragaceae), a species visited by a broad spectrum of visitors, including beeflies, bees and a moth species. A previous study demonstrated differences among visitor species in their single-visit pollination efficacy but did not evaluate how differences in visitation patterns and pollen carryover affect pollinator efficacy. Incorporation of differential visitation patterns and pollen carryover effects —commonly cited as potentially important in evaluating pollinator guilds — had minor effects (0–0.6% change) on the estimates of relative contribution based on visit frequency and single-visit efficacy alone. Beeflies visited significantly more flowers per inflorescence than the bees and the moth. Seed set remained virtually constant during the first three visited flowers for beeflies and larger bees, indicating that apparent pollen carryover did not reduce per-visit efficacy of these taxa. In contrast, Greya moth visits showed a decrease in seed set by 55.4% and the smaller bees by 45.4% from first to second flower. The larger carryover effects in smaller bees and Greya were diminished in importance by their small overall contribution to seed set. Three variable plant traits may affect seed set: ovule number, resource limitation on seed maturation, and pollen output. Ovule number per flower declined strongly with later position within inflorescences. Numbers were much higher in first-year greenhouse-grown plants than in field populations, and differences increased during 3 years of study. Mean pollen count by position varied 7-fold among flowers; it paralleled ovule number variation, resulting in a relatively stable pollen:ovule ratio. Resource limitation of seed set increased strongly with later flowering, with seed set in hand-pollinated flowers ranging from 66% in early flowers to 0% in the last two flowers of all plants. Variation in ovule number and resource limitation of seed maturation jointly had a strong effect on the number of seeds per flower. Visitation to early flowers had the potential to cause more seed set than visitation to later flowers. Overall, the most important sources of variation to seed production contribution were differences among pollinators in abundance and absolute efficacy (ovules fertilized on a single visit) and potentially differential phenology among visitor species. These effects are likely to vary among populations and years.     

Honey bee handling behaviour on the papilionate flower of Robinia pseudoacacia L.

Papilionate flowers, such as those of Robinia pseudoacacia L., show tripping mechanisms that prevent pollen release: only those bees which apply the right force on petals induce pollen to be deposited on their bodies. Apis mellifera is considered a poor visitor of such flowers, since individuals are usually too weak to trip the mechanism. Despite this, the honey bee pays frequent visits to flowers of R. pseudoacacia and produces a much appreciated unifloral honey. We investigated how bees manipulate R. pseudoacacia flowers, whether they contact the plant’s reproductive core and if there is any appreciable difference related to the manipulation of individual flowers. Honey bees showed two strategies for resource collection, namely legitimate visits and robberies. Legitimate visits were more frequent and about 63 % entailed contact with the flower’s reproductive core. We distinguished two behaviours, one to achieve successful positioning on the flower and the other for nectar intake. These behaviours were clearly perceptible and described by different curves of time frequency distribution. From the beginning to the end of anthesis, flowers were classified into four types on the basis of their morphological and phenological traits. Positioning time differed significantly depending on the flower type, with less time needed for more ageing flowers. Time spent in nectar intake was instead highly variable and independent of flower ageing. Selecting the right flower type would appear to lead to obtaining the R. pseudoacacia reward, overcoming species-specific physical inability. Moreover, the role of honey bees as pollinators of R. pseudoacacia is considered. Finally, the relations between petal characteristics and strength needed to trip the mechanism in papilionate flowers is also discussed in the light of nectar foragers.     

GM risk assessment: Pollen carriage from Brassica napus to B. rapa varies widely between pollinators

Characterizing insect pollen carriage between closely related plant species is especially challenging where source species possess morphologically identical pollen and share many pollinators in common. Here, we use an SNP-based assay using the plant DNA barcoding locus matK to characterize pollen carriage between cultivated Brassica napus and wild Brassica rapa in three sites across southern England. The assay differentiated B. napus and B. rapa pollen carried by honey bees (Apis melifera), bumblebees (Bombus spp.), mining bees (Andrena spp.) and hoverflies (Syrphidae) captured on B. napus plants 1–2 m from wild B. rapa, and on B. rapa plants at various distances from the crop . Apis individuals foraging on B. rapa and carrying B. napus pollen were rarely found beyond 10 m from the crop. However, Bombus and Andrena individuals captured on B. rapa occasionally carried crop pollen up to 300 m from the source field. Hoverflies carried less pollen overall but featured high proportions of B. napus pollen even at the most distant capture points. We predict that different pollinator species will evoke markedly different patterns of interspecific hybrid formation. We conclude that more exhaustive surveys of this kind will help parameterize future mechanistic models to predict the distribution of hybrids between Genetically Modified B. napus and B. rapa on a landscape scale.     

Insights from measuring pollen deposition: quantifying the pre-eminence of bees as flower visitors and effective pollinators

Using our accumulated datasets from Kenyan savanna, Mediterranean garigue, UK gardens and heathland, involving 76 plants from 30 families, we present detailed data to quantify the superiority of bees as pollinators of most flowering plants when compared with other flower visitors. Bees provided the majority of visits to study species at all sites, and 33 of the 76 plants received more than 90% of their visits from bees. Furthermore, pollen deposition onto stigmas from single-visit events (SVD, a measure of pollination effectiveness) was significantly higher for bees than non-bees at all the four sites where a major proportion of the flora was sampled. Solitary bees, and also bumblebees in temperate habitats, were the best potential pollinators for most plants in this respect, and significantly out-performed honeybees. Only a few plants were well served by bombyliid flies, and fewer again by larger hoverflies, butterflies, or solitary wasps. Bees also achieved better matches of their visit timing to peak pollen availability (measured indirectly as peak SVD), and made much shorter visits to flowers than did non-bees, permitting a substantially greater visit frequency. Additionally, they deposited significantly lower levels of potentially deleterious heterospecific pollen on stigmas in heathland and Mediterranean garigue, though not in the UK garden with densely clustered high-diversity flowering, or in the Kenyan savanna site with particularly dispersed flowering patches and some specialist non-bee flowers. Our data provide a novel and quantified characterisation of the specific advantages of bees as flower visitors, and underline the need to conserve diverse bee communities.     

Locomotion and the pollen hoarding behavioral syndrome of the honeybee (<Emphasis Type="Italic">Apis mellifera</Emphasis> L.)

Honeybees selected for the colony level phenotype of storing large quantities of pollen (pollen hoarding) in the nest exhibit greater walking activity than those selected against pollen hoarding. In this study, we use a simple walking assay to demonstrate that walking activity increases with the proportion of high pollen-hoarding alleles in pure and backcrossed strains of bees (high-strain bees > offspring generated from a high backcross > offspring generated from a low backcross > low-strain bees). The trait is heritable but is not associated with markers linked to three quantitative trait loci (QTL) mapped for their effects on pollen hoarding with demonstrated pleiotropic effects on pollen and nectar foraging and learning behavior. However, locomotion in non-selected bees is correlated with responsiveness to sucrose, a trait that correlates with foraging and learning behavior. We propose that pollen-hoarding behavior involves a syndrome of behavioral traits with complex genetic and regulatory architectures that span sensory sensitivity, foraging behavior, and learning. We propose that locomotor activity is the component of this syndrome and reflects the early maturation of the bees that become pollen foragers.     

BUMBLE BEE POLLINATION AND FLORAL MORPHOLOGY: FACTORS INFLUENCING POLLEN DISPERSAL IN THE ALPINE SKY PILOT,POLEMONIUM VISCOSUM (POLEMONIACEAE)

Pollen dispersal success in entomophilous plants is influenced by the amount of pollen produced per flower, the fraction of pollen that is exported to other flowers during a pollinator visit, visitation frequency, and the complementarity between pollen donor and recipients. For bumble bee-pollinated Polemonium viscosum the first three determinants of male function are correlated with morphometric floral traits. Pollen production is positively related to corolla and style length, whereas pollen removal per visit by bumble bee pollinators is a positive function of corolla flare. Larger-flowered plants receive more bumble bee visits than small-flowered individuals. We found no evidence of tradeoffs between pollen export efficiency and per visit accumulation of outcross pollen; each was influenced by unique aspects of flower morphology. Individual queen bumble bees of the principal pollinator species, Bombus kirbyellus, were similar in male, female, and absolute measures of pollination effectiveness. An estimated 2.9% of the pollen that bumble bees removed from flowers during a foraging bout was, on average, deposited on stigmas of compatible recipients. Significant plant-to-plant differences in pollen production, pollen export per visit, and outcross pollen receipt were found for co-occurring individuals of P. viscosum indicating that variation in these fitness related traits can be seen by pollinator-mediated selection.     

Low legitimate pollen flow in distylic Turnera hermannioides (Passifloraceae) and its consequences on fruit and seed set

Turnera hermannioides is a ruderal distylic subshrub, native to NE-Brazil. In the Catimbau National Park, situated within the semi-arid Caatinga region, we studied the pollination ecology of this species, emphasizing (1) effective pollinators; (2) characteristics of short- and long-styled flowers; (3) intra- and intermorph pollen flow; and (4) fruit and seed set. Short and long-styled morphs differ in pollen size and ornamentation, stigmatic surface, style and stamen length and nectar production. The flowers are obligate intermorphic outcrossers and depend on animals for pollination. The flowers of T. hermannioides attracted insect visitors of 25 species, among them butterflies, beetles, but mainly bees. Polylectic bees, such as Apis mellifera, stingless bees, and solitary Callonychium brasiliense were the most frequent visitors and the principal pollinators. The frequency of visits, however, was very low (on average 1.9 visits/flower/day), resulting in a low and unbalanced legitimate pollen flow, i.e. a much lower number of pollen grains from short-styled flowers reaching stigmas of long-styles than vice versa, which in turn compromised fruit and seed set. Surprisingly, Protomeliturga catimbaui and P. turnerae, both oligolectic on flowers of the Turneraceae-clade of the Passifloraceae s.l., were very rare flower visitors and did not contribute significantly to the pollination of Turnera hermannioides. We discuss how the low visitation rate and the inefficiency of pollinators (i.e. inefficiency in promoting legitimate pollination) compromise pollen flow and, consequently, fruit and seed set in this species.     

The effectiveness of heterostyly in preventing illegitimate pollination in dish-shaped flowers

Heterostyly is thought to have evolved because it confers efficiency of cross-pollination. While it can be an alternative to an incompatibility mechanism in tube-shaped flowers, its effectiveness in dish-shaped flowers, such as those of Fagopyrum esculentum, has not been demonstrated. Stigmatic pollen loads were examined over the daily course of pollination in a planted field of this crop species. Natural pollination by bees resulted in 23% of the pollen on pin flowers and 69% on thrum flowers being legitimate. Both flower morphs therefore received the two pollen types in about the same proportions. Pin pollen constituted 74% of the pollen delivered to stigmata, even though the two morphs are present in equal numbers. Pin flowers collected about 75 pollen, and thrum flowers about 25 pollen by the end of the day of anthesis. The net result was about 15 compatible pollen per flower on both floral morphs. These results indicate that heterostyly is associated with excess pin-pollen delivery rather than excess legitimate-pollen delivery in F. esculentum.     

Ipomoea bahiensis pollinators: Bees or butterflies?

Ipomoea bahiensis presents many characters of a psychophilous nectar flower. At the investigated synanthropic site, it is, however, visited and pollinated primarily by pollen-foraging small to medium sized bees that leave the flowers well before the end of anthesis. The busy bees appear to intimidate, probably by their mere existence, butterflies that function as pollinators in early morning, but disappear from the scene after beginning of anthesis. The plant is allogamous. A higher fruit set in hand cross-pollinated flowers as compared to naturally pollinated controls indicates pollen limitation. For the first time, we observed male bees entering the closing flowers as an overnight accommodation even before noon.     

The pollination efficiency of a pollinator depends on its foraging strategy,flowering phenology,and the flower characteristics of a plant species

Honey bees and stingless bees are generalist visitors of several wild and cultivated plants. They forage with a high degree of floral fidelity and thereby help in the pollination services of those plants. We hypothesized that pollination efficiency might be influenced by flowering phenology, floral characteristics, and resource collection modes of the worker bees. In this paper, we surveyed the foraging strategies of honey bees (Apis cerana, Apis dorsata, and Apis florea) and stingless bees (Tetragonula iridipennis) concerning their pollination efficiencies. Bees showed different resource gathering strategies, including legitimate (helping in pollination as mixed foragers and specialized foragers) and illegitimate (serving as nectar robbers and pollen thieves) types of flower visitation patterns. Foraging strategies are influenced by the shape of flowers, the timing of the visitation, floral richness, and bee species. Honey bees and stingless bees mainly acted as legitimate visitors in most plants studied. Sometimes honey bees served as nectar robbers in tubular flowers and stingless bees as pollen thieves in large-sized flowers. Among the legitimate categories, mixed foragers have a comparatively lower flower visitation rate than the specialized nectar and pollen foragers. However, mixed foragers have greater abundance and higher values of the single-visit pollination efficiency index (PEi) than nectar and pollen foragers. The value of the combined parameter ‘importance in pollination (PI)’ was thus higher in mixed foragers than in nectar and pollen foragers.     

How does insect visitation trigger floral colour change?

Abstract.  1. Visitation by the key pollinator, Bombus terrestris , was implicated in inducible flower colour change in Lupinus pilosus . Behaviour at the flower and rate of visitation by these bumble bees had specific effects; exclusion of this flower visitor led to retarded onset, and reduced rate, of colour change.
2. The foraging behaviour of B. terrestris was influenced by floral colour change in L. pilosus . Choice of pre-change flowers was greater than random in relation to the proportion of colour phases available within the plant population.
3. Levels of floral manipulation that mimicked the flower handling characteristics of visiting bumble bees confirmed that triggering of the pollen release mechanism is necessary for the instigation of colour change.
4. Moreover, this study suggests that, in L. pilosus , an aspect of pollination (pollen deposition by bees and/or subsequent pollen tube growth within the style) is linked with colour change and may act as the trigger for such change.     

Genotype and rearing environment affect honeybee perception and foraging behaviour

We tested the effects of larval and preforaging rearing environment on the foraging behaviour and sucrose response thresholds of honeybees, Apis mellifera L., derived from high and low pollen-hoarding strains. Bees were reared as larvae and as preforaging adults in colonies containing high and low pollen-hoarding strains, then cofostered in unrelated common wild-type colonies from which to forage. Genotype, but not rearing environment, had strong effects on the likelihood to forage for pollen or nectar, the size of pollen or nectar load, and the concentration of sugar in the nectar they collected. Genotype and rearing environment affected adult wet weights and sucrose concentration response threshold, as measured with the proboscis extension response assay. Bees from the high pollen-hoarding strain were more sensitive to conditions of the rearing environment than were bees of the low strain. High- and low-strain bees produced different colony environments that affected developmental, behavioural and physical traits of the individuals they reared. This demonstrates how genotype and colony environment correlate and affect phenotype. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Nectar robbery by bees Xylocopa virginica and Apis mellifera contributes to the pollination of rabbiteye blueberry

Honey bees, Apis mellifera L., probe for nectar from robbery slits previously made by male carpenter bees, Xylocopa virginica (L.), at the flowers of rabbiteye blueberry, Vaccinium ashei Reade. This relationship between primary nectar robbers (carpenter bees) and secondary nectar thieves (honey bees) is poorly understood but seemingly unfavorable for V. ashei pollination. We designed two studies to measure the impact of nectar robbers on V. ashei pollination. First, counting the amount of pollen on stigmas (stigmatic pollen loading) showed that nectar robbers delivered fewer blueberry tetrads per stigma after single floral visits than did our benchmark pollinator, the southeastern blueberry bee, Habropoda laboriosa (F.), a recognized effective pollinator of blueberries. Increasing numbers of floral visits by carpenter bee and honey bee robbers yielded larger stigmatic loads. As few as three robbery visits were equivalent to one legitimate visit by a pollen-collecting H. laboriosa female. More than three robbery visits per flower slightly depressed stigmatic pollen loads. In our second study, a survey of 10 commercial blueberry farms demonstrated that corolla slitting by carpenter bees (i.e., robbery) has no appreciable affect on overall V. ashei fruit set. Our observations demonstrate male carpenter bees are benign or even potentially beneficial floral visitors of V ashei. Their robbery of blueberry flowers in the southeast may attract more honey bee pollinators to the crop.     

Pollen dynamics of bumble-bee visitation on Echium vulgare

1. We quantified pollen deposition on the stigma, pollen removal from the anthers and pollen losses in Echium vulgare , visited by workers of Bombus terrestris under controlled conditions. We used dye as a pollen analogue. Bumble-bees were trained to visit a sequence of non-emasculated flowers to estimate pollen carryover and to visit individual flowers to estimate pollen loss.
2. Carryover of pollen grains and dye particles between flowers was similar, which justifies using dye as a pollen analogue. On average 93·8% of the dye particles on the bee were carried over to the next flower. Only a small fraction of the pollen grains was deposited on the stigma (0·15%). A much larger fraction (6·1%) was lost in another way: passively during flight, through grooming or on floral parts other than the stigma. The bees removed 44% of the pollen grains from a fresh flower and 50·3% of this removed pollen adhered to the bee.
3. We predict that, using the parameters mentioned above, during a single visit to a newly opened flower, a bee collects an amount of pollen grains which will bring about 60% geitonogamous self-pollination in the next flower visited. The expected percentage of self-pollination is considerably less if bees visit flowers that have been visited before.     

Mutual reproductive dependence of distylic Cordia leucocephala (Cordiaceae) and oligolectic Ceblurgus longipalpis (Halictidae, Rophitinae) in the Caatinga

Background and Aims

The close relationship between distylic Cordia leucocephala and the bee Ceblurgus longipalpis, both endemic to the Caatinga, north-east Brazil, was investigated, emphasizing reproductive dependence, morphological adaptations of the partners, and pollen flow.

Methods

In the municipality of Pedra, in the Caatinga of Pernambuco, the breeding system and reproductive success of C. leucocephala, its interaction with flower visitors and inter- and intramorph pollen flow were determined.

Key Results

The bee Ceblurgus longipalpis, the unique flower visitor and effective pollinator of self-incompatible Cordia leucocephala, presents morphological features adapted to exploit hidden pollen and nectar in the long and narrow corolla tubes. Pollen of low-level anthers is collected with hairs on prolonged mouthparts and pollen of high-level anthers with clypeus, mandibles, and labrum, showing pollen removal from both levels with the same effectiveness. In both morphs, this results in similar legitimate, i.e. intermorph cross-pollen flow. Illegitimate pollen flow to stigmas of pin flowers, however, was much higher than to stigmas of thrum flowers. Moreover, more illegitimate pollen was transported to stigmas of pin and less to those of thrum flowers when compared with legitimate pollen flow.

Conclusions

The study reveals a one-to-one reproductive inter-dependence between both partners. Data indicate that this relationship between bee species and plant species is one of the rare cases of monolecty among bees. Monotypic Ceblurgus longipalpis, the only rophitine species of Brazil, evolved prolonged mouthparts rare among short-tongued bees that enable them to access pollen from flowers with short-level anthers hidden for bees of other species, and nectar at the base of the flower tube.     

Association between floral traits and rewards in Erysimum mediohispanicum (Brassicaceae)

Background and Aims

Floral rewards may be associated with certain morphological floral traits and thus act as underlying factors promoting selection on these traits. This study investigates whether some traits that are under pollinator-mediated selection (flower number, stalk height, corolla diameter, corolla tube length and corolla tube width) in the Mediterranean herb E. mediohispanicum (Brassicaceae) are associated with rewards (pollen and nectar).

Methods

During 2005 the phenotypic traits and the visitation rate of the main pollinator functional groups were quantified in 720 plants belonging to eight populations in south-east Spain, and during 2006 the same phenotypic traits and the reward production were quantified in 400 additional plants from the same populations.

Key Results

A significant correlation was found between nectar production rate and corolla tube length, and between pollen production and corolla diameter. Visitation rates of large bees and butterflies were significantly higher in plants exhibiting larger flowers with longer corolla tubes.

Conclusions

The association between reward production and floral traits may be a factor underlying the pattern of visitation rate displayed by some pollinators.Key words: Erysimum, floral traits, nectar, pollen, pollinator visitation rate, reward     

Effects of pollen dilution on infection of Nosema ceranae in honey bees

Multiple stressors are currently threatening honey bee health, including pests and pathogens. Among honey bee pathogens, Nosema ceranae is a microsporidian found parasitizing the western honey bee (Apis mellifera) relatively recently. Honey bee colonies are fed pollen or protein substitute during pollen dearth to boost colony growth and immunity against pests and pathogens. Here we hypothesize that N. ceranae intensity and prevalence will be low in bees receiving high pollen diets, and that honey bees on high pollen diets will have higher survival and/or increased longevity. To test this hypothesis we examined the effects of different quantities of pollen on (a) the intensity and prevalence of N. ceranae and (b) longevity and nutritional physiology of bees inoculated with N. ceranae. Significantly higher spore intensities were observed in treatments that received higher pollen quantities (1:0 and 1:1 pollen:cellulose) when compared to treatments that received relatively lower pollen quantities. There were no significant differences in N. ceranae prevalence among different pollen diet treatments. Interestingly, the bees in higher pollen quantity treatments also had significantly higher survival despite higher intensities of N. ceranae. Significantly higher hypopharyngeal gland protein was observed in the control (no Nosema infection, and receiving a diet of 1:0 pollen:cellulose), followed by 1:0 pollen:cellulose treatment that was inoculated with N. ceranae. Here we demonstrate that diet with higher pollen quantity increases N. ceranae intensity, but also enhances the survival or longevity of honey bees. The information from this study could potentially help beekeepers formulate appropriate protein feeding regimens for their colonies to mitigate N. ceranae problems.     

Bee visitation rates to cultivated sunflowers increase with the amount and accessibility of nectar sugars

Pollinators make foraging decisions based on numerous floral traits, including nectar and pollen rewards, and associated visual and olfactory cues. For insect‐pollinated crops, identifying and breeding for attractive floral traits may increase yields. In this study, we examined floral trait variation within cultivated sunflowers and its effects on bee foraging behaviours. Over 2 years, we planted different sunflower inbred lines, including male‐fertile and male‐sterile lines, and measured nectar volume, nectar sugar concentration and composition, and corolla length. During bloom, we recorded visits by both managed honey bees and wild bees. We then examined consistency in relative nectar production by comparing field results to those from a greenhouse experiment. Sunflower inbred lines varied significantly in all floral traits, including the amount and composition of nectar sugars, and in corolla length. Both wild bee and honey bee visits significantly increased with nectar sugar amount and decreased with corolla length, but appeared unaffected by nectar sugar composition. While wild bees made more visits to sunflowers providing pollen (male‐fertile), honey bees preferred plants without pollen (male‐sterile). Differences in nectar quantity among greenhouse‐grown sunflower lines were similar to those measured in the field, and bumble bees preferentially visited lines with more nectar in greenhouse observations. Our results show that sunflowers with greater quantities of nectar sugar and shorter corollas receive greater pollination services from both managed and wild bees. Selecting for these traits could thus increase sunflower crop yields and provide greater floral resources for bees.