Fly Pollination Research Articles

Ceropegia sandersonii Mimics Attacked Honeybees to Attract Kleptoparasitic Flies for Pollination

Four to six percent of plants, distributed over different angiosperm families, entice pollinators by deception [1]. In these systems, chemical mimicry is often used as an efficient way to exploit the olfactory preferences of animals for the purpose of attracting them as pollinators [2,3]. Here, we report a very specific type of chemical mimicry of a food source. Ceropegia sandersonii (Apocynaceae), a deceptive South African plant with pitfall flowers, mimics attacked honeybees. We identified kleptoparasitic Desmometopa flies (Milichiidae) as the main pollinators of C.sandersonii. These flies are well known to feed on honeybees that are eaten by spiders, which we thus predictedas the model chemically mimicked by the plant. Indeed, we found that the floral scent of C.sandersonii is comparable to volatiles released from honeybees when under simulated attack. Moreover, many of these shared compounds elicited physiological responses in antennae of pollinating Desmometopa flies. A mixture of four compounds-geraniol, 2-heptanone, 2-nonanol, and (E)-2-octen-1-yl acetate-was highly attractive to the flies. We conclude that C.sandersonii isspecialized on kleptoparasitic fly pollinators bydeploying volatiles linked to the flies' food source, i.e., attacked and/or freshly killed honeybees. The blend of compounds emitted by C.sandersonii is unusual among flowering plants and lures kleptoparasitic flies into the trap flowers. This study describes a new example of how a plantcan achieve pollination through chemical mimicry of the food sources of adult carnivorous animals.

Floral colours in a world without birds and bees: the plants of Macquarie Island.

We studied biotically pollinated angiosperms on Macquarie Island, a remote site in the Southern Ocean with a predominately or exclusively dipteran pollinator fauna, in an effort to understand how flower colour affects community assembly. We compared a distinctive group of cream-green Macquarie Island flowers to the flora of likely source pools of immigrants and to a continental flora from a high latitude in the northern hemisphere. We used both dipteran and hymenopteran colour models and phylogenetically informed analyses to explore the chromatic component of community assembly. The species with cream-green flowers are very restricted in colour space models of both fly vision and bee vision and represent a distinct group that plays a very minor role in other communities. It is unlikely that such a community could form through random immigration from continental source pools. Our findings suggest that fly pollination has imposed a strong ecological filter on Macquarie Island, favouring floral colours that are rare in continental floras. This is one of the strongest demonstrations that plant-pollinator interactions play an important role in plant community assembly. Future work exploring colour choices by dipteran flower visitors would be valuable.

Out of Africa: evidence of the obligate mutualism between long corolla tubed plant and long-tongued fly in the Himalayas.

Summary Mutualism between long corolla tubed plants and their potential pollinators, long‐tongued flies, is a classic example of coevolution, but to date, has only been reported from the regions of southern Africa. Many plant species from the Himalayas also show botanical characteristics that could be consistent with pollination by long‐tongued flies. Here, we seek the evidence of the “long‐tongued‐long tubed fly/flower” mutualism out of Africa, in a different continent and climatic region, the Himalayas.Floral traits of Himalayan region endemic alpine genus, Roscoea, indicate possible mutualism with long‐tongued flies for pollination success; however, effective pollinators of this genus are yet unknown. This study investigates whether long‐tongued flies and Roscoea purpurea in Nepal Himalayas show exclusive mutualism for their survival/reproduction.We made extensive observations of floral visitors of R. purpurea and food source of Philoliche longirostris across their wide ranges of populations in Nepal Himalayas for three consecutive years (2012–2014). To confirm the obligate reliance of R. purpurea upon P. longirostris for pollination success, manipulated pollination experiments were conducted at two populations for 2 years. Similarly foraging behavior, visitation frequency, and pollination efficiency of P. longirostris were assessed at two populations for 2 years, and its contribution for the reproductive success of R. purpurea was evaluated. Our results indicate that R. purpurea is self‐compatible but lacks autonomous selfing and obligatorily relies on P. longirostris for reproductive success. Across all populations, P. longirostris was observed as an exclusive and highly efficient pollinator of R. purpurea, while P. longirostris exclusively depends up on R. purpurea for food source.Out of Africa, this study provides the first evidence of long‐tongued fly pollination system and indicates the possibility of additional instances of such a rare phenomenon in the Himalayas. Finding of specialized pollinator of Roscoea only at its evolutionary center indicates that Roscoea species are originally pollinated by long‐tongued flies. Spatial mismatch with specialized pollinators may have induced the evolution of autonomous selfing in North Indochinese clades of Roscoea. This finding thus substantiates how geographic disjunction causes the shifting of pollination mechanism in closely related plant species.

Case study of building of conservation coalitions to conserve ecological interactions.

We engaged experts in various fields of study (pollination ecology, chemical ecology, and ethnobotany), invited community participation, and provided environmental education in an effort to conserve an endangered birthwort (Aristolochia delavayi) and a vulnerable pipevine swallowtail (Byasa daemonius). Scientists studied the uptake and sequestration of the secondary metabolites aristolochic acids from A. delavayi leaves by different stages of pipevine swallowtail as a defense mechanism; low fruit set of the myophilous A. delavayi due to pollinator limitation; and the emission of chemical signals that attract parasitic wasps by the prepupae of B. daemonius. The results of these studies were part of an education program delivered by personnel of non-governmental organizations. The program was devised to deliver information to the public about the health risks of consuming A. delavayi individuals (aristolochic-acid-associated cancers) and to establish a bridge between the public and scientific research. Following delivery of the program, the behavior of residents changed considerably. Community residents were involved in management activities, including participation in a program to promote understanding of ecological interactions between A. delavayi and B. daemonius; designing an in situ conservation site; monitoring A. delavayi and B. daemonius individuals; and promoting the natural fruit set of A. delavayi by scattering animal excrement to attract fly pollinators. The integration of scientific information and community participation appears to have resulted in an increase in abundance of threatened A. delavayi and B. daemonius populations. We believe the involvement of local people in conservation is necessary for successful species conservation.

Spatial dynamics of pollination in dioecious Shepherdia canadensis (Elaeagnaceae)

The immobility of plants and the need for third-party vectors to enact pollen transfer render pollination an inherently spatial process. Little is known about the spatial scales over which pollen transfer and plant reproductive success are dependent on mate availability in natural plant populations. Dioecious plants provide useful study systems for examining the dependence of reproductive success on spatial patterns of mate availability because potential pollen donors and recipients are unambiguous. We examined the spatial dynamics of pollination in the dioecious shrub Shepherdia canadensis (L.) Nutt. (Elaeagnaceae) at a range of spatial scales in Ivvavik National Park, Canada. On average, males occurred at higher frequencies than females across ten study sites with at least 60 S. canadensis plants per site. Although we detected substantial variation in sex ratios across sites, there was no association between sex ratio and fruit set. Instead, patterns of fruit set were significantly correlated with male density within sites, over distances of 4–6 m. The density of females and males was spatially cross correlated. Therefore, density effects appear to be driven by pollinator responses to the overall density of shrubs. A pollinator exclusion experiment indicated that syrphid flies (Family: Syrphidae) were the most important pollinators in these populations. This study demonstrates that female reproductive success in S. canadensis is limited by plant density over small spatial scales, corresponding with the short foraging distances characteristic of its fly pollinators.

Floral volatiles in a sapromyiophilous plant and their importance in attracting house fly pollinators.

Floral scent in sapromyiophilous plants often consists of complex blends with not only fetid (e.g., sulfides) but also sweet (e.g., terpenoids) volatile organic compounds, and a recent study suggests that both groups of compounds are involved in pollinator attraction. However, little is known about the number and identity of compounds involved in pollinator attraction in these deceptive plants that mimic breeding sites of fly pollinators. In the present paper, we studied flower volatiles of sapromyiophilous Periploca laevigata and their capability to elicit biological responses in one of the pollinator species, Musca domestica. Floral volatiles were collected by dynamic headspace and analyzed by gas chromatography/mass spectrometry (GC/MS), and electrophysiological (GC/EAD) and behavioral assays (two choice olfactometer) were conducted. In the floral scent of P. laevigata, we detected 44 compounds, of which indole, β-caryophyllene, and germacrene D, as well as dimethyl trisulfide, which was present in trace amounts, were electrophysiologically active in the antennae of M. domestica. However, when we evaluated in behavioral experiments the attractiveness of the electrophysiologically active compounds (complete mixture against partial mixtures or against single compounds), we found that indole was the only attractive compound for the flies.

Floral function in relation to floral structure in two Periploca species(Periplocoideae) Apocynaceae

This study comprises an investigation into the floral function in relation to the floral structure of Periploca aphylla and P. Angustifolia, using light and scanning electron microscopy. Both species display the following floral structures: style-head bearing pollen translators, shelf-like nectaries, staminal feet, nectar-collecting troughs, trisegmented corolline corona lobes and corolla lobes, and anthers and nectaries covered by unicellular hairs. Lateral segments of adjacent corona lobes are fused with half of the adaxial base of the adjacent corolla lobes, creating openings through which pollinators can reach the nectar-collecting troughs in the corolla base. Flowers are rotate with spreading corolla lobes and exposed gynostegium, thus sorting in the open-access fly pollination system. The following features are useful to distinguish the flowers of the two species: corolla color, presence or absence of long unicellular hairs and white spots size on the adaxial surface of corolla lobes, translator length, pollen tetrads color, and presence or absence of linear tetrads. It seems that the floral modifications of the two Periploca species serve to optimize pollination efficiency by attracting a wide number of pollinators, thus enhancing the pollination success of plants.

Silica particles with encapsulated DNA as trophic tracers.

Ecological networks such as food webs are extremely complex and can provide important information about the robustness and productivity of an ecosystem. In most cases, it is not feasible to observe trophic interactions between predators and prey directly and with the available methods, it is difficult to quantify the connections between them. Here, we show that submicron-sized silica particles (100-150 nm) with encapsulated DNA (SPED) enable accurate food and organism labelling and quantification of specific animal-to-animal transfer over more than one trophic level. We found that SPED were readily transferable and quantifiable from the bottom to the top of a two-level food chain of arthropods. SPED were taken up in the gut system and remained persistent in an animal over several days. When uniquely labelled SPED were applied at predefined ratios, we found that information about their relative abundance was reliably conserved after trophic level transfer and over time. SPED were also applied to investigate the flower preference of fly pollinators and proved to be a fast and accurate analysis method. SPED combine attributes of DNA barcoding and stable isotope analysis such as unique labelling, quantification via real-time PCR and exact backtracking to the tracer source. This improves and simplifies the analysis and monitoring of ecological networks.

Lethal Interactions Between Parasites and Prey Increase Niche Diversity in a Tropical Community

Ecological specialization should minimize niche overlap, yet herbivorous neotropical flies (Blepharoneura) and their lethal parasitic wasps (parasitoids) exhibit both extreme specialization and apparent niche overlap in host plants. From just two plant species at one site in Peru, we collected 3636 flowers yielding 1478 fly pupae representing 14 Blepharoneura fly species, 18 parasitoid species (14 Bellopius species), and parasitoid-host associations, all discovered through analysis of molecular data. Multiple sympatric species specialize on the same sex flowers of the same fly host-plant species-which suggests extreme niche overlap; however, niche partitioning was exposed by interactions between wasps and flies. Most Bellopius species emerged as adults from only one fly species, yet evidence from pupae (preadult emergence samples) show that most Bellopius also attacked additional fly species but never emerged as adults from those flies.

Fly pollination and duodichogamy in Bridelia stipularis and Cleistanthus sumatranus (Phyllanthaceae)

AbstractThe globally distributed family Phyllanthaceae comprises 1745 species, all of which produce unisexual flowers, and most of the species occur in the tropics. The few species in which the pollination system has been studied are pollinated by flies, wasps, or specialized moths, and at least two species are duodichogamous. Here we report on the flowering phenology and pollination of the Chinese species Bridelia stipularis and Cleistanthus sumatranus, which were studied on the tropical Hainan Island. Both species are duodichogamous and indicated to be fly‐pollinated. The calliphorid species Chrysomya megacephala, Isomyia isomyia, Pierretia sp., Hemipyrellia sp., and Achoetandrus tufifacies were the most frequent flower visitors to B. stipularis; some of these species together with syrphids (Meliscaeva cinctella, Dideopsis sp., and Eristalis sp.) were the most abundant visitors to Cl. sumatranus flowers. Fruit set in hand‐pollinated flowers was higher than in open‐pollinated flowers, but because of natural fruit abortion the difference was not significant, indicating that fly pollinators do not limit reproduction of these Phyllanthaceae species. This study provides an addition to the limited Asian literature on pollination by flies and the even more limited literature on duodichogamy. It could help to broaden our understanding for analysis of the evolution of duodichogamy in future research, but the specific ecological factors behind the evolution of this rare sexual system are still difficult to generalize.

Electrophysiological and behavioural responses of the housefly to “sweet” volatiles of the flowers of Caralluma europaea (Guss.) N.E. Br.

In sapromyiophilous plants, up to date, long range attraction of fly pollinators has been thoroughly investigated and attributed to “fetid” floral compounds, while the “sweet” floral scent fraction has not been specifically investigated and its role has received little attention. The aim of the present study was to verify if terpenoids, which are the main compounds of the floral bouquet of Caralluma europaea, play a role in the attraction of its pollinator Musca domestica. Terpinolene, α-terpinene and linalool, described as the three main volatiles of the flowers of C. europaea, were evaluated in electrophysiological investigations and blends of these compounds as well as the whole fresh flowers were used in behavioural assays. Antennae of housefly adults showed positive dose-dependent responses to all the chemicals tested. Houseflies were attracted by the odour of the fresh flowers and by the reconstructed terpenoid blend at the dose of 100 μg. At the dose of 10 μg, the blend did not produce any attraction. The results of the present study support the hypothesis that terpinolene, α-terpinene and linalool emitted by C. europaea flowers are involved in pollinator attraction and demonstrate the importance of the “sweet” scent in this sapromyiophilous species.

Geographical variations of odour and pollinators, and test for local adaptation by reciprocal transplant of twoEuropeanArumspecies

SummaryInteractions between entomophilous plants and their pollinators are one of the major factors shaping the evolution of floral features. As species are distributed in more or less connected populations, they have evolved in a geographical mosaic of co‐evolution were the outcome of the plant–pollinator interaction is likely to vary as a result of local adaptations.Arum italicumandArum maculatumare two species ofAraceae which deceive their fly pollinators by mimicking the odour of their oviposition sites. WhereasA. italicumis known to be pollinated by flies belonging to different families (i.e. opportunist),A. maculatumrelies on only two pollinating species of the familyPsychodidae throughout itsEuropean repartition area (i.e. specialist).The interannual and geographical variations of pollinators and pollinator‐attractive odours were described in several populations of the two species over two consecutive years. Furthermore, local adaptation to pollinators was tested by transplanting inflorescence‐bearing plants between two different sites and by recording the number and composition of the insect fauna trapped inside the inflorescences during anthesis as a measure of a fitness component.Pollinators and pollinator‐attractive odours of the twoArumspecies varied in time and space, but there was no clear odour structure between populations. When transplanted, inflorescences of both species trapped the same composition and number of insects as native inflorescences at a given site; this indicates that pollinator composition is highly dependent on the local availability of insects.No pattern of local adaptation was found for these two species, but local pollination conditions were shown to strongly affect the degree of geographical variations of these interactions. The lack of a clear odour geographical structure might be due to high gene flow or to similar selective pressures exerted by pollinators, and the high interindividual odour variation may be linked to the deceptive strategy adopted by the two plant species.

Are there pollination syndromes in the Australian epacrids (Ericaceae: Styphelioideae)? A novel statistical method to identify key floral traits per syndrome

Convergent floral traits hypothesized as attracting particular pollinators are known as pollination syndromes. Floral diversity suggests that the Australian epacrid flora may be adapted to pollinator type. Currently there are empirical data on the pollination systems for 87 species (approx. 15 % of Australian epacrids). This provides an opportunity to test for pollination syndromes and their important morphological traits in an iconic element of the Australian flora. Data on epacrid-pollinator relationships were obtained from published literature and field observation. A multivariate approach was used to test whether epacrid floral attributes related to pollinator profiles. Statistical classification was then used to rank floral attributes according to their predictive value. Data sets excluding mixed pollination systems were used to test the predictive power of statistical classification to identify pollination models. Floral attributes are correlated with bird, fly and bee pollination. Using floral attributes identified as correlating with pollinator type, bird pollination is classified with 86 % accuracy, red flowers being the most important predictor. Fly and bee pollination are classified with 78 and 69 % accuracy, but have a lack of individually important floral predictors. Excluding mixed pollination systems improved the accuracy of the prediction of both bee and fly pollination systems. Although most epacrids have generalized pollination systems, a correlation between bird pollination and red, long-tubed epacrids is found. Statistical classification highlights the relative importance of each floral attribute in relation to pollinator type and proves useful in classifying epacrids to bird, fly and bee pollination systems.

THE INFLUENCE OF POLLINATOR PHYLOGEOGRAPHY AND MATE PREFERENCE ON FLORAL DIVERGENCE IN A SEXUALLY DECEPTIVE DAISY

Divergent mate preferences and subsequent genetic differentiation between populations has been demonstrated, but its effects on interspecific interactions are unknown. Associated species exploiting these mate preferences, for example, may diverge to match local preferences. We explore this idea in the sexually deceptive, fly-mimicking daisy, Gorteria diffusa, by testing for association between genetic structure in the fly pollinator (a proxy for mate preference divergence) and geographic divergence in floral form. If genetic structure in flies influences interactions with G. diffusa, we expect phylogeographically distinct flies to be associated with different floral forms. Flies associated with forms exploiting only feeding behavior often belonged to several phylogeographic clades, whereas flies associated with forms exploiting male-mating behavior always belonged to distinct clades, indicating the possibility of pollinator-mediated floral divergence through phylogeographic variation in mating preferences of male flies. We tested this hypothesis with reciprocal presentations using male flies from distinct clades associated with separate floral forms. Results show that males from all clades exhibit similar preferences, making pollinator driven divergence through geographic variation in mate preference unlikely. Males, however, showed evidence of learned resistance to deceptive traits, suggesting antagonistic interactions between plants and pollinators may drive deceptive floral trait evolution in G. diffusa.

Reconstructing the origin and elaboration of insect-trapping inflorescences in the Araceae.

Floral traps are among the most sophisticated devices that have evolved in angiosperms in the context of pollination, but the evolution of trap pollination has not yet been studied in a phylogenetic context. We aim to determine the evolutionary history of morphological traits that facilitate trap pollination and to elucidate the impact of pollinators on the evolution of inflorescence traps in the family Araceae. • Inflorescence morphology was investigated to determine the presence of trapping devices and to classify functional types of traps. We inferred phylogenetic relationships in the family using maximum likelihood and Bayesian methods. Character evolution of trapping devices, trap types, and pollinator types was then assessed with maximum parsimony and Bayesian methods. We also tested for an association of trap pollination with specific pollinator types. • Inflorescence traps have evolved independently at least 10 times within the Araceae. Trapping devices were found in 27 genera. On the basis of different combinations of trapping devices, six functional types of traps were identified. Trap pollination in Araceae is correlated with pollination by flies. • Trap pollination in the Araceae is more common than was previously thought. Preadaptations such as papillate cells or elongated sterile flowers facilitated the evolution of inflorescence traps. In some clades, imperfect traps served as a precursor for the evolution of more elaborate traps. Traps that evolved in association with fly pollination were most probably derived from mutualistic ancestors, offering a brood-site to their pollinators.

Fly pollination in Cypripedium: a case study of sympatric C. sichuanense and C. micranthum

Most Cypripedium spp. are known to be pollinated by bees. However, myiophilous traits are found in some species, especially in sections Trigonopedia and Sinopedilum. Here we chose C. micranthum and C. sichuanense, two sympatric species endemic to Sichuan, China, to test whether these orchids are fly pollinated. Artificial pollination showed that both flowers are self-compatible but need pollen vectors for successful reproduction. Field observation showed that C. micranthum was pollinated by fruit flies and C. sichuanense by dung flies, both novel pollinators of Cypripedium orchids. These sympatric Cypripedium spp. are also cross-compatible, but hybrids were not found in nature. The pollination syndromes of C. sichuanense and C. micranthum fit into the complex sapromyiophily pattern. It appears that pollinator specificity is responsible for their reproductive isolation. The discovery of fly pollination in C. sichuanense and C. micranthum, which belong to the related sections Trigonopedia and Sinopedilum, suggests a shift from bee to fly pollination in the genus Cypripedium. Unlike most Cypripedium spp., the anthers of C. micranthum release discrete pollinia with narrow stalks instead of the usual amorphous pollen smears. This ‘proto-pollinarium’ is described, probably for the first time. These pollinia are most likely an adaptation for pollination by microdiptera, so the fly can carry the contents of both chambers in the same anther. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 170, 50‐58.

Lack of floral constancy by bee fly pollinators: implications for ethological isolation in an African daisy

Although divergent floral preferences of pollinating species is a likely mechanism maintaining integrity of co-occurring floral ecotypes or incipient species, reproductive isolation of floral morphs could also result from temporary floral constancy of shared pollinators. Context-dependent floral preferences have been demonstrated for many pollinating insects, suggesting that this behavior might be widespread. However, it is not yet known whether 2 plant species or morphotypes that share a single pollinator could be reproductively isolated through assortative visitation. We investigated the foraging behavior of the bee fly, Megapalpus capensis, in experimental arrays of distinct floral morphotypes of Gorteria diffusa, a South African daisy which is pollinated almost exclusively by M. capensis. Flies exhibited no intrinsic or context-dependent (according to prevailing morph) preference for floral variants nor do they display floral constancy behavior during visitation bouts. Thus, pollinator isolation through assortative visitation is an unlikely explanation for the maintenance of floral integrity across the narrow contact zones encountered in Gorteria. Despite random visitation patterns on arrays, flies exhibited different behaviors on different floral morphotypes, suggesting intrinsic responses to morphotype-specific floral cues. Our findings suggest that results of previous studies demonstrating labile preferences and constancy in insects such as bees and butterflies cannot necessarily be extrapolated to other important groups of pollinators. In pollinators, such as Megapalpus, which use flowers as arenas for multiple behaviors, including mating, and feed during long stationary bouts, learning constraints on flower handling time, the most widely accepted explanation for floral constancy, is unlikely to drive constant foraging behavior. Key words: assortative mating, Bombyliidae, floral constancy, Gorteria diffusa, pollination, reproductive isolation, South Africa, species integrity. [Behav Ecol]

Repeatability and precision in proboscis length measurements for long proboscid flies

Methods for measuring proboscides in long-tongued fly pollinators are examined with respect to fly morphology and behavior. Most ecological studies aim to measure the functional proboscis length as a response or predictor variable. Here I suggest a proxy for this, the Maximum Functional Length (MFL), obtained by combining the lengths of the prementum and labrum. I also quantify errors in proboscis measurements due to a lack of consideration of the extensible ventral rostral membrane (VRM). Results show that naïve measurements allow for substantial unrepeatable variation (mean: 7mm; maximum 14mm).

Fly pollination of dichogamous Angelica sylvestris (Apiaceae): how (functionally) specialized can a (morphologically) generalized plant be?

Because of the flower morphology and high number of insect visitors, plants of the family Apiaceae are regarded as generalists in terms of pollination systems. Recent studies however showed some degree of, at least, ecological specialization in some members of this taxonomical group and indicated interesting patterns of insect visitor behavior: discrimination between umbel sexual phases. To test whether this is true in case of other members of the family, over two years we studied the pollination biology of a common European umbellifer, Angelica sylvestris, a species considered by some authors as a supergeneralist. Although its flowers were visited by over 70 species of insects grouped in 10 morphospecies, only a relatively narrow assemblage of muscoid and syrphid flies, rather constant in both study years, contributed to pollination. These insects did not exhibit any preferences toward plant sexual phases. Based on our results and available literature, we discuss the concept of specialization/generalization of the A. sylvestris pollination system, especially in the context of the “unspecialized” floral morphology characteristic for members of the Carrot family.

Pollen transport differs among bees and flies in a human‐modified landscape

AbstractAim Dispersal distances of insect pollinators are critical in defining their contribution to landscape‐wide pollen movement and ultimately gene flow in natural and agricultural systems. We ask whether bee and fly pollinator taxa differ in their dispersal distances and transport of viable pollen in a human‐modified system.Location Canterbury and Otago region, South Island, New Zealand.Methods We captured pollen‐carrying insects travelling outside of a model mass‐flowering agricultural crop, Brassica rapa, using insect flight intercept traps at five distances (0, 100, 200, 300 and 400 m) from the pollen source. We examined pollen loads and pollen viability to determine whether pollen transport distance and viability differ among pollinator taxa.Results A total of 5453 insects were collected of which 717 individuals from 26 insect taxa were positively identified as dispersing pollen up to 400 m from the source. These taxa consisted of four species from two bee families (Hymenoptera: Apidae and Halictidae), and eight species from four fly families (Diptera: Bibiondae, Stratiomyidae, Syrphidae and Tachinidae). Apidae generally carried higher pollen loads and more viable pollen than most fly taxa. Taxa in the fly families Stratiomyidae and Syrphidae, however, carried pollen to 400 m, which is further than both bee families.Main conclusions A diverse array of wild and managed flower visitors can transport viable pollen from a pollen source to at least 400 m. Knowledge of the differences in transport distances among generalist pollinators in human‐modified environments is crucial to understand the potential extent to which (1) pollen transport can facilitate gene flow and (2) unwanted hybridization may occur between crops and related weeds.