Flowers of alien invasive plants can be pollen limited due to a lack of effective pollinators. The alien Impatiens glandulifera is predominantly visited by bumblebees in its invaded range. There bumblebees pollinate I. glandulifera, but it remains unclear whether foraging behaviour or bumblebee or flower morphology affects effectiveness. We investigated the effectiveness of native bumblebee (Bombus pascuorum) pollinators in Ireland by quantifying pollen deposition and removal, and seed productio
n after a single bumblebee visit. Morphological characteristics of flowers and bumblebee body parts were measured to determine their influence on pollen deposition and removal. B. pascuorum is a highly effective pollinator of the alien due to its high visitation frequency, the morphological fit with flowers and individuals removing large pollen quantities and inducing maximum seed set after a single visit. The impact of native bumblebees on I. glandulifera pollination and the implications of the pollination mechanism of the alien for its successful spread are discussed.
Flower scarcity outside coffee flowering periods leads to a decline of pollinators' abundance and diversity possibly through death or migration. The objective of this study was to assess whether other flowering plants within and around coffee farms act as alternative floral resources that may impact on abundance and diversity of pollinators of coffee flowers. Bee pollinators of coffee were assessed and identified for a period of 27 months. Their abundance and diversity were examined within and a
round organically and conventionally managed coffee farms in Kiambu District in Kenya. This study provides evidence that 42 plant species from 19 families were alternative floral resources for bees that pollinate coffee. Bee pollinators of coffee were observed to visit coffee flowers as well as other flowering plants close by. Significant relationship existed between plant species and bee species richness in the organic farming (R2=0.5918; P<0.0001) and in conventional farming (R2=0.6744; P<0.0001). Therefore in coffee monocultures, presence of other flowering plants should be encouraged to support bee pollinators when coffee is not flowering and to enhance abundance and diversity of bees visiting coffee flowers.
Tropical dry deciduous forest is an endangered ecosystem whose plant-pollinator relationships are little known. We characterised a portion of the web of interactions between flowering plants and flower visitors in the Kirindy Forest of the Menabe region of west-central Madagascar. Taking a plant-centered approach, we observed individuals of the 5 most abundant native plant species that were coming into flower at the end of the annual dry season, and recorded all identifiable flower-visitors. Tak
ing a visitor-centered approach, we walked a network of established trails and listened for distinctive calls of a common flower-visiting bird, noting the plant species visited. The former approach revealed connections among the early-flowering species via birds and insects, whereas the latter confirmed these connections and added an additional plant species. Flowers of the 6 plant species were visited on average by 5.5 animal species, while 10 visitor species for which we had reasonable samples frequented on average the flowers of 3.3 plant species. These qualitative results resemble those reported from other temperate and tropical webs, in that interactions appeared to be relatively generalised by pollinator species and body plan (e.g., birds vs. bees). Also in agreement, the visitation web was significantly nested, with more-specialised species tending to interact with mutualistic partners that were themselves more generalised. In addition to documenting previously-unreported interactions, therefore, this preliminary web conforms to more widespread patterns emerging for pollination systems at the community level.
Many plant species rely on female bumble bee workers for pollen transfer. However, male bumble bees, which differ both behaviourally and morphologically from female workers, also visit many species of flowering plants and may transfer pollen differently. Males can outnumber workers on some plants, particularly those that flower late in the season. In laboratory experiments, we compared the movement patterns of male bees and female workers on an artificial flower array. We also compared the polle
n transfer efficiency of males and workers foraging on Brassica rapa flowers. Males travelled between patches of flowers more often than workers, which may be an effective method for reducing geitonogamy in plants. Males also had lower foraging rates, longer flower handling time, and transferred more pollen from one B. rapa flower to the next than workers did. These caste-based differences in pollinating behaviour suggest that, under certain circumstances and on a per-visit basis, male bumble bees may be better pollen vectors than female foragers. Furthermore, our results emphasize the need to avoid species-wide generalizations of pollinator effectiveness.
Ananas comosus var comosus (L.) Merr. is the third most important tropical fruit in the world production and the leading foreign exchange earner among fresh fruits exported from Ghana. A survey was conducted in pineapple farms in the Central region of Ghana to identify floral visitors and their activities on the flowers. Nectar concentration and energetics and effect of floral visitors on fruit production were determined. Fourteen species of butterflies and one ant species were the main insect f
loral visitors as well as four species of sunbirds. The mean nectar concentration was 23.3% (± 0.39, SE) and pollination limitation did not significantly affect fruit yield (weight: p = 0.285; length: p = 0.056; width: p= 0.268). The study showed that butterflies, ants and sunbirds are the main floral visitors on A. comosus. However their visits did not results in pollination and fruit production was not affected in any way by floral visitation. Still, it was found that A. comosus provides an important nectar resource for its foragers. Even if pollination is not crucial in pineapple cultivation, it is still essential in pineapple breeding programs to promote genetic diversity and conservation.
The co-occurrence of several dimensions of resource separation between coexisting consumers strengthens the hypothesis that the separation arose from and/or ameliorates interspecific competition. The two most common pollinators of the California endemic plant Clarkia xantiana ssp. xantiana (Onagraceae), the bees Hesperapis regularis (Mellitidae) and Lasioglossum pullilabre (Halictidae), are known to partition flower resources by flower colour. Here we asked whether H. regularis and L. pullilabre
also partition flower resources by diurnal foraging schedule and by food type (pollen versus nectar). We also quantified diurnal patterns of nectar availability, expected to be related to foraging schedules and forager responses to flower colour. The diurnal schedules of the two species differed distinctly and significantly. The majority of L. pullilabre foraging visits occurred before midday, while the majority of H. regularis visits occurred afterwards. The two species foraged for alternative food types at significantly different frequencies—nectar and pollen approximately equally frequently for H. regularis, pollen almost exclusively for L. pullilabre. Nectar standing crop declined with time of day, but it did not clearly reflect or explain previously identified colour-morph preferences. The major pollinators of C. xantiana ssp. xantiana exhibit multiple forms of ecological separation that likely reduce the intensity of competition for floral resources.
In this study we used a portable event-triggered video surveillance system for monitoring flowervisiting bumblebees. The system consist of mini digital recorder (mini-DVR) with a video motion detection (VMD) sensor which detects changes in the image captured by the camera, the intruder triggers the recording immediately. The sensitivity and the detection area are adjustable, which may prevent unwanted recordings. To our best knowledge this is the first study using VMD sensor to monitor flower-vi
siting insects. Observation of flowervisiting insects has traditionally been monitored by direct observations, which is time demanding, or by continuous video monitoring, which demands a great effort in reviewing the material. A total of 98.5 monitoring hours were conducted. For the mini-DVR with VMD, a total of 35 min were spent reviewing the recordings to locate 75 pollinators, which means ca. 0.35 sec reviewing per monitoring hr. Most pollinators in the order Hymenoptera were identified to species or group level, some were only classified to family (Apidae) or genus (Bombus). The use of the video monitoring system described in the present paper could result in a more efficient data sampling and reveal new knowledge to pollination ecology (e.g. species identification and pollinating behaviour).
Observation is a critical element of behavioural ecology and ethology. Here, we propose a similar set of techniques to enhance the study of the diversity patterns of invertebrate pollinators and associated plant species. In a body of avian research, cameras are set up on nests in blinds to examine chick and parent interactions. This avoids observer bias, minimizes interference, and provides numerous other benefits including timestamps, the capacity to record frequency and duration of activitie
s, and provides a permanent archive of activity for later analyses. Hence, we propose that small video cameras in blinds can also be used to continuously monitor pollinator activity on plants thereby capitalizing on those same benefits. This method was proofed in 2010 in the alpine in BC, Canada on target focal plant species and on open mixed assemblages of plant species. Apple ipod nanos successfully recorded activity for an entire day at a time totalling 450 hours and provided sufficient resolution and field of view to both identify pollinators to recognizable taxonomic units and monitor movement and visitation rates at a scale of view of approximately 50 cm2. This method is not a replacement for pan traps or sweep nets but an opportunity to enhance these datasets with more detailed, finer-resolution data. Importantly, the test of this specific method also indicates that far more hours of observation - using any method - are likely required than most current ecological studies published to accurately estimate pollinator diversity.
We compared flower-visitors of the endangered plant Eriogonum pelinophilum, at relatively undisturbed and highly disturbed sites. We found no difference between sites in flower visitation rate or species richness of flower-visitors; species diversity of flower-visitors was higher at disturbed than at undisturbed sites but there was no difference in equitability. We found significant differences in total E. pelinophilum pollen carried on the body among 14 abundant bee species; eight abundant wasp
species; and 12 abundant fly species. Both bee and wasp species carried significantly more pollen on the ventral compared to dorsal segments of the body; pollen on the body of fly species was more equally distributed across body surfaces. Total pollen carried on flower-visitor bodies was significantly related to visitor length, suggesting that larger visitors were more effective pollinators. Total Pollination Value, a measure combining both visitor abundance and body pollen was greater at the disturbed site than the undisturbed site, further suggesting that pollination in fragments of this rare species is not a major concern. We conclude that the high diversity of insect flower-visitors and the generalized nature of E. pelinophilum flowers make a special management programme to conserve pollinators unnecessary. Conservation of this buckwheat is best achieved by simple habitat preservation, together with a program to enlist private citizens to include buckwheat plants in their backyard gardens.
In this paper, we develop a method, termed the Interaction Distribution (ID) method, for analysis of quantitative ecological network data. In many cases, quantitative network data sets are under-sampled, i.e. many interactions are poorly sampled or remain unobserved. Hence, the output of statistical analyses may fail to differentiate between patterns that are statistical artefacts and those which are real characteristics of ecological networks. The ID method can support assessment and inference
of under-sampled ecological network data. In the current paper, we illustrate and discuss the ID method based on the properties of plant-animal pollination data sets of flower visitation frequencies. However, the ID method may be applied to other types of ecological networks. The method can supplement existing network analyses based on two definitions of the underlying probabilities for each combination of pollinator and plant species: (1), pi,j: the probability for a visit made by the i’th pollinator species to take place on the j’th plant species; (2), qi,j: the probability for a visit received by the j’th plant species to be made by the i’th pollinator. The method applies the Dirichlet distribution to estimate these two probabilities, based on a given empirical data set. The estimated mean values for pi,j and qi,j reflect the relative differences between recorded numbers of visits for different pollinator and plant species, and the estimated uncertainty of pi,j and qi,j decreases with higher numbers of recorded visits.
The impact of introduced species on native organisms is one of the main conservation concerns around the world. To fully understand the effect of introduced pollinators on native plants, it is important to know the reproductive biology of the focal species, especially its pollination biology. In this study we examined the breeding system of the endangered tree Goetzea elegans (Solanaceae), and compared pollination effectiveness of the two main floral visitors, Coereba flaveola (an avian nectariv
ore), and Apis mellifera (the introduced European Honeybee). We assessed the breeding system of G. elegans by applying several pollination treatments to flowers of cultivated trees to test fruit set, seed set, and seed viability. We also examined the pollination efficiency of A. mellifera and C. flaveola , and compared all the treatments with positive and negative controls. Our results indicate that the introduced honeybee A. mellifera is as efficient as the native bird C. flaveola in pollinating the flowers of G. elegans. This study also showed that G. elegans requires crossâ€“pollination for fruit and seed set, and to obtain high seed viability rates. Despite the fact that many studies report exotic species as detrimental for native organisms, we document a case where an introduced insect has a beneficial impact on the reproductive biology of an endangered tropical tree.
Typological schemes that describe putative floral adaptations for pollinators have played a central role in pollination biology. In 1882 the prominent German botanist and Darwinist Hermann Müller commented critically on a precursor of modern versions of such “pollination syndromes” that had been developed by his Italian colleague Federico Delpino. Delpino also was a self-proclaimed Darwinist, but in fact adhered to teleology— explanation beyond nature. As a consequence he viewed his typology as
reflecting a deeper ideal and thus as rigidly true, and rejected as unimportant any visitors to flowers that it did not predict. Although Müller also classified flowers as to pollinators, he considered such schemes to be fallible, and pondered what diversity and variation in floral visitors might mean. Müller’s comments, which we translate here, are of interest given that appeals to teleology have resurfaced from time to time in discussions of pollination syndromes, and more importantly because his warning against taking typological schemes too literally remains valid. Typology is a useful tool in biology, including pollination biology, but care must be taken that it does not replace nature as perceived reality.
Floral syndromes are traditionally thought to be associated with particular pollinator groups. Ornithophilous flowers tend to have traits that facilitate bird pollination such as having long, narrow, tubular corollas, often vivid coloration and diluted, sucrose-rich nectar. However, recent studies have shown that flowers attract a broader spectrum of visitors than might be expected. Furthermore, the classification of floral visitors as ‘robbers’ or ‘pollinators’ often is not as simple as it seem
s, as pollinators can at times act as robbers and vice versa. We studied the species composition, behaviour and ecology of floral visitors, including potential pollinators and robbers, of Heliconia angusta (Heliconiaceae), an endemic understory herb of the Atlantic Rainforest of Brazil. In addition, the impact of the plant inflorescence attractiveness and of weather and light conditions on visitor abundance and frequency was investigated.
Flower visitors were found to be scarce with a total of only 151 visits being observed during 120 h of field observations. A stingless bee species (Trigona sp.) appeared to be the most abundant visitor to the ornithophilous flowers of H. angusta, along with four different species of hummingbirds and two species of butterflies. We consider Trigona sp. rather as pollen robber, but which still has the potential to be a secondary pollinator, whereas the hummingbirds were the principle legitimate visitors. Most flower visitors were recorded between 9.00 am and 1.00 pm with a higher number visiting under semi-shaded conditions than in full shade. Hummingbird numbers increased with flower abundance while the other visitor group numbers were not affected.
Cantharophily is reported for the first time in a Brazilian asclepiad, involving the mylerid Astylus variegatus and the nectariferous flowers of Oxypetalum banksii, a plant mainly pollinated by wasps. The use of nectar as food by A. variegatus, considered pollinivorous and granivorous, is also novel. The mutual interaction described here is an example of a plant-pollinator interaction with generalist insects visiting a plant with a specialized pollination system. It's also temporary and occasion
al and, therefore, is often overlooked in studies of plant-pollinator interactions. In this study, we found that the casual meeting between O. banksii and A. variegatus was a key event for the reproduction of both.
Pollinator exclusion bags for small herbaceous plants are much more convenient to apply and remove if their bottom edge is made in the form of a cloth tunnel loaded with sand to conform to the terrain. Damage and inadvertent selfing of flowers are minimized.
The floral biology and flower visitors of the tropical palms Johannesteijsmannia altifrons, J. magnifica and J. perakensis were investigated. We combined the data from this study with published data of J. lanceolata to give an overview of the reproductive biology and pollination system of the genus. Anthesis peaks from 0500–1100 hrs when the inflorescences are visited mainly by flies, beetles and stingless bees (Trigona), the last are potential pollinators. The breeding system is facultative sel
fing, indicating the ability of the species to reproduce in the absence of pollinators or in isolation.
To inspire new ideas in research on pollination ecology, we list the most important unanswered questions in the field. This list was drawn up by contacting 170 scientists from different areas of pollination ecology and asking them to contribute their opinion on the greatest knowledge gaps that need to be addressed. Almost 40% of them took part in our email poll and we received more than 650 questions and comments, which we classified into different categories representing various aspects of poll
ination research. The original questions were merged and synthesised, and a final vote and ranking led to the resultant list. The categories cover plant sexual reproduction, pollen and stigma biology, abiotic pollination, evolution of animal-mediated pollination, interactions of pollinators and floral antagonists, pollinator behaviour, taxonomy, plant-pollinator assemblages, geographical trends in diversity, drivers of pollinator loss, ecosystem services, management of pollination, and conservation issues such as the implementation of pollinator conservation. We focused on questions that were of a broad scope rather than case-specific; thus, addressing some questions may not be feasible within single research projects but constitute a general guide for future directions. With this compilation we hope to raise awareness of pollination-related topics not only among researchers but also among non-specialists including policy makers, funding agencies and the public at large.
Pollination Ecology is a dynamic field of scientific research constantly adopting novel methods and making progress in understanding the interactions between plants and their pollinators. A recent paper listed the main scientific questions in this field focussing on the ecological and biological system itself. Here, we follow up on that paper and present some ideas on how to broaden our perspective and explore the role that pollination research can play in answering both ecological and societal
questions relevant to a range of different stakeholders. We hope this paper may be useful to researchers aiming at improving both the scientific and societal impact of their research.
Urban landscapes include a mix of biotic and anthropogenic elements that can interact with and influence species occurrence and behaviour. In order to outline the drivers of bee (Hymenoptera: Apoidea) occurrence in tropical urban landscapes, foraging patterns and community characteristics were examined at a common and broadly attractive food resource, Tecoma stans (Bignoniaceae). Bee visitation was monitored at 120 individual resources in three cities from June 2007 to March 2009. Resource chara
cteristics, spatial distribution, and other local and regional landscape variables were assessed and then used to develop descriptive regression models of forager visitation. The results indicated that increased bee abundance and taxon richness consistently correlated with increased floral abundance. Resource distribution was also influential, with more spatially aggregated resources receiving more foragers. Individual bee guilds had differential responses to the variables tested, but the significant impact of increased floral abundance was generally conserved. Smaller bodied bee species responded to floral abundance, resource structure, and proximity to natural habitats, suggesting that size-related dispersal abilities structure occurrence patterns in this guild. Larger bees favoured spatially aggregated resources in addition to increased floral abundance, suggesting an optimization of foraging energetics. The impact of the urban matrix was minimal and was only seen in generalist feeders (African honey bees). The strongly resource-driven foraging dynamics described in this study can be used to inform conservation and management practices in urban landscapes.
The presence of bees is typically accompanied by the humming sound of their flight. Bees of several tribes are also capable of pollen collecting by vibration, known as buzzing behaviour, which produces a buzzing sound, different from the flight sound. An open question is whether bee species have species-specific buzzing patterns or frequencies dependent of the bees' morphology or are capable to adjust their indivudual buzzing sound to optimize pollen return. The investigations to approach this i
ssue were performed in northeastern Brazil near Recife in the state of Pernambuco. We present a new field method using a commercially available portable system able to record the sound of bees during flight and buzzing at flowers. Further, we describe computer linguistical algorithms to analyse the frequency of the recorded sound sequences. With this method, we recorded the flight and buzzing sequences of 59 individual bees out of 12 species visiting the flowers of Solanum stramoniifolium and S. paniculatum. Our findings demonstrate a typical frequency range for the sounds produced by the bees of a species. Our statistical analysis shows a strong correlation of bee size and flight frequency and demonstrate that bee species use different frequency patterns.
In animal-pollinated plants, reproductive success is commonly limited by pollen availability, which can occur in environments where pollinator activity is scarce or variable. Extended floral longevity to maximize a plant’s access to pollinators may be an adaptation to such uncertain pollination environments. Here, we investigated the effects of flower exposure time to pollinators on female fertility (fruit and seed set) in the bee-pollinated woodland herb Trillium grandiflorum, a species with lo
ng-lived flowers (~17-21 d) that blooms in early spring when pollinator activity is often variable. We experimentally exposed flowers to pollinators for different amounts of time to determine the extent to which floral longevity influenced reproductive success. The amount of time that flowers were exposed to pollinators significantly increased fruit set and seed set per flower, but not seed set per fruit. Our results provide experimental evidence that long floral life spans may function as a ‘sit-and-wait’ pollination strategy to increase the amount of exposure time to pollinators and promote seed set in the unpredictable pollination environments often experienced by early spring ephemerals. In large populations with infrequent pollinator visitation, as commonly occurs in T. grandiflorum, pollination may be a largely stochastic process.
The reproductive biology of 13 monoecious species of Begonia L. (Begoniaceae) that occur in the Serra do Mar State Park, São Paulo, Brazil, was investigated. These species flower annually and present flowers with mostly white tepals, light and sweet odour, pollen as a reward but no nectar, numerous yellow stamens, and coiled yellow styles. Anthesis is diurnal and floral duration is long (6 - 15 days). The unusual appearance of pistillate flowers of these species supports the view that they are i
ntersexual mimics of the staminate flowers. Despite consistently high levels of fruit-set, none of the 11 species tested proved to be apomictic. In contrast to earlier reports of self-compatibility in Begonia, self-pollinations of B. integerrima and B. itatinensis produced no fruits or seeds, and the complete absence of pollen tubes in the styles of self-pollinated flowers of B. integerrima suggests that the species is genetically self-incompatible. Flowers pollinated under natural conditions showed many pollen tubes that reached ovules, suggesting that adequate numbers of compatible pollen grains had been transported by pollinators. The principal pollinators were small bees of the Apidae and Halictidae. Ten species of bees were observed to visit eight species of Begonia, and pollen collection occurred by means of vibration, except for Trigona spinipes. Visits to rewarding staminate flowers were significantly more frequent than visits to unrewarding pistillate flowers. Duration of visits to pistillate flowers also was significantly shorter than the duration of visits to staminate flowers. We conclude that visits to pistillate flowers occur by mistake but with sufficient frequency to allow for successful reproduction in natural populations of these species.
Cocoa is strictly entomophilous but studies on the influence of the ecosystem on insect pollinators in cocoa production systems are limited. The abundance of cocoa pollinators and pod-set of cocoa as influenced by a gradient of farm distances from natural forest and proportion of plantain/banana clusters in or adjacent to cocoa farms were therefore investigated. Cocoa pollinators trapped were predominantly ceratopogonid midges hence, analyses were based on their population. Variation in farm dis
tance to forest did neither influence ceratopogonid midge abundance nor cocoa pod-set. However, we found a positive relationship between pollinator abundance and pod set and the proportion of plantain/banana intercropped with cocoa. The results suggest appropriate cocoa intercrop can enhance cocoa pollination, and the current farming system in Ghana can conveniently accommodate such interventions without significant changes in farm practices.
As a result of different levels of pollination efficiency of pollinators, knowledge on appropriate pollinators of a plant has become important, especially in the management and conservation of both the pollinators and the plants. In this study, the pollination efficiency of Apis mellifera and Xylocopa olivacea, important pollinators of Luffa aegyptiaca, were assessed in the southern coastal part of Ghana from June 2009 to September 2010. Pollination efficiency of A. mellifera and X. olivacea was
estimated in terms of fruit set and fruit size. Further, data on daily and seasonal nectar dynamics of Luffa aegyptiaca were collected. In the early mornings (0600-0700), X. olivacea was the most frequent visitor (0.47 min-1) on the female flowers compared to A. mellifera (0.13 min-1). The mean nectar (sugar) concentration in the dry season was 36.58 ± 0.55 %, which was higher than the 34.03 ± 0.38 % obtained for the rainy season (F = 14.986; df = 2; P < 0.0001). Total amount of sugar in the early mornings was 1.88 ± 0.37 mg which was higher than 0.28 ± 0.04 mg in the mid mornings (χ2 = 14.33, df = 1, P < 0.0001). Fruits that developed from flowers that had received a single visit from X. olivacea had a mean weight of 428.7g and were 1.5 times heavier than fruits from flowers visited by A. mellifera (286.76 g). X. olivacea was more efficient than A. mellifera in terms of number of fruit set per single visit. This study has provided some knowledge on pollination ecology of L. aegyptiaca, which can be exploited to improve fruit production in commercially grown vine crops.
This study was conducted in an effort to understand the effects of spatial variations in pollinator assemblage due to habitat isolation on the reproductive performance of perennial plant species. Variations in pollinator assemblage structure (abundance, diversity and Shannon-Wiener index) were studied at three widely isolated (100 to 200 km apart) nature reserves of Southern Punjab, Pakistan, in order to explore its effects on reproductive performance of Prosopis juliflora. Species richness and
abundance were highest in Pirowal Sanctuary followed by Chichawatni Sanctuary and Chak Katora forest reserve. The pollination system of P. juliflora was highly generalized with 77 insect visitor species in four orders among all the three sites. However, pollinator assemblage varied significantly in composition among the sites. Out of the four reproductive parameters considered, the number of pods per raceme and germination varied significantly among the three locations. The reproductive performance of P. juliflora in terms of number of pods per raceme and germination improved with abundance of pollinators.
Early successional landscapes created through right-of-way management are increasingly being viewed as potential pollinator conservation zones. Habitat development initiatives in these landscapes are active, but vetted support for particular techniques and strategies is limited and technical information is diffuse. Our review examined 34 published works in order to outline the current depth and breadth of investigation into the conservation and management of pollinators on rights-of-way along ro
adsides and underneath electrical transmission corridors. Taxonomic surveys dominate the literature and are focused on diversity patterns in butterflies and moths; the importance of host plant presence as a determinant of abundance and diversity patterns is highlighted in select cases. Keystone agricultural pollinators, including managed and wild bees, have only been examined in a handful of studies. Investigations of pollinator service provisioning within or adjacent to rights-of-way are also lacking. There are no studies of vertebrate or migratory pollinating species. Contrasting results are reported for the impact of disturbance regimes associated with management (mowing and herbicide use), and there is only limited consideration of any potential negative impacts. Studies were also focused on Europe and North America, omitting rapidly developing regions that are experiencing the highest rates of landscape conversion, and where dependence on wild pollinators for food production is high. Successful pollinator species management requires more refined information, and significant gaps exist in the understanding of how rights-of-way can benefit all pollinators, we therefore encourage further management-based investigations in order to develop best practices.
Interactions with pollinators are thought to play a significant role in determining whether plant species become invasive, and ecologically generalised species are predicted to be more likely to invade than more specialised species. Using published and unpublished data we assessed the floral biology and pollination ecology of the South American native Nicotiana glauca (Solanaceae) which has become a significant invasive of semi-arid parts of the world. In regions where specialised bird pollinato
rs are available, for example hummingbirds in California and sunbirds in South Africa and Israel, N. glauca interacts with these local pollinators and sets seed by both out-crossing and selfing. In areas where there are no such birds, such as the Canary Islands and Greece, abundant viable seed is set by selfing, facilitated by the shorter stigma-anther distance compared to plants in native populations. Surprisingly, in these areas without pollinating birds, the considerable nectar resources are only rarely exploited by other flower visitors such as bees or butterflies, either legitimately or by nectar robbing. We conclude that Nicotiana glauca is a successful invasive species outside of its native range, despite its functionally specialised hummingbird pollination system, because it has evolved to become more frequently self pollinating in areas where it is introduced. Its invasion success is not predictable from what is known of its interactions with pollinators in its home range.
The Mexican native bumblebee Bombus ephippiatus Say was evaluated as a potential pollinator of greenhouse tomatoes (Solanum lycopersicon L.). The experiments were performed at San Andrés Cholula, Puebla, Mexico, from June to December 2004 in two 1 000 m2 greenhouses planted with tomatoes of the cultivar Mallory (Hazera ®). For the experiments, we used two colonies of Bombus ephippiatus, reared in the laboratory from queens captured in the field. Four treatments were applied to 20 st
udy plants: pollination by bumble bees, manual pollination, pollination by mechanical vibration and no pollination (bagged flowers, no vibration). We measured percentage of flowers visited by bumble bees, number of seeds per fruit, maturing time, sugar content, fruit weight and fruit shape. All available flowers were visited by bumblebees, as measured by the degree of anther cone bruising. The number of seeds per fruit was higher for bumble bee-pollinated plants as compared with plants pollinated mechanically or not pollinated and was not significantly different between hand-pollinated and bumble bee-pollinated plants. Maturation time was significantly longer and sugar content, fresh weight and seed count were significantly higher for bumblebee pollinated flowers than for flowers pollinated manually or with no supplemental pollination, but did not differ with flowers pollinated mechanically.
There is a severe information gap regarding wild bees in northern Mexico. The present study is a contribution to knowledge of the distribution, habitat preferences and floral usage patterns of bees of the genus Xylocopa in the state of Nuevo León. Field sampling was done using aerial net and pan traps (yellow, blue, white and pink) at 35 sites throughout the state. Xylocopa species were found at only seven of these sites. Four of the five species, previously reported for the state were collected
plus two new state records (Xylocopa micans and X. strandi), bringing the total number of species in the state to seven. Individuals were collected visiting only flowers of the Fabaceae and Bignoniaceae families, and they occurred primarily in shrub lands and disturbed areas.
Although avocado is native to Mexico, there are no comparative measures in this country on the performance of its flower visitors as pollinators. The contribution of honey bees, flies and wasps to the pollination of avocado from tropical Mexico was assessed by comparing abundance, speed of flower visitation, quantity of pollen carried per individual and pollen deposited on virgin flowers after single visits. The values of abundance and frequency of flower visitation with pollen deposition were c
ombined to obtain a measure of pollinator performance (PP). The most abundant insects on avocado were flies (mean ± SE: 15. 2 ± 6.2), followed by honey bees (9.4 ± 6.3) and wasps (4.2 ± 3.1) (ANOVA F = 91.71, d.f. = 2,78; P < 0.001). Honey bees and wasps visited similar number of flowers (8.2 ± 3.1 and 7.5 ± 2.6 respectively), and more than flies (4.1 ± 1.2) in the same time period (F = 17.63; d.f. = 2,33; P < 0.01). Although flies carried far more avocado pollen on their bodies (44.9 ± 16.8 grains) compared with honey bees and wasps, (21.3 ± 6.2 and 23.8 ± 8.11 grains, respectively; H = 26.522, df = 2, P = 0.001), the number of pollen grains deposited on a stigma after a single visit was similar for the three taxa (2-5). There was evidence for a significant and similarly positive PP of both honey bees and flies as avocado pollinators over wasps, given their abundance, potential for pollen transport and deposition of pollen on stigmas.
In invasion ecology, potential impacts of aliens on native flora are still under debate. Our aim was to determine the pollinator mediated effects of both proximity and abundance of an alien species on the reproductive success of natives. We chose the highly invasive Impatiens glandulifera and two native species: Epilobium angustifolium and Aconitum napellus ssp. lusitanicum . These species share characteristics allowing for pollination interactions: similar biotopes, overlapping flowering period
s and same main pollinators. The effects of abundance (5, 25 and 100 individuals) and proximity (0 and 15 m) of the alien on visitation rate, insect behaviour, pollen deposition and reproductive success of both natives were investigated during 2 flowering seasons. We used centred visitation rates as they can be directly interpreted as a positive or negative effect of the invasive. Both abundance and proximity of the alien increased bumblebee visitation rates to both natives. On the other hand, abundance of the exotic species had a slight negative effect on honeybee visits to natives while its proximity had no effect. The behaviour of bumblebees changed as visitors left significantly more often the native plants for I. glandulifera when its abundance increased. As a consequence of this “inconstancy”, bees deposited considerable quantities of alien pollen on native stigmas. Nevertheless, this interspecific pollen transfer did not decrease seed set in natives. Self-compatibility and high attractiveness of both native species probably alleviate the risk of altered pollinator services and reproductive success due to the invader in natural populations.
Attracting pollinators and achieving successful reproduction is essential to flowering plant species, which evolved different strategies to cope with unpredictable pollination service. The ability of selfing is most widespread and represents a reproductive insurance under varying conditions. In this study, we investigated reproductive success in Centaurea cyanus, a self-incompatible declining Asteraceae species. We measured seed set under outcrossing and autonomous selfing and assessed the impac
t of capitulum structure (i.e., the number of disc florets) on reproductive success. We report that the incompatibility system is either flexible or evolving a breakdown in this species, since autonomous selfing often resulted in production of few seeds. We also show that capitulum structure has a strong impact on reproduction, with smaller inflorescences presenting a better ability to self than larger ones, while larger inflorescences performed better than smaller ones when cross-pollinated. Variable capitulum structure in this Asteraceae species may therefore represent a reproductive strategy to achieve efficient reproduction under diverse pollination environments. Our results also suggest that this declining species might be disrupting its auto-incompatibility system in response to reduced habitats and declining population sizes.
Pollinators feed on the pollen, nectar, and other plant exudates that are associated with flowers. As a result of this feeding activity, pollen becomes attached to them. Analysis of this pollen can reveal what they eat, their dispersal patterns in and around cropping systems, and their role in pollination. However, finding pollen on and or in a pollinator depends on the technique used to recover pollen. Two very easy techniques are described in detail that have been used to recover pollen from a
variety of pollinators including beneficial and harmful insects, spiders, bats, and other pollinators. These techniques can be used to recover pollen from internal tissues (gut, alimentary canal, crop, etc.), external tissues (proboscis, legs, eyes, etc.), or both. By using the proper technique, better pollen recovery can be made and thus better data can be obtained about the pollinators, the foods they eat, the plants they pollinate, their migration routes and source zones.
Specialization in plant-pollinator systems represents an important issue for both the ecological understanding and conservation of these systems. We investigated the extent to which the bumblebee Bombus hortorum (Linnaeus) is the main potential pollinator of Common Foxglove, Digitalis purpurea L. Twenty D. purpurea patches were selected in North Yorkshire, U.K., ten each in woodland and garden or park habitat. All insects visiting D. purpurea within the patches were recorded over seventy 30-min
bouts. The relative frequency of insect visitors to other flowering plant species within 15 m of each patch was also determined. B. hortorum and B. pascuorum were the two most frequent visitors to D. purpurea, accounting for 82 - 92% and 3 -17%, respectively, of all insect visits (n = 1682), depending on habitat. B. hortorum showed a significant preference for visiting D. purpurea relative to its frequency of visits to other available plant species. The relationship of D. purpurea with B. hortorum, which pollinates several plant species with long corollas, therefore represents a potential case of asymmetric specialization, albeit one that may vary spatially. Because D. purpurea reproduction appears dependent on insect pollination, B. hortorum and B. pascuorum may help underpin the viability of D. purpurea populations.
Pollinator preferences for phenotypic characters, including floral orientation, can affect plant reproductive success. For example, hawkmoths and syrphid flies prefer upward- over downward-facing flowers in field experiments. Although such preferences suggest a cost of pendent flowers in terms of pollinator attraction, we cannot rule out the possibility that the preferences have been affected by prior experience: pollinators might choose the same type of flowers to which they have already become
accustomed. To test for innate preference, we observed bumble bees foraging on an array of upward- and downward-facing artificial flowers. Without any prior experience with vertical flowers, 91.7% bees chose an upward-facing flower at the very first visit. In addition to this innate preference, we also found that the preference was strengthened by experience, which suggests that the bees learned upward-facing flowers were easier to handle. Although bumble bees may concentrate on pendent flowers in the field, such learned preferences are evidently imposed on a template of upward-facing preference. Because bee-pollinated pendent flowers face particular difficulties in attracting visits, therefore, we expect them to compensate through other means, such as greater floral rewards.
Floral visitor species are often assumed to act either mutualistically towards plants (as pollinators) or to exploit them (as nectar-robbers or as nectar or pollen thieves). We investigated the reproductive biology of pointleaf manzanita ( Arctostaphylos pungens K. Kunth), a regionally abundant North American shrub, in relation to the wide spectrum of behaviours displayed by its flower-visiting insects. We recorded A. pungens population-level flowering phenology and nectar standing crop, and con
ducted experiments documenting its breeding system, in an Arizona upland habitat in 1998 and 1999. Floral visitors were observed over 38 hr. We recorded frequencies of six foraging behaviours within and among individuals of each visitor species. Arctostaphylos pungens flowers in late winter. During this period it is the only abundant floral resource for a diverse array of generalist insects in its habitat. We observed 1206 floral visits by 46 taxa. Most floral visitors pursued mixed behaviours: at the species and/or individual level, they foraged both legitimately and as nectar-robbers or thieves. The most commonly mixed behaviours were legitimate pollen collection (which likely resulted in pollen transfer) and secondary nectar-robbing (which was highly unlikely to do so). As A. pungens was found to be largely self-incompatible, robbing and thieving visits should be detrimental to reproductive success. Although theoretical analyses often assume that exploiters must be punished or excluded for mutualism to persist evolutionarily, exploitation is in fact ubiquitous within cooperative interactions in nature. In manzanita, very few floral visitor species could be classified as exclusively beneficial or detrimental to plants: rather, they exhibited multiple foraging strategies, with no evidence of plant control. Such pollinator-nectar robber spectra appear to be common, and constitute an important challenge to current understanding of how mutualism can persist. Normal 0 21 false false false DE X-NONE X-NONE NOTE: Supporting information to this article may be found in the left menu.
Low fruit set, despite normally-developed flowers, is often a significant contributor to poor yield of the self-fertile sour cherry (Prunus cerasus ) cultivar ‘Stevnsbaer’ in Denmark. The aim of this study was to investigate the effect of insect, and particularly, bee pollination on the fruit set of this cultivar, in order to provide orchard management information for both Danish ‘Stevnsbaer’ growers and beekeepers. Visits to cherry flowers by honey bees ( Apis mellifera), Bombus species and sol
itary bees, were recorded during the flowering of ‘Stevnsbaer’ in five separate Danish orchards. The results indicate that there is a significantly higher fruit set on open pollinated branches when compared to caged branches, where bees and other pollinating insects where excluded. The results were qualitatively consistent over three different seasons (2007, 2009 and 2010). A period of prolonged cold, humid weather before and during early flowering probably reduced fruit set significantly in 2010 compared to 2009. Regarding the apparent benefits of bee pollination on fruit set and subsequent implications for yield, we recommend placing honeybees in ‘Stevnsbaer’ orchards during flowering to sustain commercially viable production. Another valuable management strategy would be to improve foraging and nesting conditions to support both honey and wild bees in and around the orchards.
Science has shown the importance of animal pollinators to human food security, economy, and biodiversity conservation. Science continues to identify various factors causing pollinator declines and their implications. However, translation of the understanding of pollinators’ roles into current policy and regulation is weak and requires attention, both in developed and developing nations. The national and international trade of commodities generated via insect pollination is large. Trade in those
crops could be a means of influencing regulations to promote the local existence of pollinating species, apart from their contributions to biodiversity conservation. This paper, using the example of international coffee production, reviews the value of pollinating species, and relates them to simple economics of commodity production. Recommendations are made that could influence policy and decision-making to promote coffee production, trade, and pollinators’ existence. Assumptions and considerations are raised and addressed. Although the role of insect pollinators in promoting fruit set and quality is accepted, implementing pollination conservation in forest habitats may require assured higher prices for coffee, and direct subsidies for forest conservation to prevent conversion to other crop lands. Exporting and importing governments and trade organizations could establish policy that requires insect pollination in the coffee certification process. The European Parliament and the North American Free Trade Agreement could be instrumental in creating policy and regulation that promotes insect pollination services in coffee production. The reciprocity between the services of insect pollinators in certified coffee production and their services in forest biodiversity production should be implicit in future policy negotiations to enhance both systems.
We developed novel artificial flowers that dispense and receive powdered food dyes as pollen analogues while their nectar is replenished by capillary action. Dye receipt, which can be measured colourimetrically, is a direct surrogate for pollen receipt or female reproductive success, but can also serve to compare pollen donation (male reproductive success) from flowers with different colours of dye. By allowing captive bumble bee colonies to visit large arrays of such flowers, we investigated wh
ether total dye receipt depended on the sugar concentration of a flower’s nectar. Estimating pollen transfer, rather than simply visitation rate, is appropriate for this question because flowers with more concentrated nectar might accrue more pollen not only through higher visitation rates but also through longer visits that transfer more pollen per visit. Flowers with richer nectar did receive more dye regardless of their spatial arrangement, but the effect was greatest when rich and poor flowers were segregated in large blocks, as opposed to being intermingled.
Many studies in the past decade, mostly in temperate countries, have documented the effects of habitat loss and fragmentation on species richness, composition, and abundance and the behaviour of pollinators. Changes in landscape structure are considered to be the primary causes of the limitation of pollination services in agricultural systems. Here, we review evidence of general patterns as well as gaps in knowledge that could be used to support the development of policies for pollinator conserv
ation and the restoration of degraded landscapes. Our results indicate a recent increase in the number of studies on the relationships between pollination processes and landscape patterns, with some key trends already being established. Many authors indicate, for example, that the spatial organization of a landscape has a great influence on the survival and dispersal capacity of many pollinators, as spatial organization affects resource availability and determines the functional connectivity of the landscape. Additionally, the shape, size and spatial arrangement of the patches of each type of natural environment, as well as the occurrence of different types of land use, can create sites with different degrees of connectivity or even barriers to movement between patches, which can deeply modify pollinator flows through the landscape and consequently the success of cross-pollination. However, there are still some gaps, such as in the knowledge of which critical values of habitat loss can lead to drastic increases in pollinator extinction rates, information that is needed to evaluate at what point plant-pollinator interactions may collapse. We also need to concentrate research effort on improving a landscape’s capacity to facilitate pollinator flow (connectivity) between crops and nesting/foraging areas.
Apple production in the UK is worth over £100 million per annum and this production is heavily dependent on insect pollination. Despite its importance, it is not clear which insect pollinators carry out the majority of this pollination. Furthermore, it is unknown whether current UK apple production, in terms of both yield and quality, suffers pollination deficits and whether production value could be increased through effective management of pollination services. The present study set out to add
ress some of these unknowns and showed that solitary bee activity is high in orchards and that they could be making a valuable contribution to pollination. Furthermore, fruit set and apple seed number were found to be suffering potential pollination deficits although these were not reflected in apple quality. Deficits could be addressed through orchard management practices to improve the abundance and diversity of wild pollinators. Such practices include provision of additional floral resources and nesting habitats as well as preservation of semi-natural areas. The cost effectiveness of such strategies would need to be understood taking into account the potential gains to the apple industry.
Brown’s peony, Paeonia brownii (Paeoniaceae), is one of only two peony species native to the Western Hemisphere, yet its pollination ecology and breeding system have never been documented. Using flowering individuals of an endemic colony in the Blue Mountains of Oregon, U.S., we investigated the peony’s pollination system and floral function. We also examined pollen/carpel interactions through experimental pollinations aided by fluorescence microscopy. Paeonia brownii appears to be self compatib
le and mostly protogynous with floral traits of a generalist pollination system. The flowers appear to attract insects by producing abundant floral nectar secreted from lobes of a perigynous disc throughout their 9-15-days of anthesis. The most common pollen vectors were wasp queens (Vespidae), the large flower fly Criorhina caudata (Syrphidae), and females of Lasioglossum spp. (Halictidae), all of which foraged exclusively for nectar. Whether collected from foraging wasps and flies, anthers, or stigmas, about half the pollen grains appeared fertile. The number of ovules per carpel was about 19. Seed set (seeds/ovule) of naturally pollinated flowers was about 20% with about 4 viable seeds per follicle. The number of fertile pollen grains transferred to the stigma under natural conditions was highly variable but generally low, which may have contributed in part to the low rate of seed set. This study raises further questions about the role of pollen sterility, floral nectar and vespid wasps in shaping a pollinator system that is unusual in Paeonia.
Artificial introductions of non-native species by humans can remove geographical barriers between species. In the absence of reproductive barriers, closely related introduced taxa may be able to hybridize, resulting in the formation of novel genotypes. These may be more suited to the new environment than either of their parent taxa, and have the potential to become more invasive. We investigated potential reproductive barriers between the non-native invasive Impatiens glandulifera and its less a
ggressive non-native congener I. balfourii . We examined behaviour of pollinators, including their foraging preferences and whether they switched from one species to the other. Moreover, conspecific and interspecific artificial crosses were performed between these species and seed production and the germination success of hybrid seeds were assessed. Both I. balfourii and I. glandulifera had relatively long flowering periods which mostly overlapped. Insect visitors were observed to switch from flowers of one species to the other during a single foraging bout, confirming that natural pollen transfer between species is possible. Artificial interspecific pollination resulted in the production of seeds, suggesting the presence of incomplete reproductive barriers between the two species. However, hybrid seeds mostly failed to germinate making the production of invasive hybrids unlikely. Nevertheless, because of the prolific reproductive output of these species we would not exclude the possibility that some viable hybrid seeds could be formed and become established. Further investigation of the fitness of hybrid seeds is required as hybridisation may allow Impatiens to exploit different ecological niches.
Honey bees depend on flower resources (nectar and pollen) to supply individual and colony needs. Although behavioural studies already assessed optimum foraging patterns of bumblebees, honey bees foraging behavioural patterns have been poorly assessed. We used Sysirinchium palmifolium L. (Iridaceae), a low-growing, abundant and anthophilous grassland flower to test the hypotheses that Apis mellifera workers would i) spend more time, ii) visit a greater number of flowers, and iii) travel greater d
istances within patches of S. palmifolium which were newly opened or not been visited by other pollinators when compared to foraging on patches that were available to pollinators during its whole blooming period (only one day). In two different sunny days, we measured bee activities in an area opened for visitation during the whole anthesis (OP plot treatment) and another opened for visitation only half of anthesis (CL plot treatment). We observed bees spending more time, visiting more flowers and travelling more in S. palmifolium CL treatment than the OP plot treatment. Previous studies already showed bees alter their foraging behaviour in the lack of resources. Honey bees are able to remember the period of the day when resources are usually the higher, they probably detect the most promising period to gather resources on S. palmifolium flowers. Since A. mellifera is a pollinator with a wide-distribution and is considered an important cause of changes on native pollinator communities, we support additional studies evaluating its foraging behaviours to better understand how it explores flower resources.
The foraging behaviour of pollinators can influence their efficiency in pollinating certain plant species. Improving our understanding of this behaviour can contribute to an improvement of management techniques to avoid pollination deficits. We investigated the relationship between the number of visits of bumble bees ( Bombus impatiens ) to tomato flowers ( Lycopersicon esculentum ) and two variables related to the quality of the resulting fruits (weight, number of seeds), as well as the relatio
nship between foragers’ thoracic weights, physical characteristics of thoracic vibrations (main frequency, velocity amplitude), amount of pollen removed from flowers, and the quality-related variables. In addition, we studied the capability of foragers to assess the availability of pollen in flowers. Tomato weight and seed number did not increase with the number of bee visits, neither were they correlated with the foragers’ thorax weight. Thorax weight also did not correlate with the amount of pollen removed from the flowers nor with the physical characteristics of vibration. Vibration characteristics did not change in response to the amount of pollen available on tomato flowers. Instead, foragers adjusted the time spent visiting the flowers, spending fewer time on flowers from which some pollen had already been removed on previous visits. The quantity and the production-related variables of tomatoes are not dependent on the number of bee visits (usually one visit suffices for full pollination); bigger foragers are not more efficient in pollinating tomato flowers than smaller ones; and B. impatiens foragers are capable of evaluating the amount of pollen on a flower while foraging and during pollination.
Male Eastern Olive Sunbirds ( Cyanomitra olivacea ) and Xylocopa nigrita carpenter bees in Tanzania both utilise the flowers of male plants of Lagenaria sphaerica (Cucurbitaceae) as a source of nectar. The sunbirds set up territories defending this nectar resource. Observations of interactions between the sunbirds and the carpenter bees show that the bees are aggressively displaced from flowers when spotted by the birds. Only the bees can be considered as legitimate pollinators as the birds do
not contact the anthers of the male flowers and were never seen visiting nectarless female flowers of Lagenaria sphaerica . Such territory defence may have implications for the frequency of movement and composition of pollen being transferred from male to female flowers which warrants further research.
There is growing concern that current pollinator decline will affect the reproduction of plant species, potentially driving a decline in plant population densities. We experimentally tested whether a reduction in flower visitation caused a reduction in fertilization rate in several species, and whether any reduction in fecundity of species depends on their degree of reproductive dependence on pollinators and their attractiveness for pollinators. We recorded visitation rate, fertilization rate, s
eed weight, flower size and density of nineteen insect-pollinated perennial herbs inside thirty 2 x 2 m dome-shaped cages covered with fishnet (experimental plots) and in thirty control plots in a Norwegian hay meadow. We used a bagging experiment to estimate the ability of the study species to produce seeds in the absence of pollinators. The visitation rate for fifteen of nineteen study species was lower inside cages than outside and only three of the fifteen species showed significantly reduced fertilization rates in the experimental plots. The magnitude of reduction in fertilization rate was positively related to the degree of pollinator dependence, but not to their attractiveness for pollinators or to the reduction in visitation rate. Seed weight was not affected by the experiment. The lack of an overall effect of reduced pollinator visitation on fertilization rate suggests that some species may be robust to a pollinator decline that could increase pollen limitation on plant reproduction. Our results suggest that species with greater pollinator dependence are more vulnerable to pollinator loss. NOTE: Supporting information to this article may be found in the left menu.
The tomato plant has a specific relationship with native pollinators because the form of its flowers is adapted to buzz pollination carried out by some pollen-gatherer bees that vibrate their indirect flight muscles to obtain that floral resource. The absence and the low density of these bees in tomato fields can lead to pollination deficits for crop. The aim of this study is to demonstrate that open tomato flowers, probably visited by native pollinator, have greater pollen load on their stigma
than unvisited flowers. Another objective is to show that this great pollen load increases fruit production. We selected crops of the Italian tomato cultivar in areas of the State of Goiás, Brazil. Thirty seven plants of three crops each had one inflorescence bagged in the field. Bagged and non-bagged flowers had their stigmas collected and the amount of pollen on their surfaces was quantified. For the comparison of fruit production, we monitored bagged and not-bagged inflorescences and after 40 days, their fruits were counted, weighed, measured and had their seeds counted. The amount of pollen grains on the stigma of flowers available to pollinators was higher than that on the stigma of bagged flowers. On average, fruit production was larger in not-bagged inflorescences than in bagged inflorescences. In addition, not-bagged flowers produced heavier fruits than did bagged flowers. There was a significant difference in the number of seeds between treatments, with significantly more seeds in the non-bagged fruit. Our results show that native bees buzz-pollinate tomato flowers, increasing the pollen load on their stigma and consequently fruit production and quality.
More than 70% of world’s crops benefit from biotic pollination, and bees are their main pollinators. Despite the fact that some of these insects have been broadly studied, understanding the interactions between plant crops and their pollinators with a local scale approach is necessary when aiming to apply proper protective and management measures to pollinators and their respective crops. In this context, we analyzed the pollination status of open-field tomato crops ( Solanum lycopersicum L.), r
egarding fruit-set, visitation rate and the quality of fruits. We recorded the formation of fruits through spontaneous self-pollination and open-pollination, and the occurrence of pollinators in 24 areas of open-field tomato crops. We performed experiments of apomixis, spontaneous self-pollination, manual cross pollination and supplemental cross pollination (simulating the pollinator behavior) in a greenhouse. The fruit quality was evaluated according to circumference, weight, volume and number of seeds. Higher production of fruits after open-pollination compared to spontaneous self-pollination indicates the importance of pollinators to increment productivity of S. lycopersicum in the study area. The circumference and the number of seeds from tomatoes of the greenhouse plantation did not differ between spontaneous self-pollination and the manual cross pollination. In the open-field crops the number of seeds was higher for fruits resulting from open-pollination. Our results indicate that the importance of bees is mainly related to the increase in fruit production, thus incrementing the productivity of tomato crops. production, thus incrementing the productivity of tomato crops.
The conversion rate of flowering into fruiting stems in C. montanum at two sites over four seasons was 52-85%. This is high for insect-pollinated, food mimics in this genus and greater than fruit sets recorded in populations of four species native to China and two species native to North America. Comparative measurements of the trap-like labellum of C. montanum showed it was intermediate in size compared to measurements of six other Cypripedium spp. found in North America and China. While vis
itors to flowers of C. montanum represented three insect orders, at two sites, over four seasons only small- to medium-sized, solitary bees (5-10 mm in length) carried the pollen massulae. Bee-visitation occurred at both sites and began within 24-48 hours following labellum expansion. Female bees in the genus Lasioglossum (Halictidae) were the most common carriers of massulae. However, species of visiting bees differed between sites and years. At both sites the majority of bees entered and escaped from the labellum in less than 180 seconds and there was no significant difference between the times bees spent in the flowers at both sites. At the site on the Eastside Cascades of Central Oregon, there was no correlation between the length and width of a bee and the time it spent escaping from the basal openings. There was no correlation between bee size and whether the bee carried massulae. Depending on site and year 41-58% of the bees exiting the orchids carried the orchid’s pollen. Depending on site and year 75-100% of bees collected exiting the orchids via the basal openings also carried the pollen of at least one other co-blooming species.
Interactions between invasive and native plants for pollinators vary from competition to facilitation of pollination of native plants. Theory predicts that relative floral densities should account for some of this variation in outcomes, with facilitation at low floral densities and competition at high floral densities of the invader. We tested this prediction by quantifying pollination and female reproductive success of a native herb, Geranium maculatum , in three experimental arrays that varied
in floral density of the invasive shrub Lonicera maackii : control (no L. maackii ), low floral density of L. maackii , and high floral density of L. maackii . A low density of L. maackii flowers was associated with an increase in pollinator visitation rate to G. maculatum flowers and an increase in conspecific pollen deposition compared to controls and high density arrays. Increased visitation rates were not associated with an increase in the number of visitors to low density arrays, suggesting instead that a behavioural switch in visitation within the array accounted for increased pollen deposition. In contrast, the only evidence of competition in high density arrays was a shorter duration of visits to G. maculatum flowers relative to the other treatments. The number of seeds per flower did not vary among treatments, although trends in seeds per flower were consistent with patterns of pollinator foraging behaviour. Given increased pollinator visits and pollen deposition at a low density of the invader, our study indicates that complete eradication of invasives as a management or restoration technique may have unintended negative consequences for pollination of native plants.
Yields of commercially important crops in Kenya are often far below their potential. Amongst the possible reasons for such low yields may be the ecosystem degradation that can be expected to have negative impacts on pollinator presence in cropland, and the consequent food security issue for smallholder farmers who depend on these crops for their livelihood. Our study was carried out to assess the potential pollination deficit of French beans ( Phaseolus vulgaris L.), a major export vegetable cro
p in Kenya grown by small-scale farmers. Sufficient pollination of French beans likely results in high seed set and uniform heavier green pods. Such pods get the highest grade while malformed pods are unmarketable, reducing family income. We hypothesized that pollination success was linked to the abundance and diversity of large pollinators, itself associated with the proximity to natural habitats. Flower visitors to French beans were sampled in 2011 and 2012 in ten farmer-managed plots, five within 200 m from the edge of Mt. Kenya forest and five farther away, more than 1000 m. Each plot measured 760 m 2 and was planted at the same time, with the “Julia” variety. Flowers were observed for 2 h in each plot once weekly for three weeks at peak flowering from 0900-1100 h in the morning and 1200 – 1400 h in the afternoon on alternate days. Honey bees ( Apis mellifera ) were the most abundant visitors of French bean flowers followed by carpenter bees ( Xylocopa spp.) and leafcutter bees ( Megachile spp.). Significantly higher numbers of leafcutter bees were recorded on farms far to the forest. There was no significant difference in honeybee abundance among the study sites, probably because apiaries and wild colonies are located across the landscape. French bean yield was significantly correlated with the mean abundance of carpenter bees in 2011. This suggests the possible occurrence of pollination deficit in French beans where the density of carpenter bees is insufficient, which was reflected by the high variability of yields in the farmland. We advocate that area-wide management and conservation of carpenter bees should be initiated to support French bean farming in the area.
Floral scent is likely important to the pollination of parasitic plants, despite that it has not been well-studied. We studied the pollination ecology of the North American stem holoparasite Pilostyles thurberi (Apodanthaceae) at two field sites in Texas. To identify effective pollinators, we collected floral visitors to P. thurberi flowers, observed their foraging behavior, and looked for P. thurberi pollen on their bodies. Augochloropsis metallica bees (Halictidae) and eumenine potter wasps (V
espidae) were pollinators. P. thurberi flowers are visually inconspicuous but produce a strong fruity fragrance. GC/MS analysis of whole floral extracts and dynamic headspace samples revealed the fragrance to be an unusually simple bouquet of raspberry ketone and several eugenols. Comparison of scent profiles to those from uninfected host plants ( Dalea formosa ) allowed putative separation of parasite and host volatiles. This is the first report of the constituents of floral fragrance in Apodanthaceae.
This paper comprises Part II of a review of flower visitation and pollination by Diptera (myiophily or myophily). While Part I examined taxonomic diversity of anthophilous flies, here we consider the rewards and attractants used by flowers to procure visits by flies, and their importance in the lives of flies. Food rewards such as pollen and nectar are the primary reasons for flower visits, but there is also a diversity of non-nutritive rewards such as brood sites, shelter, and places of congreg
ation. Floral attractants are the visual and chemical cues used by Diptera to locate flowers and the rewards that they offer, and we show how they act to increase the probability of floral visitation. Lastly, we discuss the various ways in which flowers manipulate the behaviour of flies, deceiving them to visit flowers that do not provide the advertised reward, and how some flies illegitimately remove floral rewards without causing pollination. Our review demonstrates that myiophily is a syndrome corresponding to elements of anatomical, behavioural and physiological adaptations of flower-visiting Diptera. The bewildering diversity of anthophilous Diptera and of the floral attractants and rewards to which they respond allows for only broad generalizations on myiophily and points to the need for more investigation. Ecological relationships between flies and flowers are critical to the survival of each group in many habitats. We require greater understanding of the significance of flies in pollination, especially in the face of recent pollinator declines.
It is increasingly recognized that a sustainable future for agriculture must build on ecosystem services. Pollination is an important ecosystem service in all agroecosystems. In much of Africa the main challenge is conserving pollinator biodiversity in traditionally “ecologically-intensive” agroecosystems that are changing to meet different demands for food security and poverty alleviation, rather than safeguarding pollination in transition from conventional agricultural systems, with a high rel
iance on purchased inputs, to “ecologically-intensive” agroecosystems using natural inputs provided by biodiversity. Priority issues for research and development in pollination services in Africa include, inter alia: quantification and documentation of pollination deficits and finding measures to address these; socio-economic valuation of pollinator-friendly practices; assessment of lethal and sub-lethal effects of farming methods, such as pesticide use, on crop pollinators; identification of habitat management practices that enhance synergies between pollinator lifecycles and crop growing patterns; and policy analysis in relation to drivers and trends in pollination services and management.
Bumblebees ( Bombus spp.) are efficient pollinators of many flowering plants, yet the pollen deposition performance of individual bees has not been investigated. Worker bumblebees exhibit large intraspecific and intra-nest size variation, in contrast with other eusocial bees; and their size influences collection and deposition of pollen grains. Laboratory studies with B. terrestris workers and Vinca minor flowers showed that pollen grains deposited on stigmas in single visits (SVD) were signific
antly positively related to bee size; larger bees deposited more grains, while the smallest individuals, with proportionally shorter tongues, were unable to collect or deposit pollen in these flowers. Individuals did not increase their pollen deposition over time, so handling experience does not influence SVD in Vinca minor . Field studies using Geranium sanguineum and Echium vulgare , and multiple visiting species, confirmed that individual size affects SVD. All bumblebee species showed size effects, though even the smallest individuals did deposit pollen, whereas there was no detectable effect with Apis with its limited size variation. Two abundant hoverfly species also showed size effects, particularly when feeding for nectar. Mean size of foragers also varied diurnally, with larger individuals active earlier and later, so that pollination effectiveness varies through a day; flowers routinely pollinated by bees may best be served by early morning dehiscence and visits from larger individuals. Thus, while there are well-documented species-level variations in pollination effectiveness, the fine-scale individual differences between foragers should also be taken into account when assessing the reproductive outputs of biotically-pollinated plants.
The large genus Calliopsis (Andrenidae, Panurginae) is composed of ten subgenera with polylectic and presumably oligolectic species. These categories have been mainly developed from floral visits of female bees collecting pollen. In the present study, pollen analyses of nest provisions and scopal loads from museum specimens of the monotypic subgenus Ceroliopoeum were carried out to assess its degree of specialization to pollen host-plants. Despite the great variability of floral resources close
to two active nest aggregations in the Chaco sites (83 and 44 melittophilous taxa from 36 and 17 families, respectively), the only host-plant recorded in all nest pollen samples was Prosopis . This genus was represented by six species and their hybrids, all having similar pollen morphology. The nesting sites in Monte scrub also contained several Prosopis species, some of which had different pollen morphology from those of the Chaco forest. Two different Prosopis pollen types were identified in all samples. Since the whole geographic distribution of C. laeta matches with the range of Prosopis , its strong association with this pollen host seems to be well supported. However, the low number of study populations (four) could erroneously indicate oligolectism. A broader sampling is necessary to ensure the character of specialization. Most Calliopsis species have been identified as oligolectic. Yet, this categorization has mainly been based on floral visits and a large diversity of floral hosts has been recorded for each bee species. Further analyses are necessary to confirm the relationship of this genus with its pollen hosts. Moreover, as most of them have short to medium phenologies (up to 4 months) their presumably oligolecty can be due to a local specialization (i.e. variable according to location) typical of polylecty. NOTE: Supporting information to this article may be found in the left menu.
The orchard crop pollinator Osmia lignaria (Hymenoptera: Megachilidae) was evaluated for apple pollination in the Annapolis Valley, Nova Scotia, Canada during 2000-2001. Resulting pollination levels (measured as pollen grains on floral stigmas), percent fruit set, mature fruit weight and seed yield were evaluated against an attempted gradient of Osmia bee density. In addition, fruit quality was assessed using two symmetry indices, one based on fruit diameter, the second on fruit height. Pollinat
ion levels, percent fruit set and mature fruit quality were much higher than minimums required for adequate crop production, and all but pollination levels showed weak but significant decreases at increased distance from the established nests, suggesting that even at low numbers these bees may have been making significant contributions to apple production. Fruit were typically of better quality in areas of the orchard adjacent to Osmia nests, having fewer empty carpels and greater symmetry; fruit quality (i.e., symmetry) is typically most reduced when two or more adjacent carpels are empty. Empty carpels reduce growth in fruit height rather than diameter, suggesting that symmetry indices using fruit diameter are not sensitive enough to evaluate fruit quality. Evidencing this, fruit without mature seeds observed in this study showed high symmetry based on diameter, but were greatly asymmetric with respect to fruit height. Further discussion on Osmia bees as apple pollinators and on methods of evaluating apple fruit quality with respect to seed distribution within the apple fruit are provided.
Wild pollinators have a positive impact on the productivity of insect-pollinated crops. Consequently, landowners are being encouraged to maintain and grow wildflower patches to provide habitat for important pollinators. Research on plant-pollinator interaction matrices indicates that a small number of “core” plants provide a disproportionately high amount of pollen and nectar to insects. This matrix data can be used to help design wildflower plantings that provide optimal resources for desirable
pollinators. Existing interaction matrices from three tall grass prairie preserves in the northern prairies were used to identify core plant species that are visited by wild pollinators of a common insect-pollinated crop, namely canola ( Brassica napus L.). The wildflower preferences of each insect taxon were determined using quantitative insect visitation and floral abundance data. Phenology data were used to calculate the degree of floral synchrony between the wildflowers and canola. Using this information I ranked the 41 wildflowers that share insect visitors with canola according to how useful they are for providing pollinators with forage before and after canola flowers. The top five species were smooth blue aster ( Symphyotrichum laeve (L.) A. & D. Löve), stiff goldenrod ( Solidago rigida L.), wild bergamot ( Monarda fistulosa L.), purple prairie-clover ( Dalea purpurea Vent.) and Lindley’s aster ( Symphyotrichum ciliolatum (Lindl.) A. & D. Löve). By identifying the most important wild insects for crop pollination, and determining when there will be “pollen and nectar gaps”, appropriate plant species can be selected for companion plantings to increase pollinator populations and crop production. NOTE: Supporting information to this article may be found in the left menu.
Preferences for certain nectar plants by moth pollinators have not been extensively studied, particularly seasonal switches in nectar diet. The genus Hemaris, found throughout North America and parts of other continents, is a useful new system to address questions of flower-insect interactions as the moths are relatively common and day-flying . In this study we address the following questions with a group of three Hemaris species. (1) Does Hemaris display a preference for foraging on the native
swamp thistle, Cirsium discolor, over the non-native invasive knapweeds, Centaurea spp.? (2) What factors might be driving Hemaris’ preferences? The bloom periods of C. discolor and Centaurea overlap in the northeastern United States, with Centaurea blooming from approximately June through September and C. discolor blooming for approximately the first three weeks of August. Hemaris typically ecloses in the first week of July and fed on Centaurea until C. discolor bloomed. We tracked and recorded Hemaris visits to both plant species. During the co-blooming period of C. discolor and Centaurea , Hemaris visits significantly more C. discolor inflorescences, demonstrating a possible preference for the native species. Hemaris reverts to nectaring at the non-native Centaurea after native C. discolor’ s bloom period ends. The nectar of C. discolor has a significantly higher sugar concentration than does the nectar of Centaurea ; this difference may account for part of the moths’ preference for C. discolor.
A major concern with endangered plants is that they might attract insufficient numbers of pollinators, produce low numbers of seeds, and decline towards extinction. We examined effects of density as it varied within populations on the pollination of Pentachaeta lyonii , an endangered species that requires pollinators for seed set. Generalist bee-flies and bees were abundant pollinators at three sites for two years. Per-capita visitation rates did not decline at sparse points or for plants placed
on the order of 10 m away from other flowering individuals. Seed production was not pollinator-limited within patches, but seed set was low beyond 10 m from neighbours. Considering prior findings, factors such as habitat loss, competition with alien plants, and poor establishment of new populations likely contribute to the rarity of P. lyonii more than pollination failure.
Plant species that share pollinators can suffer from interspecific pollen deposition. Male reproductive success is inevitably reduced by the loss of pollen to flowers of another species. Female reproductive success can be affected by reduced stigmatic area or, more strongly, through allelopathic effects by which the admixture of some foreign pollen reduces seed or fruit set. We tested for allelopathic effects of Taraxacum officinale (Asteracaeae) pollen on the seed set of montane wildflowers Ery
thronium grandiflorum (Liliaceae) and Erysimum capitatum (Brassicaceae), by hand-pollinating plants with pollen mixtures. Taraxacum is a common invasive species, which produces allelopathic chemicals in its root and vegetative tissue, making it a likely candidate for pollen allelopathy. Flowers of both species produced fewer well-developed seeds when pollinated with pollen mixtures containing Taraxacum pollen. The pollen-allelopathic potential of weedy dandelion may add to its ability to disrupt communities that it invades.
Although generalized and specialized plants are often discussed as alternative states, the biological reality may better be viewed as a continuum. However, estimations of pollinator specificity have been confounded in some studies by the assumption that all floral visitors are pollinators. Failure to account for pollen load can lead to inaccurate conclusions regarding the number of pollinators with which a species actually interacts. The aim of this study was to clarify the distribution of polli
nation-system specialization within one clade, using a more rigorous assessment of pollen flow. The genus Oenothera has long been used as a model system for studying reproductive biology, and it provides a diversity of pollination systems and a wealth of historical data. Both floral visitation rate and pollen-load analysis of sampled pollinators, combined into a metric of pollen flow, were used to quantify the pollination systems of 26 Oenothera taxa. Metric of pollinator specialization were calculated as functions of both total pollinator taxa, and as pollinator functional groups. We found that for Oenothera , the number of floral visitors highly overestimates the number of pollinators, and is inadequate for determining or predicting pollination system specialization. We found that that pollination systems were distributed on a gradient from generalized to specialized, with more pollinator-specialized plant taxa, especially when estimated using pollinator functional groups. These results are in conflict with previous studies that depict most plant species as generalists, and this finding may be related to how prior studies have estimated specialization. NOTE: Supporting information to this article may be found in the left menu.
In temperate climates, foraging resources for pollinating insects are especially important in early spring when animals emerge from hibernation and initiate annual life cycles. One habitat, protected under EU law, which provides resources for a range of pollinating insects, but has received little research attention, is fixed (grey) dunes. Fixed dunes often contain creeping willow ( Salix repens , Salicaceae), which may be an important early season resource for obligate flower visitors. We exami
ned the springtime activity of flower visitors in fixed dune ecosystems in relation to sugar concentration and composition in nectar, composition of essential amino acids in pollen, and floral abundance. We also investigated whether the presence or absence of S. repens influenced the abundance and species richness of three obligate flower visiting guilds (solitary bees, bumblebees and hoverflies) in eight sites along the eastern and southern coasts of Ireland. Higher insect visitation rates were observed to species whose nectar contained greater concentrations of glucose and fructose. Solitary bee visitation rates were related to % Essential Amino Acid (EAA) in pollen and floral species richness. Ulex europeaus , and S. repens were the most abundant flowering species, but visitation rates were not related to floral abundance. Higher abundances of bumblebees and hoverflies were discovered at sites where S. repens was present. This study raises further questions about the nutritional requirements and preferences of obligate flower visitors in fixed dune ecosystems in spring time. NOTE: Supporting information to this article may be found in the left menu.
Temporal mismatches among plants and pollinators, driven by climate change, are considered a potential cause of population declines of these mutualists. However, field studies demonstrating population declines as a result of climate-driven phenological mismatches are uncommon, and the extent to which mismatches will be a problem in the future remains unclear. We revisit predicted consequences of climate-driven phenological mismatch in plant-pollinator systems by identifying nine previously-appli
ed assumptions that are violated or insufficiently understood in real systems. Briefly, the assumptions are: (1) Dates of first-flowering (DFF) or dates of first activity (DFA) correctly describe phenology, and disparities between DFF and DFA represent the magnitude of mismatch. (2) “Optimal” matches are measured correctly. (3) Advancement of DFF or DFA will be the primary phenological change in the future. (4) Future phenological shifts will be independent for each species. (5) All plant-pollinator interactions are equally effective. (6) Populations of plants and pollinators are limited by mutualistic interactions. Some previous models have also assumed that the effects of future mismatches will not be influenced by (7) emergence of novel interactions, (8) competition or facilitation from altered co-flowering and co-flight, and (9) phenotypic plasticity and rapid adaptive evolution of phenology. Those assumptions affect the direction, extent, and accuracy of predicted consequences of future phenological mismatch. In discussing them, we identify important topics for future research in pollination ecology.
When plant species invade new areas, they can escape from specialist enemies and thereby reduce investment in chemical defense. Enemy release may have other impacts on plant chemistry; in the absence of specialists, plants may be able to increase production of volatiles that enhance attractiveness to pollinators. In the United States (US), the introduced Eurasian wild parsnip, Pastinaca sativa , has long been subject to attack by an introduced coevolved florivore, Depressaria pastinacella, the p
arsnip webworm. In 2004, webworms were found for the first time attacking parsnips in New Zealand (NZ). Relative to US P. sativa , NZ P. sativa produces lower levels of defenses but higher levels of certain floral volatiles, suggesting that escape from its specialist florivore may have resulted in changes in volatile profiles to increase pollinator attraction. In this study, we examined the influence of wild parsnip floral volatiles on pollinator attraction and seed production in NZ and the US. While many insect groups were observed on parsnip umbels, the percentage of flowers that set seed could significantly be predicted by the occurrence of large calyptrate flies and small syrphids in both localities. In the US, β-pinene, γ-terpinene, hexyl butyrate, octyl butyrate, germacrene D and an unknown monoterpene were all positively correlated with visitation by large calyptrates and small syrphids. In NZ, trans- ocimene, carene and octyl butyrate were positively correlated with visitation. Remarkably, most compounds positively associated with visitation are produced in significantly higher proportions in NZ flowers, suggesting that NZ flowers, in the absence of specialized florivores, may be chemically better constituted to attract pollinators.
Understanding the interaction between reward-seeking flower feeding animals and plants requires consideration of the dynamic nature of nectar secretion. Studies on several plants suggest that nectar secretion may increase in response to its removal, but it is not clear whether the phenomenon is widespread. We determined whether 11 species of Colorado mountain wildflowers showed removal-enhanced nectar replenishment (RENR). We measured floral phenology, nectar volumes, rate of replenishment, and
compared the cumulative nectar produced following five hourly removals with that accumulated after five hours. Nectar replenishment occurred rapidly, within minutes; statistically significant RENR was observed in 9 of our 11 study species, with the strongest effects in bee-pollinated species. We discuss the implications of RENR in plant species on the measurement of nectar, the adaptive advantage of RENR, and the energetic costs of RENR.
Analysis of the pollen associated with pollinators can reveal their role in pollination, the habitats and plants they visit, from where they migrated, what they eat, and dispersal patterns in and around cropping systems. However, finding pollen on and or in a pollinator depends on the technique used to recover the pollen. Acetolysis can be used to recover pollen from internal insect tissues (gut, alimentary canal, crop, etc.), external tissues (proboscis, legs, eyes, etc.) or both. Acetolysis is
the best technique for recovering pollen because any tissue is dissolved and lipids and debris are removed from the sample and the pollen grains. This makes the diagnostic characteristics of the pollen grains more visible so that accurate pollen identification can be made. By using the proper technique, better pollen recovery can be made and thus better data can be obtained.
This study aimed to evaluate the importance of wild bee and feral honeybee visits for cotton production on conventional and organic farms. Experiments were conducted in Brazil, on a conventional cotton farm in Mato Grosso state in the Amazon biome and on an organic farm in Paraíba state in the Caatinga biome. On the conventional farm, bee assemblage and cotton production were measured near to and far from natural vegetation. Bee richness, fibre fraction, seed number and yield (Kg/ha) were higher
by 57.14, 1.95, 17.77 and 18.44% respectively in plots near natural vegetation, but bee abundance did not vary with distance to natural vegetation. On the organic farm, because the cropping area is surrounded by natural vegetation, pollination deficit was evaluated using an exclusion experiment where cotton production of flowers bagged to prevent bee visitation (spontaneous self-pollination) was compared to production of flowers open to bee visitation (open pollination). Open pollinated flowers had higher average boll weight, fibre weight and seed number. Although cotton is not directly dependent on bee pollination, bees increased cotton production on the organic farm by more than 12% for fibre weight and over 17% for seed number. Our data confirm the importance of maintaining communities of pollinators on cotton farms, especially for organic production.
While it is well recognised that pollination is an ecosystem service of vital importance to human well-being through its role in food production, it is still remarkable how little is known, on a crop-by-crop basis, about this role, and the extent and causes of declines in the service. Without better documentation of the specific contribution of pollination to crop yields, there have been mounting - and justified - questions about how relevant pollination may be to agricultural development and fo
od security. In addition, the vast majority of studies of pollination services to crops have been carried out in Europe and North America; and certainly the problems we know to impact pollinators most severely – a high dependence on agricultural chemicals and monocropped landscapes offering little diet diversity to pollinators – are typical features of industrialised, Northern hemisphere agriculture.
Canola crop productivity is benefited by bee pollination and it has been shown that bee communities can be affected by landscape composition. The aim of this study was to analyse the bee community and its relationship to canola seed production in agricultural areas. The density, abundance and richness of floral visitors of Brassica napus cultivar Hyola 61 in six commercial fields in southern Brazil were studied, and their relationships with seed production and the ratio of semi-natural, forested
and agricultural areas surrounding the crops were examined. It was observed that canola fields of southern Brazil are surrounded by a homogeneous landscape dominated by agricultural areas. The survey of bees detected a low abundance and richness of native bees in contrast to the high abundance of Apis mellifera . Except for a negative correlation between the abundance of honey bees and the proportion of forested areas within a 2000 m radius from the field (R = -0.90; P = 0.012), no other correlations were found among bee abundance and richness and landscape composition. Although there was not a relationship between A. mellifera and seed set, there was a positive correlation between insect density and seed weight per plant (R = 0.87; P = 0.024). As honey bees were the most captured insect (79%), much of the pollination in this system was probably achieved by honey bees.
Pollination deficit could cause low yields in cashew ( Anacardium occidentale ) and it is possible that deforestation surrounding cashew plantations may prevent effective pollinators from visiting cashew flowers and contribute to this deficit. In the present work, we investigated the proximity effect of small and large forest fragments on the abundance and flower visits by feral Apis mellifera and wild native pollinators to cashew flowers and their interactions with yield in cashew plantations.
Cashew nut yield was highest when plantations bordered a small forest fragment and were close to the large forest fragment. Yield from plantations that did not border small forest fragments but were close to the large forest fragment did not differ to yield from plantations at a greater distance to the large forest fragment. Flower visits by wild native pollinators, mainly Trigona spinipes , were negatively affected by distance to the large forest remnant and their numbers were directly correlated to nut yield. The number of A. mellifera visiting cashew flowers did not change significantly with distance to forest fragments, nor was it correlated with yield. We conclude that increasing the number of wild pollinator visits may increase yield, and proximity to large forest fragments are important for this.
The use of Africanised honeybee ( Apis mellifera scutellata Lepeletier) hives to increase pollination success in apple orchards is a widespread practice. However, this study is the first to investigate the number of honeybee hives ha -1 required to increase the production of fruits and seeds as well as the potential contribution of the stingless bee Mandaçaia ( Melipona quadrifasciata anthidioides Lepeletier). We performed tests in a 43-ha apple orchard located in the municipality of Ibicoara (1
3º24’50.7’’S and 41º17’7.4’’W) in Chapada Diamantina, State of Bahia, Brazil. In 2011, fruits from the Eva variety set six seeds on average, and neither a greater number of hives (from 7 to 11 hives ha -1 ) nor a greater number of pollen collectors at the honeybee hives displayed general effects on the seed number. Without wild pollinators, seven Africanised honeybee hives ha -1 with pollen collectors is currently the best option for apple producers because no further increase in the seed number was observed with higher hive densities. In 2012, supplementation with both stingless bees (12 hives ha -1 ) and Africanised honeybees (7 hives ha -1 ) provided higher seed and fruit production than supplementation with honeybees (7 hives ha -1 ) alone. Therefore, the stingless bee can improve the performance of honeybee as a pollinator of apple flowers, since the presence of both of these bees results in increases in apple fruit and seed number.
Studies of pollinator foraging behaviour often require artificial flowers that can refill themselves, allowing pollinators to forage for long periods of time under experimental conditions. Here I describe a design for inexpensive flowers that can refill themselves upon demand and that are easy enough to set up and clean that they can be used in arrays of 30 or more flowers. I also summarize of a variety of artificial flower designs developed by other researchers.
In their response to Ollerton et al.’s (2015) cautions about methods used by Rosas-Guerrero et al. (2014) to test the pollination syndromes, Aguilar et al. (2015) criticize an earlier paper by Ollerton et al. (2009). Here we respond to their concerns.
Pollination of plants by non-flying mammals, such as mice (Rodentia), is a rarely observed phenomenon. Previously, elephant-shrews (Macroscelidea), small African mammals looking similar to mice, but not being related to them, were believed to be purely insectivorous and occasional flower visits of elephant-shrews in captivity were interpreted as a by-product of the search for insects. Only recently it was demonstrated that under lab conditions elephant-shrews regularly lick nectar from flowers.
However, field observations of flower-visiting elephant-shrews and their role as pollinators were completely missing. Here I present the first evidence for flower visits and nectar consumption for elephant-shrews in the field. With video camcorders and infrared lights I recorded Cape rock elephant-shrews ( Elephantulus edwardii ) beside Namaqua rock mice ( Micaelamys namaquensis ) visiting flowers of the Pagoda lily ( Whiteheadia bifolia , Asparagaceae) under natural conditions in the Namaqualand of South Africa. With their long tongues, the elephant-shrews visited the flowers non-destructively, definitely licking nectar, but not eating insects. The footage clearly shows that the elephant-shrews’ fur around their long noses touches the pollen-sacs and the stigmas of the flowers and that the animals’ fur is being dusted with pollen. As the elephant-shrews visited several flowers of different plants, it is obvious that they transfer pollen between the plants. This observation contributes to the knowledge about the behaviour of these representatives of a unique clade of small African mammals – especially in their natural habitat. With their behavioural and anatomical uniqueness, it is not unlikely that elephant-shrews even play a role as selective force driving floral evolution. Appendices: Additional supporting information is to be found: Appendix I. With its long tongue Elephantulus edwardii licks nectar from Whiteheadia bifolia flowers, getting dusted with pollen on its nose. Infrared video. http://www.pollinationecology.org/user-files/ JPE349_Appendix1.mp4 Appendix II. Micaelamys namaquensis licking nectar from Whiteheadia bifolia flowers, getting dusted with pollen on its nose. Infrared video. http://www.pollinationecology.org/user-files/JPE349_Appendix2.avi Appendix III. Micaelamys namaquensis feeding on pollen-sacs of Whiteheadia bifolia flowers. Infrared video. http://www.pollinationecology.org/user-files/JPE349_Appendix3.avi
We investigated levels of pollinator dependency and pollinator visitation rates to flowers of six vegetable crops: brinjal (aubergine), tomato, chilli pepper (Solanaceae), okra (Malvaceae), bitter and snake gourds (Cucurbitaceae) in six small family farms in the Coimbatore region of southern India. We tested the null hypothesis that fruit set in these crops would be independent of pollinators. We assessed fruit set through self and cross pollination by pollen augmentation, by pollinator exclusio
n and open pollination. We evaluated pollen limitation by comparing percentage fruit set by hand outcrossed pollen with open pollination; pollinator dependency by differences in percentage fruit set by open pollination and autogamous pollination; and visitation rates to flowers by pollinating insects. Tomato, chilli and okra produced self-compatible hermaphrodite flowers, with higher levels of autogamous fruit set (32-76%) and significantly lower levels of pollinator dependency (0-37%), whereas andro-monoecious brinjal and monoecious gourds had significantly lower levels of fruit set through autogamy, and higher levels of pollinator dependency. Pollen limitation was not evident in any crop. Diverse pollinating insects visited the flowers, and the frequency of visits by different pollinator taxa differed with crop type. Native vegetation and uncultivated land may enhance pollinator diversity in small farms.
"Pollination syndromes" are specific combinations of floral traits that are proposed to evolve convergently across angiosperm lineages in response to different types of animal pollinators. In spite of their long history, pollination syndromes have not been tested adequately–they rarely have been examined critically to determine how well they describe floral trait diversity or predict pollinators. In a recent meta-analysis of data from the literature, Rosas-Guerrero et al. (2014) provide a welcom
e test that draws on insights from past studies. At the same time, their study illustrates several difficulties of meta-analysis approaches in general, and for pollination biology in particular. Here we discuss those difficulties and propose some solutions. We first consider how to gather studies from the literature without introducing unintended bias, such as the old-fashioned method of working backward from cited literature. We next consider how to deal with difficulties that invariably arise when extracting and analyzing often-incomplete information from heterogeneous studies. Finally we discuss issues of interpreting and presenting the results in the most informative manner. We conclude that although Rosas-Guerrero et al. (2014) and other studies such as Ollerton et al. (2009) have arrived at different conclusions about the utility of pollination syndromes, their results are not necessarily incompatible.
A quarter millennium of the changing face of pollination biology from 18th Century discovery (thesis) to 21st Century crisis is presented in six overlapping, interdigitating facets. Pollination biology was not regarded as serious science at its onset, but acceptance of the Darwinian theory of evolution has shown its biological value. Disciplinary issues in pollination (i.e. deconstruction) have produced a wealth of knowledge but with botanical and zoological solitudes. At the same time botany an
d zoology tend to be separate within agronomy and apiculture. Philosophical, social, scientific, technical, political and business agendas have variously hampered, and continue to hamper, objective science in each facet. Nevertheless, interdisciplinary approaches to pollination ecology, its inherent co-evolutionary principles, and the current “pollination” crisis have become a scientific and social unifying force that cannot but lead to new knowledge, insights and, I hope, wisdom (new synthesis).
The aquatic macrophyte Stratiotes aloides L. is of conservation concern in central Europe due to its high importance for biodiversity in lowland floodplain and ditch ecosystems. However, over the last decades this species has shown population declines for instance in Germany or the Netherlands. S. aloides is dioecious with male and female individuals, in mixed or separated stands, often reproducing vegetatively. Generative reproduction is observed less frequently, but of great importance for dec
lining plant populations facing threats of habitat destruction and eutrophication. Precisely which arthropods transfer S. aloides pollen was previously unknown. We examined flower visitors of S. aloides in the 2011 and 2014 flowering seasons in ditches of a wet grassland ecosystem in Bremen, Northwest Germany. Hydrellia tarsata Haliday (Diptera: Ephydridae) was found abundantly in male and female flowers of S. aloides in both years. Pollen of S. aloides was actively transferred by H. tarsata and reproduction of the fly in S. aloides leaves was detected by rearing H. tarsata from extracted puparia. The mining Hydrellia were parasitised by the braconid wasps Chaenusa “ punctulata ” Burghele and Chorebus “ densepunctatus ” Burghele, which also visited S. aloides flowers in 2011 and 2014. These results point to a mutualism between S. aloides and the ephydrid H. tarsata , with both partners benefiting with their own reproduction. This relationship between plant and dipteran pollinator is however complicated in a tritrophic interaction with the braconid parasitoids, which infest the mining stages of the ephydrid flies and could potentially also transfer S. aloides pollen.
Accurate records of floral visitors are critical for understanding plant pollinator interactions. However, to date, sampling methods are constrained to short sampling periods and may be subject to observer interference. Thus, complete records without sampling bias are rare. We use a portable time-lapse digital video camera to capture near-complete records of visitors to flowers over their entire blooming period. We show the broad applicability of this method by filming a wide variety of flowers
of different shapes and inflorescence types. We test the importance of long-term records by studying visitors to Cornus canadensis (bunchberry dogwood). Visitors to C. canadensis filmed simultaneously at four different sites show variation (both in rates and taxa) between inflorescences, between sites, throughout the day, and throughout the season. For C. canadensis our films also provide a record of pollen placement (an indirect measure of male fitness) and fruit set (female fitness). This technique provides near complete records of floral visitors, is likely to capture rare events, and allows simultaneous long-term filming. These results emphasize the importance of both long-term data collection and simultaneous recording at multiple sites for pollination studies. NOTE: Supporting information to this article may be found in the left menu.
The feeding habits of thrips on plant tissue, and their ability to transmit viral diseases to their host plants, have usually placed these insects in the general category of pests. However, the characteristics that make them economically important, their high abundance and short- and long-distance movement capability, may also make them effective pollinators. We investigated this lesser-known role of thrips in pointleaf manzanita ( Arctostaphylos pungens ), a Southwestern US shrub. We measured t
he abundance of three species of thrips ( Orothrips kelloggii , Oligothrips oreios , and Frankliniella occidentalis ), examined their pollen-carrying capability, and conducted an exclusion experiment in order to determine whether thrips are able to pollinate this species, and if they do, whether they actually contribute to the reproductive success of the plant. Our data suggest that indeed thrips pollinate and do contribute significantly to reproductive success. Flowers exposed to thrips only produced significantly more fruit than did flowers from which all visitors were excluded. The roles of thrips as antagonists/mutualists are examined in the context of the numerous other floral visitors to the plant.
We developed a simple restraining chamber to hold captured bumble bees temporarily so they could be photographed in the field using inexpensive “point-and-shoot” digital cameras. The process is quick, and the resulting “digital voucher” images allowed us to correct a substantial fraction of field identifications based on visual inspection. The system can improve the accuracy of monitoring programs in which it is undesirable to kill specimens to provide traditional vouchers.
Polygamomonoecy – the occurrence of perfect flowers alongside staminate and pistillate ones – in the monoecious biodiesel plant Jatropha curcas L. was reported as rare and often dismissed as having no specific functionality. Here we report that the incidence of perfect flowers is almost exclusively limited to a short period at the beginning of the blooming season and is directly associated with stigmas bending over fertile anthers, as early as in the mature bud stage. All perfect flowers have be
nt stigmas, while this trait is completely absent from female flowers produced later in the blooming season. In light of this species’ self-compatibility, we suggest that the occurrence of perfect flowers with bent stigmas promotes automatic self-pollination, thus enhances reproductive success when conditions are unfavourable for pollination.
Diptera are important flower visitors and pollinators for many plant species and in a variety of habitats. Although Diptera are not as well studied as other groups of pollinators, there is a growing literature that we review here about the ecology of their foraging behaviour and their effectiveness as pollinators. We consider (1) how their foraging is constrained by the interaction among body size, colour, and environmental factors such as temperature, humidity, wind, and light; (2) what is know
n about their foraging at scales ranging from their movements between flowers on a plant, between individuals in a population, and among species in a community (i.e., constancy); and (3) the evidence for effects of intra- and interspecific competition on foraging. We conclude with a discussion of the effectiveness of Diptera as pollinators. The available data suggest that Diptera exhibit many of the same foraging behaviours as other flower visitors and that they are effective pollinators in both natural and agricultural ecosystems.
Eonycteris spelaea is recognized as the principal pollinator of most chiropterophilous plants in SE Asia. The present study describes its feeding behaviour and clarifies its role in cross pollinating these highly self-incompatible plants. Ten individuals of E. spelaea were radio-tracked during the flowering period of durian ( Durio zibethinus ) and petai ( Parkia speciosa ) in an agricultural mosaic in southern Thailand. Eonycteris spelaea makes a mean of seven visits per hour to these trees and
80-86% of each feeding bout involves visits to multiple conspecific trees. During each visit, 93% of D. zibethinus stigmas and 50% of P. speciosa stigmas were loaded with conspecific pollen. Eonycteris spelaea was the most common bat visitor to the trees. High visitation frequency and conspecific pollen deposition by E. spelaea to D. zibethinus and P. speciosa indicates that this nectarivorous bat is an effective pollinator. Mixed planting of chiropterophilous trees in fruit orchards is recommended to ensure regular visits of E. spelaea . Protecting natural roost caves of E. spelaea is also essential in order to maintain the vital ecosystem service provided by these bats.
This study investigates the reproductive biology of, and effect of heterospecific pollen from introduced Euphorbia esula on, Linum rigidum , an annual plant native to western and central North America. Breeding-system studies revealed that L. rigidum is self-compatible, with similar pollination success, fruit set and seed set for flowers pollinated with self or outcrossed pollen. Untreated flowers not exposed to pollinators set seed, albeit at a lower rate than hand-pollinated flowers, indicatin
g that L. rigidum can autonomously self pollinate. Experiments investigating whether heterospecific pollen transfer from E. esula interferes with pollination of L. rigidum indicated that large amounts of heterospecific pollen receipt 2 - 4 hours prior to conspecifc pollen receipt reduced fruit and seed production, but that small amounts of heterospecific pollen or larger amounts received immediately prior to conspecific pollen did not affect reproduction. Pollen of E. esula was observed to germinate on and penetrate into L. rigidum stigmas and styles. Nevertheless, Euphorbia esula is unlikely to interfere with L. rigidum ’s reproduction because L. rigidum is self-compatible, capable of autonomous self-pollination, and unaffected by receipt of small amounts of Euphorbia pollen.
The reproduction of the shrub Adolphia infesta was studied in a population included in a Mexican agricultural landscape with small, cultivated plots and fragments of natural habitat. Adolphia infesta had reproductive traits consistent with those known for its tribe Colletieae, including small zoophilous flowers exposed to both xenogamous, geitonogamous and visitor-facilitated intrafloral pollination, with selfing being at least partially hindered by self-incompatibility. Visual and olfactory cue
s, together with easily accessible rewards (nectar and pollen), explain the diversity (68 species of 29 families) of insects attracted to the flowers. However, only a small subset can be considered potential pollinators (honeybee and three muscoid flies). In late floral development, pedicel bending brings the developing fruit to an upright position, which might later optimise explosive seed dispersal. The finding of this trait in A. infesta makes fruit erection a synapomorphy of the Adolphia – Discaria – Kentrothamnus clade of the tribe Colletieae. At the study site, A. infesta played a significant role as food source for the local anthophilous insect community, and through its flower visitors, the plant was indirectly connected to 11 other plant species. Knowledge derived from community studies should be applied in conservation initiatives directed at enhancing farmers’ appreciation of extant local biodiversity.
Pollen effect is important on several kernel traits in maize breeding and may vary under different pollination treatments. Our objectives in this study were i) to evaluate the effects of pollination treatments that are commonly used in maize breeding, on several ear and kernel traits, ii) to investigate if the genotypes so called “specialty corn” do have any different reaction to the pollen effect. A field trial was carried out at Dardanos Research and Application Center of Çanakkale Onsekiz Mar
t University, Turkey, in 2013. The experiment used a split plot design with three replicates. Four parents (three inbreds and one open pollinated landrace) were used as plant material. Three pollination treatments (open pollination, self-pollination and bulk pollination) were applied, and individual pollen effect of each parent on other parents was investigated. For this purpose, several ear and kernel traits (ear weight, kernel weight, kernel number, mean kernel weight) and biochemical features (protein, oil, carbohydrate and carotenoid content) were measured on harvested samples. The results showed that pollination treatment affected the variation on all traits except for oil content ( P < 0.05). Self-pollination caused a significant reduction in kernel development. Pollen effect was found significant for most traits and this effect was evident on the related genotypes with open pollinated landrace. Results indicate that pollen effect is an important factor on kernel and ear development in small plot trials, where different types of maize are grown together.
The pollination biology of the Australian endemic species Passiflora herbertiana ( Passiflora subgenus Decaloba, supersection Disemma, section Disemma ) was investigated in a single population growing in the Witches Falls section of Mount Tamborine National Park, Queensland. Three native honeyeaters were observed at the flowers, including Lewin’s Honeyeater ( Meliphaga lewinii ), the Noisy Miner ( Manorina melanocephala ), and the Eastern Spinebill ( Acanthorhynchus tenuirostris ). Visitation be
gan at 07:30 and ended by 15:30 each day. The most frequent visitor was Lewin’s Honeyeater. Flowers typically began anthesis in the afternoon, with a small number of flowers opening in the early morning. Flowers remained open between four and five days, even after successful pollination. Both the age of the flower and the amount of sun exposure were determined to affect perianth colour change from pale yellow to salmon-pink. Andromonoecy was observed infrequently in the population; most plants exhibited bisexual flowers, but a small number of individuals exhibited both hermaphroditic and male flowers with short styles held permanently erect. Controlled hand pollinations indicated that P. herbertiana is self-compatible but is not autogamous. Pollen tubes required at least 48 hours to reach the most apical ovules within the ovary. These data provide new insights into the evolution of ornithophily in the Old World Passiflora. Link to Appendix 1 : Video showing Lewin’s Honeyeaters visiting various P. herbertiana flowers
In a recent literature review, we demonstrated that the evolution of floral traits is driven by adaptation to the most effective pollinators. In a critique of this study, Ollerton et al. 2015 claimed there were apparent flaws with data collection, analyses and interpretation of results. We disagree since many of OLT´s observations and recommendations are subjective and overlook basic aspects of meta-analysis. Here, we address the main criticisms of Ollerton et al 2015.
In the neotropics, dimethyl disulphide (DMDS) is innately attractive to flower-visiting bats, and acts as a powerful bat lure in the scent bouquets of many bat-pollinated flowers. At first, DMDS appeared to be part of a general bat pollination syndrome. However, DMDS is absent in many bat-pollinated flowers of West Africa, and it is unclear whether palaeotropical flower-visiting bats are also attracted to it. Furthermore, DMDS was previously observed in neotropical, but not palaeotropical, popul
ations of Ceiba pentandra (Malvaceae, Bombacoideae). We tested for an attraction to DMDS in the most common flower-visiting bat in Thailand, the dawn bat Eonycteris spelaea . We gave bats choices of Ceiba pentandra flowers, where one random flower was scented with DMDS. Rather than preferring the DMDS-treated flower, 21 of 22 bats chose an untreated flower, showing no attraction to DMDS. Alongside past evidence, this result suggests that the role of DMDS in bat pollination syndromes may result from an adaptive convergence that is limited to the neotropics. This hypothesis could be tested through comparative studies of (1) attraction across bats, (2) floral DMDS presence across bat-pollinated plants in Asia, and (3) floral DMDS measures across New and Old World populations of Ceiba pentandra.
Identifying the pollinators of Rhododendron species is of great interest due to potential conservation threats in the native range of the genus, but the pollinators of species in Rhododendron subgenus Hymenanthes section Pontica subsection Neriiflora are unknown. Bees (Hymenoptera; family Apidae) are thought to be the pollinators of many Rhododendron species; however, species in subsection Neriiflora have ornithophilous floral morphology. We studied R. floccigerum (subsection Neriiflora ) to det
ermine the identities of visiting, potentially pollinating, and robbing species through in-person and time lapsed camera trap observations. We compared floral morphological characteristics of R. floccigerum with visitor morphological measurements to determine if visitors could fit inside the corolla. Thirteen species were observed visiting R. floccigerum (two insects, two mammals, and nine birds) and this study provides the first empirical evidence of both bird and mammal visitors to Rhododendron species. We determined that the following species are potential pollinators: Bombus sp. (an insect genus), Aethopyga gouldiae , Garrulax affinis , Heterophasia melanoleuca , and Yuhina diademata (all bird species), and we suspect that Apis sp. (an insect genus), Dremomys pernyi , Tamiops swinhoei (two mammal species), Minla ignotincta , M. strigula , Parus major , and Phylloscopus affinis (four bird species) likely rob R. floccigerum . All visitors were able to fit their heads/bodies into the corolla. We also found that though predation is frequent, the number of robbers and variety of robbing methods is unlikely to contribute to floral morphological evolution or speciation. Further understanding of the pollination biology of species in subgenus Hymenanthes will allow for effective conservation.
Many flowering plants engage in mutualistic interactions with animals in order to sexually reproduce, exchanging food rewards such as nectar and pollen for the service of pollen transfer between flowers. Floral reward variation strongly influences visitation patterns of both pollinating mutualists and non-mutualist consumers, with consequences for both male and female components of plant reproductive success. Despite the importance of pollination to ecological systems, the pollination ecology of
many plants is poorly known. At seven sites over three years, we studied the mating system, floral visitors and pollen limitation of turtlehead ( Chelone glabra L.), an eastern North America wetland herb. We found that the plant is autogamous, but requires pollinator visitation to set seed. C. glabra flowers are protandrous, with floral rewards that vary between male and female sex phases. We found diurnal variation in reward presentation that was a function of both floral phenology and consumer behavior. Bombus vagans Smith, the most common visitor to C. glabra flowers, removed a large fraction of available pollen (>36%) in single visits to newly opened flowers, and compared to other flower visitors, passively transported more pollen on flights between flowers and deposited more to conspecific stigmas, suggesting it was the most effective pollinator. The solitary bee Hylaeus annulatus L. made frequent visits to flowers, but contributed little to pollination due to morphological mismatch and because it avoided male-phase flowers. Despite high bee visitation rates, flowers were pollen limited for seed production, possibly indicating a negative effect of non-pollinating flower visitors on plant reproductive success.
As bee populations continue to decline, farmers face possible crop failures due to insufficient pollination. Crops, however, vary in the degree to which they depend on pollinators, suggesting that some crops may not be as sensitive to variation in pollinator availability and/or abundance as others. The objective of this study was to determine the contribution of biotic and abiotic factors to cranberry pollination. We performed field and greenhouse experiments to compare the effect of biotic (i.e
., bee or hand pollination) and abiotic (i.e., wind, agitation) factors on yield. We found that even in the absence of bees, cranberry is able to produce a significant yield. In the field, plants in the abiotic treatments produced higher yields (wind 230 bbl/ac [barrels per acre], agitation 200 bbl/ac) than the closed control treatment (108 bbl/ac), although these yields were not as high as the open, biotic treatment (367 bbl/ac). This corresponds to a contribution of 41% by bees, 30% by non-bee insects, and 29% by mechanical agitation. In the greenhouse, the agitation treatment had, on average, higher berry weight per upright (0.6 g/upright) than the undisturbed control treatment (0.04 g/upright), but again, not as high as the biotic treatment (3.0 g/upright). This confirmed that cranberry does not autogamously self-pollinate indicating that all yields are due to biotic or abiotic vectors moving pollen between flowers. Although bees clearly contribute to cranberry pollination, previous studies have understated the contribution of alternative mechanisms by which cranberry pollen can move between flowers.
Floral scents serve multiple functions in the interactions with organisms. Flowers of Achillea millefolium (Asteraceae) emit scent bouquets dominated by terpenoids. These flowers are mainly visited by flies and beetles, whereas bumblebees, common visitors at other Asteraceae, are absent from A. millefolium flowers. In order to test how a reduced mono- and sesquiterpenoid emission affect insect behaviour we inhibited the biochemical pathways towards the production of terpenoids of A. millefolium
plants and conducted behavioural choice tests. The inhibition resulted in reduced emission rates of most mono- and sesquiterpenes and thus altered the olfactory phenotype of the flowers. In a flight cage, flies usually chose flowers with a natural scent bouquet, bumblebees clearly preferred flowers treated with inhibitors. These findings confirm that floral scents play a pronounced role in foraging decisions of flower visiting insects and support the notion that responses towards scent are animal species-specific emphasising the role of scents as floral filters.
Bilateral symmetry has evolved from radial symmetry in several floral lineages, and multiple hypotheses have been proposed to account for the success of this floral plan. One of these hypotheses posits that bilateral symmetry (or, more generally, a reduced number of planes of floral symmetry) allows for more precise pollen placement on pollinators. Greater precision would maximize the efficacy of pollen transfer to conspecifics, while minimizing reproductive interference amongst plant species. D
espite the intuitiveness of this hypothesis, it has little experimental support. Here, we tested whether a reduction in the number of floral planes of symmetry (as in the transition from radial to bilateral symmetry) increases the potential precision of pollen placement. We analyzed video recordings of bumblebees ( Bombus impatiens ) visiting artificial flowers to determine whether consistency in flower entry angle differed between radial (round) and disymmetric (rectangular) “flowers”. We observed more consistent entry angles for disymmetric flowers than for radial flowers, with entry angles to radial flowers 43% more variable on average (standard deviations of 30° vs. 21°). Bees trained on flowers with an intermediate (square) morphology exhibited a slight, non-significant preference for radial symmetry over disymmetry. Our results show that disymmetry—an evolutionarily intermediate form of floral symmetry—has the potential to increase pollen transfer to conspecific stigmas, relative to radial symmetry. Thus, evolutionary reduction in the number of planes of floral symmetry likely provides benefits in terms of pollen delivery, as suggested by the pollen-placement-accuracy hypothesis. These findings offer insight into the evolution of floral symmetry.
Pollen assemblages from managed hives of the Australian social stingless bee Tetragonula carbonaria were examined for the presence of the threatened species Grevillea parviflora subsp. Parviflora. Managed hives of Tetragonula carbonaria were placed in bushland at Lake Macquarie, New South Wales, Australia, in four known populations of Grevillea parviflora subsp. parviflora through the main flowering period of 12 September to 2 November 2014. Samples of honey and propolis were collected from the
hives at the end of this period and analysed using palynology techniques for the presence of Grevillea parviflora subsp. parviflora pollen. Grevillea parviflora subsp. parviflora pollen was detected in all propolis samples from the four study sites but was not found in the honey samples. Field observations identified that honeybees were the dominant insect visitor to Grevillea parviflora subsp. parviflora at all sites. There were no sightings of Tetragonula carbonaria foraging on Grevillea parviflora subsp. parviflora inflorescences during field observations. This study also demonstrates the application of managed hives of the Australian stingless bees Tetragonula carbonaria for monitoring floral diversity where propolis samples can be used to indicate plant species richness (biodiversity) and the presence of specific species relevant to conservation within their foraging area.
Explosive pollen release is documented in many plant families, including the Fabaceae. Desmodium setigerum E. Mey (Fabaceae) is a perennial herb with single trip explosive pollen release found in eastern Africa, and the unique ability to reverse floral colour change if insufficient pollination has occurred. However, little else is known about the pollination ecology of this species, what visitors can trigger explosive pollen release, and whether bee body size is related to pollination efficiency
. We investigated: 1) the breeding system of D. setigerum, and whether it is pollen limited; 2) whether flowers are visited early in the day allowing sufficient time for a second opportunity for pollination; and 3) what insect species visit D. setigerum and the relative efficacy of different flower visitors in relation to visitor size and pollination success. We found that although self-compatible, D. setigerum requires insect visitation to set seed as explosive pollen release is needed even for selfing. Most flowers are initially visited before 1400h, and by 1800h nearly all flowers have been tripped. Flowers were not pollen limited in this study, and were visited primarily by bees. We observed 16 visiting species, and there was a wide variation (0-404 grains) in the amount of pollen deposited on stigmas. Although almost all bees deposited some pollen, the mean number of pollen grains deposited in a single visit per species was negatively related to body size. However, one particular megachilid species deposited significantly more pollen grains than any other visitor and so is likely an important pollinator of this species. This provides insights into the pollination biology of this unique plant species, and adds to increasing literature on the relationships between bee body size, explosive pollen release and pollination effectiveness.
In this study we investigated whether the production of cleistogamous (CL) and chasmogamous (CH) floral morphs in Ruellia brevifolia is affected by water availability. To this end, the effects of two water levels were tested on plants grown in a greenhouse: soil at 100% water-holding capacity (WHC) (moist soil) and at 50% WHC (water scarcity). Additionally, we investigated fruit and seed production in plants at these two levels of water availability and evaluated whether the drought stress inter
feres with vegetative growth. The production of floral morphs depended on water availability: plants in moist soil produced only CH morphs and water-stressed plants produced only CL morphs. Fruit production was higher at the higher level of water availability (30.5 ± 28.20 fruits/plant at 100% WHC versus 9 ± 6.04 fruits/plant at 50% WHC; t = 4.384; P < 0.01). The mean number of seeds produced by CH and CL morphs were, respectively, 5.93 ± 2.24 and 8.17 ± 2.07 seeds/fruit (t = - 3.304; P < 0.01). Although CL morphs produced a greater number of seeds, the total seed production per plant was higher in plants at 100% WHC (180.86 seeds/plant in CH morphs versus 73.53 seeds/plant in CL morphs of plants in soil at 100% and 50% WHC, respectively; t = - 2.759; P < 0.01). The plants in soil at 100% WHC were taller (0.48 m ± 0.07) in relation to plants in soil at 50% WHC (0.24 m ± 0.04) (t = 1.781; P < 0.01). This study provides new information about the sexual reproductive strategy of R. brevifolia , indicating that the main factor inducing cleistogamy is drought stress.
Miller-Struttmann et al. (2015) suggest that, in a North American alpine ecosystem, reduced flower abundance due to climate change has driven the evolution of shorter tongues in two bumble bee species. We accept the evidence that tongue length has decreased, but are unconvinced by the adaptive explanation offered. It posits foraging responses and competitive relationships not seen in other studies and interprets phenotypic change as evidence of evolutionary adaptation. By oversimplifying a compl
ex phenomenon, it may exaggerate the potential for bees to quickly adapt to environmental changes.
We compared pollination and seed set of bicolor and concolor morphs in self-incompatible, Viola pedata over two seasons in two populations of unequal sizes. One population grew on a wooded slope (CR) and the second on an exposed glade (SNR). Both were burned in 2014. The number of flowers produced by concolor plants at SNR was higher in 2014 while the number of flowering bicolors increased at CR in 2015. Petal temperatures, regardless of site, showed that dark purple, posterior petals of b
icolors were consistently warmer than their own mauve-lilac, anterior (lip) petals and the all mauve petals of concolors. Major pollen vectors were female bees (Andrenidae, Apidae and Halictidae) but polylectic, Andrena carlinii dominated both sites. Bees foraged on flowers upside down or right side up but neither mode correlated with either morph. Bees foraged preferentially on concolor at both sites. Pistils containing pollen tubes were higher in concolor pistils at both sites with a marginally greater number of tubes penetrating concolor ovules regardless of site or year. While both populations produced more seeds in 2014 SNR plants always produced more seeds than CR plants. The increasing numbers of bicolor plants at CR in 2015 suggested that bicolors may equal or outnumber concolors when dark petals offer additional warmth to ectothermic pollinators in a shady (cooler) forest vs. an open, sunny glade. Subtle environmental factors may give a floral trait a selective advantage influencing fitness in an unbalanced polymorphism persisting in localized populations.
In a recent paper, we reported on the evolution of shorter tongues in two alpine bumble bee species in response to climate-induced flower deficits. De Keyzer et al. concede that tongue lengths have decreased but criticize the level of support for our claims. Here, we address the alternative mechanisms they proposed, highlight evidence presented in the supplementary material, and elaborate on the support for our claims in the literature. De Keyzer et al.’s criticisms reflect concerns about the
misrepresentation of our work in the popular press. To clarify, we do not imply that evolutionary rescue is necessarily a prudent conservation strategy; we illustrate that remote bumble bee populations buffered from other environmental stressors have undergone an adaptive evolutionary response to dwindling resources under climate change.
Up to 60% of the bee species of a region are oligolectic; they collect pollen only from a closely related group of plants though nectar-collecting choices are often broader. Bee specialists are expected to be superior to generalists in gathering pollen from their host plants and perhaps in transferring pollen to host stigmas. We used the oligolege Diadasia nitidifrons and its pollen-host Iliamna bakeri to ask if specialists 1) were more efficient than generalists as pollen-collectors; 2) deposit
ed more pollen on stigmas than generalists; and 3) if pollen-collectors removed and deposited more pollen than did nectar-collectors. We found support for the first and third hypotheses. Diadasia pollen- and nectar-collectors removed more pollen per flower-visit than did their primary generalist competitors ( Agapostemon spp.). The superior pollen-gathering efficiency of Diadasia exceeded differences that might be attributed to size: although Agapostemon females are, on average, 12.5% smaller than Diadasia females, pollen-collecting Agapostemon left 22.9% more pollen in flowers than did Diadasia . We found no difference between taxa in time spent foraging on a single flower. Diadasia and Agapostemon pollen-collectors deposited significantly more pollen on I. bakeri stigmas than did nectar-collectors; there was no difference between taxa in pollen deposition. Diadasia was superior to generalists as a pollinator in two ways: Diadasia was 1) a more reliable presence in I. bakeri populations; and 2) always most abundant at I. bakeri flowers. The association between D. nitidifrons and I. bakeri appears to be another example of a highly specialised bee affiliated with an unspecialised host-plant.
Recent advances in the study of pollination networks have improved our ability to describe species interactions at the community level. In this study, we compared the abundance and network strength of facultative and obligate nectar-feeding bats to determine their roles in pollinating mixed fruit orchards. We were particularly interested in the effect of distance from forests and caves on the foraging activity of these two bat groups. For this study, we examined 10 pairs of orchards; each pair c
onsisted of one orchard near to (< 1 km) and one orchard far from (> 7 km) the forest edge. We estimated the abundance of each bat group (nectarivorous vs. frugi-nectarivorous) using video observations to determine floral visitation rates. A pollination network was then created for each of the 20 study orchards and network strength was calculated for each bat group at each orchard. We found that nectarivorous bats showed higher abundance and network strength than frugi-nectarivorous bats. Both bat abundance and network strength were negatively correlated with distance to the nearest cave, however, only network strength was affected by distance to the forest. These results corroborate the importance of nectarivorous bats in pollinating crops within southern Thailand’s mixed fruit orchards. Higher network strength of bats near forests and caves emphasizes the role of natural habitats as pollinator sources.
Animal pollination is a vital ecological process in both natural and agricultural ecosystems. Economic valuation studies have demonstrated that pollination services may underpin a significant proportion of global crop market outputs. However these assessments are probably under-estimates because they have rarely included non-food crops, for which very few data are currently available. In particular, culturally symbolic plants have received no attention. Here we show that pollinators have conside
rable economic benefits to sales of European holly and mistletoe, two seasonal cultural crops that are almost wholly dependent upon insect pollinators for the production of ornamental berries. Analyses of a time series of auction records spanning 11 years indicates that wholesale prices paid for holly with berries are twice those paid for the crop without berries, whilst mistletoe with berries sells for almost three times the price of the crop lacking fruit. The benefits of this insect pollination ecosystem service to this market are therefore considerable. These findings demonstrate that pollinators can play a significant role in adding value to crops that provide resources other than food. In the future such crops should be included in assessments of regional and global value of animal pollination to increase the accuracy of assessments of the value of pollination as an ecosystem service. Our results also support arguments for continued efforts to conserve pollinator diversity and abundance in agro-ecological systems, not least for their contribution as providers of ecosystem services. NOTE: Supporting information to this article may be found in the left menu.
The study of foraging behaviour in plant-pollinator mutualisms has benefitted from the use of artificial flowers to manipulate floral display traits and the delivery of floral rewards. The two most common floral rewards are pollen and nectar; some pollinators, such as bees, are obliged to collect both for survival and reproduction. While flexible designs for artificial flowers providing nectar rewards abound, useful designs for artificial flowers that dispense pollen are few. This disparity mirr
ors a heavy emphasis on nectar collection in the study of pollinator foraging behaviour. In this study we describe a novel, easily constructed and modifiable artificial flower that dispenses flexible amounts of pollen via an ‘anther’ composed of a chenille stem. Using controlled lab assays, we show that more pulverized honeybee pollen is collected by bumblebee ( Bombus impatiens ) workers at chenille stem feeders than at dish-type feeders. We suggest that the paucity of studies examining pollinator cognition in the context of pollen rewards might be partly remedied if researchers had access to inexpensive and easily adjustable pollen-offering surrogate flowers. NOTE: Supporting information to this article may be found in the left menu.
Specialist oligoleges are bees with narrow dietary niche breadths often touted to have foraging specializations that enhance their pollination efficiency above that of co-foraging generalists (polyleges) such as honeybees Apis mellifera L. This study and many comparative pollinator efficacy studies in crops show that oligoleges on a per bee basis are not always the most efficient pollinators. Percentage of stigmatic contact visits by populations of oligolectic Ptilothrix bombiformis (Cresson) in
Maryland and Mississippi show that adult bees contact stigmas and transfer 70+ pollen grains during 2% - 3% of floral visits. As low as these percentages seem, pollination efficiency of this bee varies from negative values due to the removal of stigmatic pollen during some visits to increases of 30% as Hibiscus petals close and spikes of 300% - 1000% as Ptilothrix adults display aggression inside flowers. Aggressive P. bombiformis tussle with each other, often grappling with, lunging at, and biting conspecifics. Opponents will often lose their balance, tumble around inside flowers and, in the process, more efficiently pollinate host blooms . Such aggressive interactions constituted 5% of visitation bouts to Hibiscus flowers, yet accounted for ~20% of contact visits that transferred 10 or more pollen grains per stigma . Tussles therefore represent brief agonistic entanglements that can enhance the pollination efficiency of solitary bees at host plants with large herkogamous blooms. More complex behavioural interactions between different sexes and species of foraging bees may explain the importance of greater bee diversity to overall pollinator effectiveness.
Haskap ( Lonicera caerulea L.) is a temperate fruiting shrub grown commercially in northern regions of Europe, Asia, and North America. Haskap is self-incompatible and requires insect pollinators in order to set fruit; however, very little is currently known about its floral biology or pollinator specializations, particularly in North American cultivars. Here, we examine floral longevity, nectar dynamics, the timing of anther dehiscence, and stigma receptivity in flowers of greenhouse-grown ‘Tun
dra’, a Haskap cultivar developed and grown in Saskatchewan, Canada. Anthesis lasted 83.3 ± 25.9 hours (mean ± SD) in un-pollinated flowers; pollination caused early senescence within 34.3 ± 15.2 hours after pollination. Nectar was present from the onset of anthesis, and nectar volume peaked at 9-16 hours after opening. Nectar volume was maintained throughout anthesis and was not resorbed prior to abscission of the corolla from the ovary, and nectar removed during anthesis was replenished to the original volume. The stigma showed a reaction to hydrogen peroxide while still in the bud stage, suggesting it is receptive even before the flower opens. Early stigma receptivity, nectar production, and anther dehiscence maximize opportunities to be successfully pollinated, along with high floral longevity and pollination-triggered senescence. These results suggest that Haskap flowers utilize a generalist, rather than a specialized, pollination strategy. Observations that some flowers open in the evening or were already open in the morning suggest that nocturnal pollinators such as moths may be important, in addition to known diurnal pollinators.
Geographic variation in pollination ecology is poorly documented, if at all, in many plant-pollinator systems. Great insights could be gained into the abiotic and biotic factors which impact the evolution of floral properties and their potential to lead to speciation by doing so, as both can vary naturally over the geographic range of a plant species. We characterized the pollination ecology of the Andean tree Oreocallis grandiflora (Family: Proteaceae) at the northern and southern ends of its r
ange in Ecuador and Peru in terms of flower morphology, nectar properties, pollinators and plant reproduction. We found significant divergence in the two populations in terms of style length and flower openness, nectar standing crop and secretion rate, and pollinator community. We did not find a significant difference in the length of the pollen presenter or in nectar sucrose concentration by weight (% Brix). The observed divergence in floral traits between the two study populations may be related to a combination of factors, including genetic drift and isolation by distance, distinctive suites of pollinators, or heterospecific pollen competition, which future studies should further investigate. This study demonstrates that pollination ecology can vary substantially across the geographic range of a species, with implications for delimiting species and subspecific taxa. NOTE: Supporting information to this article may be found in the left menu.
Plants provision pollinators with a variety of nutritious or otherwise beneficial rewards. Hummingbirds (primarily Calypte anna ) pollinate the columbine Aquilegia eximia . In addition to drinking nectar, they glean entrapped insects from its sticky surfaces. To test the hypothesis that this insect carrion, an abundant and easily-collected protein source, serves as a provision to the pollinator and increases pollination I experimentally manipulated this reward and measured pollination success. I
set up three treatments - an insect carrion addition, carrion removal, and an unmanipulated control - on small patches of the plant in each of five populations of A. eximia . Pollination success, measured by seed set in emasculated flowers, was unaffected by carrion level. Pollination success positively correlated with average floral display in each patch; this suggests that local nectar reward in an area is more important than this proteinaceous reward in determining pollination success. Stickiness in this system may function as an effective exclusion mechanism for smaller-bodied pollinators. While this study did not demonstrate that captured insects increased reproductive success of this columbine, this interaction (and pollinator exclusion) may play a role in other hummingbird-plant interactions, as hummingbird pollination and insect-entrapment occur together in at least nine species of six plant families.
Research on diurnal plant–pollinator interactions indicates that a small number of generalist plants provide a disproportionately high amount of floral resources to pollinating insects. Identifying these generalist plants would help prairie restoration specialists select species that will provide forage for the majority of pollinator taxa. Field research in three Canadian fescue ( Festuca hallii ) prairie preserves that were at most 3.3 km away from each other was conducted in 2014 and 2015 to c
reate pooled, weighted, plant–insect visitor matrices for each site. Using these matrices, generalization (G) scores were calculated for each plant species to help assess their importance to wild insect visitors as this method controls for differences in insect abundances over the year. The three species with the highest average generalization scores were Solidago rigida , Erigeron glabellus and Symphyotrichum laeve . Species accumulation curves were created to determine how many plant species would need to be present before most pollinator taxa would have at least one acceptable forage species. This research indicates that the 16 plant species (33% of the total) with the highest average generalization scores were visited by 90% of the observed pollinator taxa. To detect exceptionally attractive plant species while accounting for natural differences in abundance, we calculated the insect, bee and fly visitation rates per inflorescence. There was several specialized plant species that were visited frequently by bees. Most of these specialized plants had purple or yellow, tubular flowers, and bloomed in mid to late summer when bee populations were most numerous. NOTE: Supplementary files to this article can be found in the left menu.
Bees provide important pollination services that maintain native plant populations and ecosystem resilience, which is critical to the conservation of the rich and endemic biodiversity of Kaya forests along the Kenyan Coast. This study examined bee composition and floral resources from the forest core to the surrounding farmlands around Kaya Muhaka forest. In total, 755 individual bees, representing 41 species from three families were recorded: Apidae, Halictidae and Megachilidae. Overall, Apidae
were the most abundant with a proportion of 76% of the total bee individuals, Halictidae at 14% and Megachilidae at 10%. Bee composition was similar between forest edge and crop fields as compared to forest core and fallow farmlands. We found a significant decrease in bee diversity with increasing distance from the forest to the surrounding farming area. A high abundance of bees was recorded in fallow farmland, which could be explained by the high abundance of floral resources in the habitat. We found floral resources richness to significantly affect bee species richness. These findings are important for understanding the effects of land use change on insect pollinators and their degree of resilience in disturbed habitats.
The pollen deposited during a single visit by a flower visitor (“single-visit deposition”; SVD) is often measured by removing the stigma from the flower and counting the pollen grains deposited under a microscope. This process precludes study of any subsequent interactions between the flower and later visitors (such as pollen removal from the stigma). Furthermore, if the stigma is excised too soon after the pollinator visit, the flower may be rendered infertile, such that any analyses of fruit o
r seed yield in relation to pollen deposition must be done indirectly. Here, a method of pollen deposition measurement was developed using macro photography and the open-source image-analysis software program ImageJ/Fiji. Using colour segmentation options within the program, the pollen grains can be distinguished from the background stigmatic surface, and the percentage of stigma coverage can be calculated. This pollen deposition measurement method leaves the sampled flower in the field to develop into fruit, allowing any subsequent yield or quality analyses to be conducted directly.
Across angiosperm species, the longevity of individual flowers can range from fixed to highly plastic. The orchid family is noteworthy for frequent reports of species in which flower lifespans are greatly prolonged if flowers are not pollinated. Less dramatic cases of pollination-induced senescence of anthesis have been reported for various species in other families, but such reports are scattered. Frequently, such findings are peripheral components of more general pollination studies. Because p
ollination-dependent plasticity can ameliorate phenological dislocations between plants and pollinators, it is worthwhile to conduct systematic surveys of its magnitude and taxonomic distribution. As a start, we report a set of experiments comparing the active lifespans of pollinated flowers to those of unpollinated controls in a set of nine species from a local subalpine flora. In all species, unpollinated flowers had longer mean times of receptiveness than pollinated ones, although the differences in means were often small. Three species exhibited significantly extended floral longevity in the absence of pollination.