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

AbstractAccurate predictions of pollination service delivery require a comprehensive understanding of the interactions between plants and flower visitors. To improve measurements of pollinator performance underlying such predictions, we surveyed visitation frequency, pollinator effectiveness (pollen deposition ability) and pollinator importance (the product of visitation frequency and effectiveness) of flower visitors in a diverse Mediterranean flower meadow. With these data we constructed the largest pollinator importance network to date and compared it with the corresponding visitation network to estimate the specialisation of the community with greater precision. Visitation frequencies at the community level were positively correlated with the amount of pollen deposited during individual visits, though rarely correlated at lower taxonomic resolution. Bees had the highest levels of pollinator effectiveness, with Apis, Andrena, Lasioglossum and Osmiini bees being the most effective visitors to a number of plant species. Bomblyiid flies were the most effective non-bee flower visitors. Predictions of community specialisation (H2′) were higher in the pollinator importance network than the visitation network, mirroring previous studies. Our results increase confidence in existing measures of pollinator redundancy at the community level using visitation data, while also providing detailed information on interaction quality at the plant species level.

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Types of Flower Visitors: Syndromes, Constancy, and Effectiveness

Pollination and Floral Ecology ◽

10.23943/princeton/9780691128610.003.0011 ◽

2011 ◽

Author(s):

Pat Willmer

Keyword(s):

Adaptive Radiation ◽

Convergent Evolution ◽

Pollination Syndromes ◽

Pollinator Effectiveness ◽

Flower Constancy ◽

Flower Visitors ◽

Floral Constancy ◽

Effective Pollinators

This chapter examines pollination syndromes, floral constancy, and pollinator effectiveness. Flowers show enormous adaptive radiation, but the same kind of flower reappears by convergent evolution in many different families. Thus many families produce rather similar, simple bowl-shaped flowers like buttercups; many produce similar zygomorphic tubular lipped flowers; and many produce fluffy flower heads of massed (often white) florets. These broad flower types are the basis of the idea of pollination syndromes—the flowers have converged on certain morphologies and reward patterns because they are exploiting the abilities and preferences of particular kinds of visitor. After providing an overview of pollination syndromes, the chapter explains why pollination syndromes can be defended. It then considers flower constancy, along with the distinction between flower visitors and effective pollinators. It concludes with some observations on how flower visitors can contribute to speciation of plants through specialization and through their constancy.

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Identifying the Real Pollinators? Exotic Honeybees Are the Dominant Flower Visitors and Only Effective Pollinators of Avicennia marina in Australian Temperate Mangroves

Estuaries and Coasts ◽

10.1007/s12237-013-9711-3 ◽

2013 ◽

Vol 37 (3) ◽

pp. 621-635 ◽

Cited By ~ 18

Author(s):

Tyge D. Hermansen ◽

David R. Britton ◽

David J. Ayre ◽

Todd E. Minchinton

Keyword(s):

Avicennia Marina ◽

Flower Visitors ◽

The Real ◽

Effective Pollinators

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Contrasting pollination efficiency and effectiveness among flower visitors of Malva sylvestris, Borago officinalis and Onobrychis viciifolia

Journal of Pollination Ecology ◽

10.26786/1920-7603(2017)421 ◽

2017 ◽

Vol 21 ◽

Author(s):

Anna Gorenflo ◽

Tim Diekötter ◽

Mark Van Kleunen ◽

Volkmar Wolters ◽

Frank Jauker

Keyword(s):

Plant Species ◽

Pollen Deposition ◽

Pollinator Effectiveness ◽

Borago Officinalis ◽

Flower Visitor ◽

Flower Visitors ◽

Onobrychis Viciifolia ◽

Single Visit ◽

Malva Sylvestris ◽

Visitation Frequency

Biotic pollination is an important factor for ecosystem functioning and provides a substantial ecosystem service to human food security. Not all flower visitors are pollinators, however, and pollinators differ in their pollination performances. In this study, we determined the efficiencies of flower visitors to the plant species Malva sylvestris, Borago officinalis and Onobrychis viciifolia by analysing stigmatic pollen deposition. We further calculated pollinator effectiveness by scaling up single-visit pollen deposition using visitation frequency. Flower-visitor groups differed in their efficiencies at the single-visit level and not all of them deposited more pollen compared to unvisited stigmas. Bumblebees tended to be most efficient in depositing pollen per single visit across the three plant species. Due to the by far highest visitation frequencies, Apis mellifera showed the highest effectiveness in depositing pollen per hour for M. sylvestris and B. officinalis, but not for O. viciifolia, for which the Bombus lapidarius complex was both the most frequent and the most effective pollinator group. Hence, the most frequent flower visitors were most effective in our study. For non-dominant pollinator groups, however, visitation frequencies contributed disproportionally to pollinator effectiveness. Thus, combining pollen deposition per single-visit with visitation frequency is necessary to reveal true pollinator performance and to better understand flower-visitor interactions.

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Pollination in the Rainforest: Scarce Visitors and Low Effective Pollinators Limit the Fruiting Success of Tropical Orchids

Insects ◽

10.3390/insects12100856 ◽

2021 ◽

Vol 12 (10) ◽

pp. 856

Author(s):

Hortensia Cabrera Reyes ◽

David Draper ◽

Isabel Marques

Keyword(s):

Fruit Set ◽

Seed Viability ◽

Climatic Conditions ◽

Single Plant ◽

Flower Visitors ◽

Pollination Success ◽

Pollination Limitation ◽

Orchid Pollination ◽

Low Levels ◽

Effective Pollinators

A single plant might be visited by many flower visitors but not all might act as pollinators. Legitimate pollinators might also differ considerably in their efficiency, limiting pollination success. Unsuitable climatic conditions such as rain also affect pollinator activity. However, in the evergreen rainforest there is no prolonged dry season and flowering occurs usually under rain. Here, we explore the dependence on pollinators and the efficiency of flower visitors for the fruiting success of 10 Andean rainforest orchids. All species were self-compatible but strictly pollinator-dependent. Overall, we found low levels of fruit set in control flowers while experimental geitonogamous and cross-pollinations increased fruit set, revealing extensive pollination limitation in all populations. Seed viability dropped considerably after self and geitonogamous pollinations suggesting the possibility of early-acting inbreeding depression. Even though we monitored flower visitors on an extensive survey, few visitors were seen in these species and even fewer acted as legitimate pollinators. Thus, even though orchid pollination might be extremely diversified, these results show that few visitors are pollinating these species, explaining the low levels of fruit set recorded in the area studied.

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Cheaters in mutualism networks

Biology Letters ◽

10.1098/rsbl.2009.1021 ◽

2010 ◽

Vol 6 (4) ◽

pp. 494-497 ◽

Cited By ~ 44

Author(s):

Julieta Genini ◽

L. Patrícia C. Morellato ◽

Paulo R. Guimarães ◽

Jens M. Olesen

Keyword(s):

Network Topology ◽

Strong Impact ◽

Network Organization ◽

Flower Visitors ◽

Interacting Species ◽

Flower Visitation ◽

Different Types ◽

Network Studies ◽

Effective Pollinators

Mutualism-network studies assume that all interacting species are mutualistic partners and consider that all links are of one kind. However, the influence of different types of links, such as cheating links, on network organization remains unexplored. We studied two flower-visitation networks (Malpighiaceae and Bignoniaceae and their flower visitors), and divide the types of link into cheaters (i.e. robbers and thieves of flower rewards) and effective pollinators. We investigated if there were topological differences among networks with and without cheaters, especially with respect to nestedness and modularity. The Malpighiaceae network was nested, but not modular, and it was dominated by pollinators and had much fewer cheater species than Bignoniaceae network (28% versus 75%). The Bignoniaceae network was mainly a plant–cheater network, being modular because of the presence of pollen robbers and showing no nestedness. In the Malpighiaceae network, removal of cheaters had no major consequences for topology. In contrast, removal of cheaters broke down the modularity of the Bignoniaceae network. As cheaters are ubiquitous in all mutualisms, the results presented here show that they have a strong impact upon network topology.

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Empidine dance flies pollinate the woodland geranium as effectively as bees

Biology Letters ◽

10.1098/rsbl.2019.0230 ◽

2019 ◽

Vol 15 (7) ◽

pp. 20190230 ◽

Cited By ~ 1

Author(s):

Vincent Lefebvre ◽

Christophe Daugeron ◽

Claire Villemant ◽

Colin Fontaine

Keyword(s):

Seed Set ◽

Flower Visitors ◽

Single Visit ◽

Subalpine Meadow ◽

Pollination Effectiveness ◽

Flower Visiting ◽

Plant Pollinator ◽

Effective Pollinators ◽

Dance Fly ◽

High Diversity

Most flowering plants species rely on insects for pollination, a successful mutualism allowing them to reproduce over wide areas while flower-visitors are rewarded with food. This association is so conspicuous in the case of bees that other groups of potential pollinators, especially flies, have long been underestimated. However, visitors are not always pollinators. While the importance of flies in plant–visitor networks is now acknowledged, their pollination effectiveness has hardly been investigated. In this study, we assessed the pollination effectiveness of Geranium sylvaticum flower-visitors using single-visit seed set experiments, in a subalpine meadow where flies are predominant. We found that: (i) empidine dance flies were the most frequent visitors of G. sylvaticum ; (ii) a single-visit by an empidine dance fly produced the same average number of seeds as a visit by a bee; (iii) large pollinators were more efficient than small pollinators irrespective of their identity. As a conclusion, large empidines were the main pollinators of G. sylvaticum . Considering the high diversity and abundance of flower-visiting fly species, such results showing their ability to be as effective pollinators as bees should encourage further studies to develop a better understanding on their role in plant–pollinator networks.

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Cucurbits as a model system for crop pollination management

Journal of Pollination Ecology ◽

10.26786/1920-7603(2019)535 ◽

2019 ◽

Vol 25 ◽

Author(s):

Jessica Louise Knapp ◽

Juliet Laura Osborne

Keyword(s):

Bombus Terrestris ◽

Species Conservation ◽

Floral Resources ◽

Pollen Deposition ◽

Pollination Services ◽

Pollinator Visitation ◽

Crop Species ◽

Pollinator Behaviour ◽

Wild Bee ◽

Effective Pollinators

Cucurbit crops have steadily increased in production over the last 50 years, particularly in Asia where pioneering technological advancements and genetic improvements have created new hybrid varieties. Generally, cucurbits are dependent on insect-pollination for fruit set and are popular species for pollination studies. This review systematically summarises pollination research conducted in the major food genera of cucurbits: Cucurbita, Cucumis, and Citrullus, to ask: 1) what are cucurbits’ requirement for pollination and their most effective pollinators? And 2) Does pollinator management increase pollinator visitation to, and yield of, cucurbit crops? These accounts of cucurbit pollination demonstrate that wild bee species such as Bombus terrestris, B. impatiens and Eucera spp. were frequently able to fulfil the pollination requirements of multiple cucurbit species. However, pollinator behaviour, pollen deposition on stigmas, and pollinators’ contribution to yield vary between cucurbit species and study site. Nonetheless, the provision of additional floral resources at both field and farm scales may help to encourage pollination of cucurbit species whilst supporting pollinators’ nutritional requirements beyond those already provided by the cucurbit crop. Synthesising studies on cucurbits’ requirement for pollination and how pollinators vary spatially and temporally in the landscape can extend beyond cucurbit systems to inform growers and pollination ecologists of other pollinator-dependent crop species wishing to maximise pollination services, species conservation; or both.

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Linking modern pollen accumulation rates to biomass: Quantitative vegetation reconstruction in the western Klamath Mountains, NW California, USA

The Holocene ◽

10.1177/0959683620988038 ◽

2021 ◽

pp. 095968362098803

Author(s):

Clarke A Knight ◽

Mark Baskaran ◽

M Jane Bunting ◽

Marie Champagne ◽

Matthew D Potts ◽

...

Keyword(s):

Mean Squared Error ◽

Plant Biomass ◽

Source Area ◽

Pollen Deposition ◽

Accumulation Rates ◽

Klamath Mountains ◽

Plant Abundance ◽

Circular Area ◽

Value Analysis ◽

Pollen Accumulation Rates

Quantitative reconstructions of vegetation abundance from sediment-derived pollen systems provide unique insights into past ecological conditions. Recently, the use of pollen accumulation rates (PAR, grains cm−2 year−1) has shown promise as a bioproxy for plant abundance. However, successfully reconstructing region-specific vegetation dynamics using PAR requires that accurate assessments of pollen deposition processes be quantitatively linked to spatially-explicit measures of plant abundance. Our study addressed these methodological challenges. Modern PAR and vegetation data were obtained from seven lakes in the western Klamath Mountains, California. To determine how to best calibrate our PAR-biomass model, we first calculated the spatial area of vegetation where vegetation composition and patterning is recorded by changes in the pollen signal using two metrics. These metrics were an assemblage-level relevant source area of pollen (aRSAP) derived from extended R-value analysis ( sensu Sugita, 1993) and a taxon-specific relevant source area of pollen (tRSAP) derived from PAR regression ( sensu Jackson, 1990). To the best of our knowledge, aRSAP and tRSAP have not been directly compared. We found that the tRSAP estimated a smaller area for some taxa (e.g. a circular area with a 225 m radius for Pinus) than the aRSAP (a circular area with a 625 m radius). We fit linear models to relate PAR values from modern lake sediments with empirical, distance-weighted estimates of aboveground live biomass (AGLdw) for both the aRSAP and tRSAP distances. In both cases, we found that the PARs of major tree taxa – Pseudotsuga, Pinus, Notholithocarpus, and TCT (Taxodiaceae, Cupressaceae, and Taxaceae families) – were statistically significant and reasonably precise estimators of contemporary AGLdw. However, predictions weighted by the distance defined by aRSAP tended to be more precise. The relative root-mean squared error for the aRSAP biomass estimates was 9% compared to 12% for tRSAP. Our results demonstrate that calibrated PAR-biomass relationships provide a robust method to infer changes in past plant biomass.

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Landscape Enhancements in Apple Orchards: Higher Bumble Bee Queen Species Richness, but No Effect on Apple Quality

Insects ◽

10.3390/insects12050421 ◽

2021 ◽

Vol 12 (5) ◽

pp. 421

Author(s):

Amélie Gervais ◽

Marc Bélisle ◽

Marc J. Mazerolle ◽

Valérie Fournier

Keyword(s):

Species Richness ◽

Bumble Bees ◽

Bumble Bee ◽

Pesticide Use ◽

Apple Orchards ◽

Seed Number ◽

Apple Production ◽

Apple Quality ◽

Effective Pollinators ◽

Quality Weight

Bumble bees are among the most effective pollinators in orchards during the blooming period, yet they are often threatened by the high levels of pesticide use in apple production. This study aimed to evaluate the influence of landscape enhancements (e.g., hedgerows, flower strips) on bumble bee queens in apple orchards. Bumble bee queens from 12 orchards in southern Québec (Canada) were marked, released, and recaptured in the springs and falls of 2017 to 2019. Half of the 12 orchards had landscape enhancements. Apples were harvested in 2018 and 2019 to compare their quality (weight, diameter, sugar level, and seed number) in sites with and without landscape enhancements. Species richness, as well as the occurrence of three species out of eight, was higher in orchards with landscape enhancements than in orchards without such structures. The occurrence of Bombus ternarius was lower in orchards with high levels of pesticide use. Apples had fewer seeds when collected in orchards with landscape enhancements and were heavier in orchards that used more pesticides. Our work provides additional evidence that landscape enhancements improve bumble bee presence in apple orchards and should therefore be considered as a means to enhance pollination within farms.

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