Insect-mediated Pollination Research Articles

Strategic honey bee hive placement improves honey bee visitation but not pollination in northern highbush blueberry.

Commercial blueberry Vaccinium spp. (Ericales: Ericaceae) production relies on insect-mediated pollination. Pollination is mostly provided by rented honey bees, Apis mellifera L. (Hymenoptera: Apidae), but blueberry crop yields can be limited due to pollination deficits. Various hive placement strategies have been recommended to mitigate pollination shortfalls, but the effect of hive placement has received limited formal investigation. This study explores the effects of clumped and dispersed hive placement strategies on honey bee visitation and pollination outcomes in "Bluecrop" and "Duke" fields over 2 years (2021 and 2022) within 2 economically important regions of production in the United States-the Midwest (Michigan) and Pacific Northwest (Oregon and Washington). Clumping hives consistently increased honey bee visitation rate but did not result in higher fruit set, fruit weight, or seed count. Increases in honey bee visitation through clumping could perhaps improve pollination outcomes in more pollination-limited blueberry cultivars and other pollination-dependent crops. Clumping hives is substantially more efficient and cost-effective for beekeepers due to fewer drop locations and could lead to cost savings for both beekeepers and blueberry growers without growers sacrificing pollination levels and crop yields.

Ecological perspectives on female and male reproductive success with competition in two Serapias species.

The deceptive strategies by which orchids are pollinated and how these are capable of attracting pollinators remain understudied with regard to their implications for plant fitness. Despite their ecological importance, limited investigations have been conducted on sexual deception and shelter mimicry in orchid species, making this a compelling avenue in orchid biology research. To expand the knowledge of these reproductive mechanisms, we studied the pollination of Serapias lingua and S. parviflora in co-occurring and isolated sites in the Balearic Islands (Spain), further accentuated by the presence of a hybrid, indicating shared pollinators. We employed bagging and hand pollination experiments to examine the reproductive biology of the two species. Furthermore, we evaluated the influence of phenotypical and ecological factors on reproductive success, including biometric measurements, reproductive performance and neighbourhood diversity (co-flowering and pollinator communities). Reproductive mechanisms between these two orchid species exhibit substantial disparities. Serapias lingua relies primarily on insect-mediated pollination, while S. parviflora demonstrates self-reproduction capacity. Although events of open pollination are rare, hybridization occurs predominantly when S. lingua is the pollen donor. Fruit set in S. parviflora was positively correlated with plant height, while in S. lingua it was negatively associated with flower size. The coexistence of the two species positively affected pollinium removal in S. parviflora, but did not exert an influence on reproductive traits in S. lingua. Overall, biometric parameters were diminished in isolated compared with co-occurring sites. At the community level, the increased diversity of co-flowering species in the vicinity exhibited an inhibitory effect on pollinium removal in S. parviflora. Under a context of pollinator loss or phenological mismatch between pollinator presence and flowering, the selfing capacity of S. parviflora would guarantee reproduction whereas S. lingua survival would be compromised. Furthers studies are needed to assess the effects of phenotypical and ecological factors on reproductive success of S. lingua in pollinator-decline scenarios.

Pollination deficits and their relation with insect pollinator visitation are cultivar-dependent in an entomophilous crop

Insects contribute considerably to global crop pollination, with pollination deficits being documented for multiple entomophilous or pollinator-dependent crops. Different cultivars of crops are being cultivated within and across production regions, so it is essential to understand the cultivar variability of pollination deficits. Here, we used a dataset from 286 sites from multiple production regions to develop a synthesis on pollination deficits in two widely cultivated highbush blueberry cultivars, ‘Bluecrop’ and ‘Duke’. Additionally, we determined if bee visitation or bee richness reduces pollination deficits in these cultivars. On average, neither cultivar showed pollination deficits regarding fruit set. However, for ‘Bluecrop’ we found pollination deficits for berry weight and seed set, which was not the case for ‘Duke’. Increasing total bee visitation reduced pollination deficits of both berry weight and seed set for ‘Bluecrop’. More specifically, a non-linear, negative exponential model best predicted this relation between bee visitation and pollination deficits. Our results highlight that pollination deficits and responses to pollinator visitation are variable between different cultivars of a single crop, which suggests opportunities to use certain cultivars that are less dependent on insect-mediated pollination in landscapes and regions where pollination services have been compromised. In addition, the non-linear response between bee visitation and pollination deficits suggests that optimal bee visitation rates need to be determined to improve pollination management and crop yield and to support accurate economic valuations of pollination services.

Insect-Mediated Pollination of Strawberries in an Urban Environment.

Pollination services provided by a diversity of pollinators are critical in agriculture because they enhance the yield of many crops. However, few studies have assessed pollination services in urban agricultural systems. We performed flower-visitor observations and pollination experiments on strawberries (Fragaria × ananassa) in an urban area near Paris, France, in order to assess the effects of (i) insect-mediated pollination service and (ii) potential pollination deficit on fruit set, seed set, and fruit quality (size, weight, and malformation). Flower-visitor observations revealed that the pollinator community solely comprised unmanaged pollinators, despite the presence of beehives in the surrounding landscape. Based on the pollination experiments, we found that the pollination service mediated by wild insects improved the fruit size as a qualitative value of production, but not the fruit set. We also found no evidence of pollination deficit in our urban environment. These results suggest that the local community of wild urban pollinators is able to support strawberry crop production and thus plays an important role in providing high-quality, local, and sustainable crops in urban areas.

High cross-pollination rate of Greek oregano (O. vulgare ssp. hirtum) with Common oregano (O. vulgare ssp. vulgare) under open field conditions as revealed by microsatellite marker analysis

We studied the mode of pollination in Greek oregano (Origanum vulgare ssp. hirtum) under both controlled and open pollination conditions. When grown indoors without the presence of insects, Greek oregano plants did not develop any seeds, indicating a low level of spontaneous self-pollination. Applying manual self-pollination under the same conditions resulted in only 16 seeds, of which only five were able to germinate. At the same time, a clonally propagated Greek oregano plant of the same genotype produced a rich set of over 300 seeds in open field conditions when the flowers were visited by insects in an area where no other Origanum species were observed. Analysis with SSR markers showed that over 70% of the seeds likely resulted from self-pollination, indicating that insect-mediated pollination is essential for the seed development. We further analyzed the cross-pollination of Greek oregano with Common oregano (O. vulgare ssp. vulgare) in open field conditions where the two subspecies were grown in close proximity. Applying SSR markers, we analyzed 83 plants obtained from seeds of three vegetatively propagated Greek oregano mother plants. Surprisingly, the results showed that all analyzed seedlings resulted from cross-pollination of Greek oregano with Common oregano, indicating that cross-pollination between the two subspecies can completely take over the self-pollination or cross-pollination between the Greek oregano plants. The possible impact of the observed high cross-pollination rate on the genetic origin of seeds of selected Greek oregano lines and varieties, as well as on the genetic diversity and structure of natural populations, is discussed.

The Pragmatist’s Guide to ESG

Click to increase image sizeClick to decrease image size Additional informationNotes on contributorsTodd CortTodd Cort is currently a senior lecturer in sustainability at the Yale School of Management with courtesy appointment at the Yale School of the Environment. He serves as faculty co-director for the Yale Center for Business and the Environment (CBEY) and the Yale Initiative on Sustainable Finance (YISF).Notes1 D. C. Esty and T. Cort, eds., Values at Work: Sustainable Investing and ESG Reporting (Springer Nature, 2020).2 T. Whelan, U. Atz, T. Van Holt, and C. Clark, Uncovering the Relationship by Aggregating Evidence from 1,000 Plus Studies Published between 2015–2020 (2021), https://www.stern.nyu.edu/sites/default/files/assets/documents/ESG%20Paper%20Aug%202021.pdf.3 Bloomberg Research, https://sponsored.bloomberg.com/article/mubadala/the-future-of-esg-Investing.4 D. Gelles, “How Environmentally Conscious Investing Became a Target of Conservatives,” New York Times, 28 February 2023, updated March 1, https://www.nytimes.com/2023/02/28/climate/esg-climate-backlash.html; J. Sommer, “On Wall St., ‘Socially Responsible’ Is Common Sense. In Congress, It’s Political,” New York Times, 4 March 2023, https://www.nytimes.com/2023/03/04/business/esg-socially-responsible-investing.html.5 G. Baker, “The Rising Backlash Against ESG Investing,” Wall Street Journal Opinion, 8 March 2023, https://www.wsj.com/podcasts/opinion-free-expression/the-rising-backlash-against-esg-investing/633ad782-974f-495b-955d-a7c62a0fd8a3.6 J. Ullrich and F. Powell, “What Is an ESG Score for Investing?,” USA Today, 1 March 2023, https://www.usatoday.com/money/blueprint/investing/what-is-esg-investing.7 L. Qiu, “No, Wokeness Did Not Cause Silicon Valley Bank’s Collapse,” New York Times, 15. March 2023, https://www.nytimes.com/2023/03/15/us/politics/silicon-valley-bank-collapse-woke-fact-check.html.8 See, for example, N. L. Erhardt, J. D. Werbel, and C. B. Shrader, “Board of Director Diversity and Firm Financial Performance,” Corporate Governance: An International Review 11, no. 2 (2003), 102–11; R. Lorenzo and M. Reeves, “How and Where Diversity Drives Financial Performance,” Harvard Business Review 30, January (2018): 1–5.9 PCBB, “Financial Institutions of All Sizes Increase DEI Efforts,” 4 August 2021, https://www.pcbb.com/bid/2021-08-04-financial-institutions-of-all-sizes-increase-dei-efforts.10 Net Zero Tracker, https://zerotracker.net (accessed 31 March 2023). Net zero commitments refer to a target of completely negating the amount of greenhouse gases produced by the companies activities through a combination of reduced emissions and sequestration of carbon from the atmosphere.11 IEA, Multiple Benefits of Energy Efficiency, IEA, Paris, 2019, https://www.iea.org/reports/multiple-benefits-of-energy-efficiency/emissions-savings, license: CC BY 4.0.12 U. Chrobak, “Solar Power Got Cheap. So Why Aren’t We Using It More?,” Popular Science, 8 October 2021, https://www.popsci.com/story/environment/cheap-renewable-energy-vs-fossil-fuels.13 For more information about the B-Corp Certification process and the organizing body B-Lab, see https://www.bcorporation.net/en-us/certification.14 The B-Lab provides a good summary of the purpose and specific legal protections offered under a benefit corporation registration: https://usca.bcorporation.net/benefit-corporation.15 “Impact investing” refers to investments made with the intention to generate positive, measurable social and environmental impact alongside a financial return (https://www.investopedia.com/terms/i/impact-investing.asp). “Blended finance” is the strategic use of development finance (concessional capital) for the mobilization of additional finance toward sustainable development in developing countries (https://www.oecd.org/dac/financing-sustainable-development/blended-finance-principles). “Negative screening” is the process of finding and then removing companies that score poorly on environmental, social, and governance (ESG) factors relative to their peers from an investment portfolio (https://corpgov.law.harvard.edu/2022/08/08/does-esg-negative-screening-work).16 https://www.the-future-of-commerce.com/2022/10/25/greenwashing-definition-stats.17 U.S. pollination value is estimated by A. Jordan, H. M. Patch, C. M. Grozinger, and V. Khanna, “Economic Dependence and Vulnerability of United States Agricultural Sector on Insect-Mediated Pollination Service,” Environmental Science & Technology (2021), doi:10.1021/acs.est.0c04786. The value of commercial pollination services globally is reported by https://www.knowledge-sourcing.com/report/global-pollination-market.18 R. Kerber and N. Z. Hussain, “Vanguard Quits Net Zero Climate Effort Citing Need for Independence,” Reuters, 7 December 2022, https://www.reuters.com/business/sustainable-business/vanguard-quits-net-zero-climate-alliance-2022-12-07.19 Vanguard, “An Update on Vanguard’s Engagement with the Net Zero Asset Managers Initiative (NZAM),” 7 December 2021, https://corporate.vanguard.com/content/corporatesite/us/en/corp/articles/update-on-nzam-engagement.html.20 https://www.blackrock.com/corporate/investor-relations/larry-fink-annual-chairmans-letter.21 A. Frericks, “While He’s Re-Writing the Music, Larry Fink Won’t Change the Underlying ESG Tune,” RealClear Markets, 24 March 2023, https://www.realclearmarkets.com/articles/2023/03/24/while_hes_re-writing_the_music_larry_fink_wont_change_the_underlying_esg_tune_889211.html.22 See, for example, https://www.morningstar.co.uk/uk/news/213385/will-the-sfdr-prevent-greenwashing.aspx.23 For more information on SASB, see https://www.sasb.org.24 There are hundreds of standards on ESG and sustainability today. Some of the more common types are (1) standards for management practices and performance, such as the ISO 14001 standard for environmental management systems; (2) auditing standards for nonfinancial accounting data, such as the ISAE 3000 Auditing Standard; (3) standards for producing voluntary ESG reports, such as the Global Reporting Initiative and the Sustainability Accounting Standards Board; (4) supply chain ESG performance and management system standards, such as the SA8000 Standard for Labor Rights or the Fairtrade Standards; and (5) product performance standards, such as Energystar ratings for energy efficiency.25 A. H. McGowan, “Life in the Anthropocene,” Environment: Science and Policy for Sustainable Development 65, no. 2 (2023): 6–14, doi:10.1080/00139157.2023.2167456.

Pollen and floral morphology of Androsace brevis (Hegetschw.) Ces. (Primulaceae), a vulnerable narrow endemic plant of the Southern European Alps

Androsace brevis (Hegetschw.) Ces. (Primulaceae) is a narrow endemic plant of the Southern Central European Alps that lives only above 2000 m asl and flowers immediately after snowmelt for a very short period during which the plant must guarantee successful sexual reproduction. Despite the vulnerability of this species, mainly due to increasing temperature, competition with plant communities shifting to higher altitudes, and possible mismatches with pollinators, nothing is known about its pollen and floral morphology. In this study we aim to provide a detailed description of these traits and to investigate how they might be related to possible pollination strategies and vectors. Pollen and flower samples were collected from the Lepontine and Orobic Alps (Northern Italy) populations. The pollen grains are small (polar axis: 19.17 µm ± 0.09; equatorial axis: 10.84 µm ± 0.1) with a prolate shape. The morphology of the flower, with the location of both stamens and pistil inside the corolla tube, and the coloured corolla mouths, ranging from yellow to purple, suggest that A. brevis requires insect-mediated pollination. Moreover, floral morphology does not show a particular insect-selective pattern in that the presence of both stamens and pistil less than 1 mm below the corolla mouth (Ø: 0.76 mm ± 0.05) might allow many high-altitude flower-visiting insects to reach both nectar and pollen. A generalist pollination strategy could be fundamental in contests characterized by harsh environmental conditions as it could counteract potential plant-pollinator mismatches due to increase in temperatures.

Bee visitation, pollination service, and crop yield in commodity and hybrid seed canola

Insect-mediated pollination of crops is an important service to agriculture, as increased insect visitation can increase fruit production by increasing pollen deposition. Unfortunately, pollination is often treated as a “black box”, and pollination management suffers from key knowledge gaps that hinder its greater utility, particularly the specific mechanisms underlying the processes of visitation, pollination, and fruit production. We present a causal model that links insect visitation to pollination to three separate components of yield, using field data from two types of canola (Brassica napus) production systems. Our results demonstrate that yield in commodity canola fields is primarily determined by plant size, and we found no relationship between honey bee (Apis mellifera) visitation and pollen deposition, or pollen deposition and seed yield. In contrast, yield in hybrid seed canola fields was similarly controlled by plant size, but there was also a strong relationship between alfalfa leafcutting bee (Megachile rotundata) visitation and pollen deposition, as well as pollen deposition and seed yield, meaning that leafcutting bee visitation in increased pollen deposition in seed canola fields, while honey bee visitation did not. This model serves as a step towards a dynamic model of pollination services, and highlights the relative importance of bee pollination in canola production.

Swallowtail butterflies and hawkmoths contribute equally to the pollination of Habenaria dentata (Orchidaceae)

Mixed pollination system with both diurnal and nocturnal visitors contributing to pollen transfer and seed set have been documented in many angiosperm species. The flowers of Habenaria species are usually green or white, with a long nectar secreting spur, and are usually interpreted as specialized for pollination by nocturnal moths. With a few exceptions, nocturnal moths and diurnal butterflies are both reported as pollinators of Habenaria species. However, the relative contributions made by moths versus butterflies to the reproductive success in the same orchid species has rarely been studied. We investigated the floral morphology, pollinators, pollination efficiency, and breeding system of Habenaria dentata in southern China. We showed that two species of diurnal swallowtail butterflies (Papilio helenus and Papilio memnon) and a species of crepuscular hawkmoth (Eupanacra mydon) were this orchid's effective pollinators. The pollinaria were attached to the eyes of these three insect species. Pollinator exclusion experiments showed that pollinarium removal and pollinium deposition rates on stigmas by butterflies (47.51% and 38.64%, respectively) were not significantly different from those made by hawkmoths (50.70% and 34.47%, respectively), indicating that diurnal and crepuscular visits contributed equally to reproductive success. As natural rates of insect-mediated pollination of our population of H. dentata resulted in fruit set rates of 93.33%, rejected the prospect that this population was pollinator limited. Hand pollination experiments indicated that H. dentata was self-compatible but without autonomous self-pollination. The proportion of well-developed seeds with large embryos in self-pollinated fruits was significantly lower than in cross-pollinated fruits, suggesting natural selection favors xenogamy. Our results highlighted the importance of both butterflies and hawkmoths contributing to the reproductive success of a rare orchid with a mixed pollination system.

Progresses of the international community to understand sunflower–pollinator interactions through multiscale approaches

The first web conference on sunflower–pollinator interactions gathered the international community around a major topic for sunflower productivity and ecosystemic biodiversity. Insect-mediated pollination is important for increasing sunflower seed yield, but is dependent on environmental factors. Climate change can impact sunflower-pollinator interactions by influencing both plant and pollinator behavior. Natural or artificially elevated ambient temperatures appear to accelerate floret development and advance the timing of pollen presentation to coincide with pollinator activities. Drought showed no major effect on morphological traits such anther or corolla length, but dramatically reduced nectar and pollen productions. Flavonol-glycoside conjugates lower head transpiration thereby mitigating deleterious effects of abiotic stresses. Wild pollinators show fine scale preferences among sunflower varieties, likely due to the different resource focus of wild and managed honeybees. Agricultural practices such as planting flower strips to provide nesting sites for wild pollinators, or supplementing crop plots with hives, can have a positive effect on insect-mediated pollination efficiency and ensure optimal yields. All together, recent results on sunflower–pollinator interactions pave the way to develop varieties and corresponding cropping systems more favorable to pollinator biodiversity while maintaining high yields in the context of climate change.

Toward evidence-based decision support systems to optimize pollination and yields in highbush blueberry

Highbush blueberry (Vaccinium spp.) is a globally important fruit crop that depends on insect-mediated pollination to produce quality fruit and commercially viable yields. Pollination success in blueberry is complex and impacted by multiple interacting factors including flower density, bee diversity and abundance, and weather conditions. Other factors, including floral traits, bee traits, and economics also contribute to pollination success at the farm level but are less well understood. As blueberry production continues to expand globally, decision-aid technologies are needed to optimize and enhance the sustainability of pollination strategies. The objective of this review is to highlight our current knowledge about blueberry pollination, where current research efforts are focused, and where future research should be directed to successfully implement a comprehensive blueberry pollination decision-making framework for modern production systems. Important knowledge gaps remain, including how to integrate wild and managed pollinators to optimize pollination, and how to provide predictable and stable crop pollination across variable environmental conditions. In addition, continued advances in pesticide stewardship are required to optimize pollinator health and crop outcomes. Integration of on- and off-farm data, statistical models, and software tools could distill complex scientific information into decision-aid systems that support sustainable, evidence-based pollination decisions at the farm level. Utility of these tools will require multi-disciplinary research and strategic deployment through effective extension and information-sharing networks of growers, beekeepers, and extension/crop advisors.

Quantifying the Influence of Pollen Aging on the Adhesive Properties of Hypochaeris radicata Pollen.

Simple SummaryPollination is the transfer of pollen from a plant’s male part (anther) to the corresponding female part (stigma). It is a fundamental biological process that ensures plant reproduction. Most studies investigate pollination from a biological perspective, but the underlying physical processes are poorly understood. Many plants rely on insects to transport pollen and the forces with which pollen adhere to insects and floral surfaces are fundamental for successful pollination. We quantified pollen adhesion by measuring the forces necessary to detach Hypochaeris radicata (catsear, a common insect-pollinated plant) pollen from glass and studied for the first time how the adhesion forces change with pollen aging. Our results show that newly formed adhesion bonds between H. radicata pollen and glass are stronger for fresh pollen than for old ones. On the other hand, when H. radicata pollen age in contact with glass, the adhesion between pollen and glass strengthens over time. These effects are probably caused by the viscous liquid covering most pollen (pollenkitt) changing its viscoelastic properties as it dries.Although pollination is one of the most crucial biological processes that ensures plant reproduction, its mechanisms are poorly understood. Especially in insect-mediated pollination, a pollen undergoes several attachment and detachment cycles when being transferred from anther to insect and from insect to stigma. The influence of the properties of pollen, insect and floral surfaces on the adhesion forces that mediate pollen transfer have been poorly studied. Here, we investigate the adhesive properties of Hypochaeris radicata pollen and their dependence on pollen aging by quantifying the pull-off forces from glass slides using centrifugation and atomic force microscopy. We found that the properties of the pollenkitt—the viscous, lipid liquid on the surface of most pollen grains—influences the forces necessary to detach a pollen from hydrophilic surfaces. Our results show that aged H. radicata pollen form weaker adhesions to hydrophilic glass than fresh ones. On the other hand, when a pollen grain ages in contact with glass, the adhesion between the two surfaces increases over time. This study shows for the first time the pollen aging effect on the pollination mechanism.

Diversity, abundance and foraging behaviour of insect pollinators in Radish (Raphanus raphanistrum subsp. sativus L.)

Some of the insect pollinators observed during the experimentation period [Apis dorsata (a) Apis florea (b) Apis cerana (c) Tetragonula iridipennis (d) Lassioglossum sp. (e) Delta conoideum (f) and Danaus chrysippus (g)] • Radish is crosspollinated due to sporophytic system of self-incompatibility. • Fifteen insect species, belonging to three orders were found to visit radish. • Species varied in foraging behaviour: visitation frequency and visitation rate. • Nectar robbing of Apis florea reduced their pollination efficiency. • Apis dorsata deposited maximum number of pollen grains per single visit. Insect pollinators and flowering plants have co-evolved together for millions of years, developing a wide array of mutualistic interactions. Several cultivated plant species depend exclusively on insect-mediated pollination services for their subsistence, reproduction and survival. Radish, Raphanus raphanistrum subsp. sativus , a popular edible root vegetable (Family: Brassicaceae) completely depends on pollinators as self-pollination is totally absent due to sporophytic self-incompatibility. The present study was conducted at the experimental fields of the ICAR-Indian Institute of Horticultural Research, Bengaluru, to understand the diversity and foraging behaviour of insect pollinators in R. sativus . Continuous survey during the flowering period revealed that a total of fifteen insect species that belong to three insect orders (Hymenoptera, Diptera and Lepidoptera) were found to visit R. sativus flowers. The most abundant species was Apis florea L., followed by Apis dorsata F . , Tetragonula iridipennis (Smith), Apis cerana F., Lassioglossum sp. and Ischiodon scutellaris F. Floral visitors differed significantly in terms of their visitation frequency, with A. florea (0.76 ± 0.22 visits/flower/ min) being the most frequent visitor followed by A. dorsata (0.66 ± 0.21 visits/flower/ min) and T. iridipennis (0.59 ± 0.14 visits/flower/30 min). The maximum visitation rate was recorded for A. dorsata (7.8 ± 1.40 flowers visited/min) followed by A. cerana (6 ± 1.15). The maximum stay time on individual flower was recorded for Lassioglossum sp. (48.2 ± 3.67 sec) followed by T. iridipennis (44.2 ± 4.24 sec). The maximum numbers of pollen grains were deposited by A. dorsata (206.70 ± 56.45) followed by A. cerana (151.20 ± 31.84). All the floral visitors except A. florea made contact with stigma on every single visit (100 %). While, only 53 per cent of total visitation by the Apis florea led to stigma contact. Further, nectar robbing behaviour was majorly exhibited by A. florea and Delta conoideum compared to all other insect pollinators observed. Based on the overall pollinator effectiveness per day A. dorsata was found to be the most effective single pollinator species.

Windborne migration amplifies insect-mediated pollination services.

Worldwide, hoverflies (Syrphidae: Diptera) provide crucial ecosystem services such as pollination and biological pest control. Although many hoverfly species exhibit migratory behavior, the spatiotemporal facets of these movement dynamics, and their ecosystem services implications are poorly understood. In this study, we use long-term (16-year) trapping records, trajectory analysis, and intrinsic (i.e., isotope, genetic, pollen) markers to describe migration patterns of the hoverfly Episyrphus balteatus in northern China. Our work reveals how E. balteatus migrate northward during spring-summer and exhibits return (long-range) migration during autumn. The extensive genetic mixing and high genetic diversity of E. balteatus populations underscore its adaptive capacity to environmental disturbances, for example, climate change. Pollen markers and molecular gut analysis further illuminate how E. balteatus visits min. 1012 flowering plant species (39 orders) over space and time. By thus delineating E. balteatus transregional movements and pollination networks, we advance our understanding of its migration ecology and facilitate the design of targeted strategies to conserve and enhance its ecosystem services.

Anthropogenic air pollutants reduce insect-mediated pollination services

Common air pollutants, such as nitrogen oxides (NOx), emitted in diesel exhaust, and ozone (O3), have been implicated in the decline of pollinating insects. Reductionist laboratory assays, focused upon interactions between a narrow range of flowering plant and pollinator species, in combination with atmospheric chemistry models, indicate that such pollutants can chemically alter floral odors, disrupting the cues that foraging insects use to find and pollinate flowers. However, odor environments in nature are highly complex and pollination services are commonly provided by suites of insect species, each exhibiting different sensitivities to different floral odors. Therefore, the potential impacts of pollution-induced foraging disruption on both insect ecology, and the pollination services that insects provide, are currently unknown. We conducted in-situ field studies to investigate whether such pollutants could reduce pollinator foraging and as a result the pollination ecosystem service that those insects provide. Using free-air fumigation, we show that elevating diesel exhaust and O3, individually and in combination, to levels lower than is considered safe under current air quality standards, significantly reduced counts of locally-occurring wild and managed insect pollinators by 62–70% and their flower visits by 83–90%. These reductions were driven by changes in specific pollinator groups, including bees, flies, moths and butterflies, and coincided with significant reductions (14–31%) in three different metrics of pollination and yield of a self-fertile test plant. Quantifying such effects provides new insights into the impacts of human-induced air pollution on the natural ecosystem services upon which we depend.

Floral traits and community phylogenetic structure shape plant-pollinator interactions in co-occurring Rhododendrons in the Himalaya

Elevation gradients of mountains serve as ideal settings to test the impact of pollinators on plant community assemblages. A shift from bird to insect-mediated pollination is expected with an increase in elevation, and such biotic shifts become more prominent in transition zones or ecotones. This shift in pollinator communities may influence plant communities if pollinators select plants with a specific set of floral traits and flowering phenology to maximize their floral resource (nectar) acquisition. However, empirical studies that examine the relative role of pollinator interactions (such as facilitation and competition) in the assembly of plant communities along elevation gradients are limited. Here we use an integrative framework combining floral traits, pollinators, flowering phenology and community phylogenetic data to reveal the relative role of facilitative and competitive interactions in the assembly of Rhododendron communities along elevation gradients in the Sikkim Himalaya. We find evidence that at lower elevations the Rhododendron community is structured by both facilitation and competition. In contrast, communities in the transition zone and at higher elevations are structured by competition alone. In lower elevations, corolla length, followed by the start of flowering phenology and nectar volume, showed significant phenotypic clustering and supported the facilitation while all other traits were overdispersed, suggesting the role of competition. Furthermore, a clustered phylogenetic structure was predominately observed at lower-elevation Rhododendron communities. In comparison, a dispersed and random phylogenetic structure was observed in the transition zone and at higher elevations. We observed greater overlap in flowering phenology and less pollinator similarity in lower elevation communities, compared to those in higher reaches.We suggest that in the Himalaya, even at small spatial scales, indirect biotic interactions may significantly contribute to the assembly of interdependent alpine plant communities. Overall, our findings highlight the importance of considering plant-pollinator interactions as important drivers when evaluating plant community assembly processes.

Nocturnal Pollinators Significantly Contribute to Apple Production.

Agricultural dependency on insect-mediated pollination is increasing at the same time that pollinator populations are experiencing declines in diversity and abundance. Current pollinator research in agriculture focuses largely on diurnal pollinators, yet the evidence for pollination by moths and other nocturnal pollinators is growing. Apples are one of the most valuable and important fruits produced globally, and apple production is dependent on insect-mediated cross-pollination to generate a profitable crop. We examined contributions to apple production provided by nocturnal insects via an exclusion experiment. We compared the relative contributions to apple production provided by nocturnal and diurnal pollinators using fruit set, the likelihood of cluster pollination, and seed set. We found nocturnal pollinators capable of facilitating the production of as many apples at similar levels of pollination as diurnal pollinators. We further found evidence that nocturnal and diurnal pollinators pollinate synergistically, with pollination contributions being additive in one year of our study. Our research identifies significant contributions to apple production provided by nocturnal pollinators, which may interact with diurnal pollinators in ways that are currently unrecognized. Expansions of this research into additional pollinator-dependent crops and focused investigations on specific nocturnal insects will provide more accurate assessments of nocturnal-pollinator roles in agriculture and improve our overall understanding of pollination in agriculture.

Pollination ecology and breeding systems of Cypripedium kentuckiense (Orchidaceae) in Tennessee1

The orchid Cypripedium kentuckiense is listed as imperiled in Tennessee and Oklahoma and critically imperiled in seven other states. We followed individuals' vegetative and floral traits over two seasons. Patterns of floral senescence were found to vary over two seasons and might be related to April temperatures when buds develop. Mechanical self-pollination was uncommon but perhaps “leaky.” Frequencies of insect-mediated pollination were surprisingly high (62%) for a Cypripedium species with large flowers but conversion of flowers into fruit was low (7% and 14%), suggesting that cryptic factors lower reproductive success, not inadequate pollinator visits. Hand-pollinations suggest flowers are self-compatible. As in other Cypripedium species, floral architecture relates to pollinator dimensions but at this site, only two bee species, Anthophora abrupta and A. bomboides, were primary pollinators. Male A. abrupta were common visitors although male bees are uncommon pollen vectors of Cypripedium species. For the first time, exit patterns of bees inside Cypripedium flowers were recorded based on bee species and gender. This behavior varied and was somewhat atypical of previous studies on other bee-pollinated species in the clade and genus. Specifically, Anthophora species within labella chewed on the epidermis lingering within the interior and exit canals. Consequently, C. kentuckiense might not be a trap.

Economic Dependence and Vulnerability of United States Agricultural Sector on Insect-Mediated Pollination Service.

Deficits in insect-mediated pollination service undermine ecosystem biodiversity and function, human nutrition, and economic welfare. Global pollinator supply continues to decline, while production of pollination-dependent crops increases. Using publicly available price and production data and existing pollination field studies, we quantify economic dependence of United States crops on insect-mediated pollination service at the county level and update existing coefficients of insect dependence of sample crops when possible. Economic value dependent on pollination service totals 34.0 billion USD in 2012. Twenty percent of US counties produce 80% of total economic value attributable to insect pollinators. We compile county-level data and consider the spatial relationship between economic value dependent on insect-mediated pollination, region-specific forage suitability, and crop-specific agricultural areas within US landscapes. We identify vulnerable, highly dependent areas where habitat for wild pollinators has been reduced. These results can help inform future efforts to conserve and bolster managed and wild pollinator populations to ensure sustainable production of key agricultural crops.

The floral ecology and breeding system of Veratrum virginicum (Melanthiaceae)1

We analyzed the floral biology of a population of the threatened/endangered Veratrum virginicum (L.) W.T. Aiton at the Shaw Nature Reserve (Missouri, USA), comparing our results to the first and only study of this species by Charles Robertson (1896). We confirmed most of Robertson's original descriptions regarding floral presentation, protandry, and insect pollination but found the following new information. Each flower lived 9–11 days and smelled of raw liver and latex. We discerned four floral stages based on gradual changes in style and stamen orientation, which might assist in insect-mediated pollination. We determined that stigmas became receptive by the fifth day of anthesis. The generalist pollination system included three Lasioglossum species (Halictidae) and the beetle Chauliognathus marginatus Fabr. (Cantharidae). Most floral foragers showed a geometric mean of body dimensions between 2–3 mm. Approximately 40% of foraging insects carried heterospecific pollen loads, combining the host flower's pollen with grains from up to seven co-blooming taxa. Field observations suggest that all bees foraged on multiple inflorescences whereas beetles remained on the same inflorescence for hours. Larger Apidae species showed symptoms of nectar poisoning. Epifluorescence showed that flowers exposed to visiting insects contained < 5 pollen tubes per gynoecium. Fruit set was 3% for bagged flowers and 51% for exposed flowers. However, the conversion rate of ovules into seeds was low in both bagged (2%) and exposed (6%) flowers. We interpret low reproductive success as one explanation for current declines in populations of this species.