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Seventy five percent of the world's food crops benefit from insect pollination. Hence, there has been increased interest in how global change drivers impact this critical ecosystem service. Because standardized data on crop pollination are rarely available, we are limited in our capacity to understand the variation in pollination benefits to crop yield, as well as to anticipate changes in this service, develop predictions, and inform management actions. Here, we present CropPol, a dynamic, open, and global database on crop pollination. It contains measurements recorded from 202 crop studies, covering 3,394 field observations, 2,552 yield measurements (i.e., berry mass, number of fruits, and fruit density [kg/ha], among others), and 47,752 insect records from 48 commercial crops distributed around the globe. CropPol comprises 32 of the 87 leading global crops and commodities that are pollinator dependent. Malus domestica is the most represented crop (32 studies), followed by Brassica napus (22 studies), Vaccinium corymbosum (13 studies), and Citrullus lanatus (12 studies). The most abundant pollinator guilds recorded are honey bees (34.22% counts), bumblebees (19.19%), flies other than Syrphidae and Bombyliidae (13.18%), other wild bees (13.13%), beetles (10.97%), Syrphidae (4.87%), and Bombyliidae (0.05%). Locations comprise 34 countries distributed among Europe (76 studies), North America (60), Latin America and the Caribbean (29), Asia (20), Oceania (10), and Africa (7). Sampling spans three decades and is concentrated on 2001-2005 (21 studies), 2006-2010 (40), 2011-2015 (88), and 2016-2020 (50). This is the most comprehensive open global data set on measurements of crop flower visitors, crop pollinators and pollination to date, and we encourage researchers to add more datasets to this database in the future. This data set is released for non-commercial use only. Credits should be given to this paper (i.e., proper citation), and the products generated with this database should be shared under the same license terms (CC BY-NC-SA)., (© 2021 The Ecological Society of America.)

Wild and managed bees are well documented as effective pollinators of global crops of economic importance. However, the contributions by pollinators other than bees have been little explored despite their potential to contribute to crop production and stability in the face of environmental change. Non-bee pollinators include flies, beetles, moths, butterflies, wasps, ants, birds, and bats, among others. Here we focus on non-bee insects and synthesize 39 field studies from five continents that directly measured the crop pollination services provided by non-bees, honey bees, and other bees to compare the relative contributions of these taxa. Non-bees performed 25-50% of the total number of flower visits. Although non-bees were less effective pollinators than bees per flower visit, they made more visits; thus these two factors compensated for each other, resulting in pollination services rendered by non-bees that were similar to those provided by bees. In the subset of studies that measured fruit set, fruit set increased with non-bee insect visits independently of bee visitation rates, indicating that non-bee insects provide a unique benefit that is not provided by bees. We also show that non-bee insects are not as reliant as bees on the presence of remnant natural or seminatural habitat in the surrounding landscape. These results strongly suggest that non-bee insect pollinators play a significant role in global crop production and respond differently than bees to landscape structure, probably making their crop pollination services more robust to changes in land use. Non-bee insects provide a valuable service and provide potential insurance against bee population declines.

Recent concern over global pollinator declines has led to considerable research on the effects of pesticides on bees. Although pesticides are typically not encountered at lethal levels in the field, there is growing evidence indicating that exposure to field-realistic levels can have sublethal effects on bees, affecting their foraging behaviour, homing ability and reproductive success. Bees are essential for the pollination of a wide variety of crops and the majority of wild flowering plants, but until now research on pesticide effects has been limited to direct effects on bees themselves and not on the pollination services they provide. Here we show the first evidence to our knowledge that pesticide exposure can reduce the pollination services bumblebees deliver to apples, a crop of global economic importance. Bumblebee colonies exposed to a neonicotinoid pesticide provided lower visitation rates to apple trees and collected pollen less often. Most importantly, these pesticide-exposed colonies produced apples containing fewer seeds, demonstrating a reduced delivery of pollination services. Our results also indicate that reduced pollination service delivery is not due to pesticide-induced changes in individual bee behaviour, but most likely due to effects at the colony level. These findings show that pesticide exposure can impair the ability of bees to provide pollination services, with important implications for both the sustained delivery of stable crop yields and the functioning of natural ecosystems.

One major characteristic of invasive alien species is their occurrence at high abundances in their new habitat. Flowering invasive plant species that are visited by native insects and overlap with native plant species in their pollinators may facilitate or disrupt native flower visitation and fertilisation by forming large, dense populations with high numbers of flowers and copious rewards. We investigated the direction of such a proposed effect for the alien invasive Rhododendron ponticum in Irish habitats. Flower visitation, conspecific and alien pollen deposition, fruit and seed set were measured in a self-compatible native focal plant, Digitalis purpurea, and compared between field sites that contained different relative abundances of R. ponticum. Flower visitation was significantly lower at higher alien relative plant abundances than at lower abundances or in the absence of the alien. Native flowers experienced a significant decrease in conspecific pollen deposition with increasing alien abundance. Heterospecific pollen transfer was very low in all field sites but increased significantly with increasing relative R. ponticum abundance. However, lower flower visitation and lower conspecific pollen transfer did not alter reproductive success of D. purpurea. Our study shows that indirect interactions between alien and native plants for pollination can be modified by population characteristics (such as relative abundance) in a similar way as interactions among native plant species. In D. purpurea, only certain aspects of pollination and reproduction were affected by high alien abundances which is probably a result of high resilience due to a self-compatible breeding system. Native species that are more susceptible to pollen limitation are more likely to experience fitness disadvantages in habitats with high relative alien plant abundances.

Flowers act as "sensory billboards" with multiple signals (color, morphology, odor) attracting and manipulating potential pollinators. Many use changing signals as indicators that visitation and/or pollination have occurred). Floral color change is commonly used to transmit this information (often correlated with reduced nectar reward) and can be specifically triggered by pollination or visitation. By retaining color-changed flowers, plants benefit from larger floral displays but also indicate at close range which flowers are still rewarding (and still unpollinated), so that visitors forage more efficiently. However, the legume Desmodium setigerum shows a unique ability, if inadequately pollinated, to reverse its flowers' color and shape changes. Single visits by bees mechanically depress the keel and expose stigma and anthers (termed "tripping"); visits also initiate a rapid color change from lilac to white and turquoise and a slower morphological change, the upper petal folding downwards over the reproductive parts. But flowers receiving insufficient pollen can partially reopen, re-exposing the stigma, with a further color change to deeper turquoise and/or lilac. Thus, most flowers achieve pollination from one bee visit, but those with inadequate pollen receipt can reverse their signals, earning a "second chance" by eliciting attention from other potential pollinators.

Human land use threatens global biodiversity and compromises multiple ecosystem functions critical to food production. Whether crop yield-related ecosystem services can be maintained by a few dominant species or rely on high richness remains unclear. Using a global database from 89 studies (with 1475 locations), we partition the relative importance of species richness, abundance, and dominance for pollination; biological pest control; and final yields in the context of ongoing land-use change. Pollinator and enemy richness directly supported ecosystem services in addition to and independent of abundance and dominance. Up to 50% of the negative effects of landscape simplification on ecosystem services was due to richness losses of service-providing organisms, with negative consequences for crop yields. Maintaining the biodiversity of ecosystem service providers is therefore vital to sustain the flow of key agroecosystem benefits to society.

Quantifying the contributions of insect pollinators to crops provides insight into how pollination services should be managed and protected into the future.Faba bean, Vicia faba var minor (Linneaus), is a widely grown crop globally that can benefit from pollinator visitation, but only from species that are morphologically compatible with the plant's long‐corollae flowers. Here, we rank insect pollinators in terms of their potential importance to faba bean pollination and quantify the economic value of pollination for Irish faba beans.Our findings demonstrate that bee pollination contributes significantly to the pod set of faba beans, and, consequently, the crop's production value. We find that pollination services account for almost half of Ireland's total faba bean market value, with the pollinator contribution estimated at almost €4,000,000 per year.We estimate that, relative to other pollinators, wild bumblebees contribute to approximately 70% of the economic value of pollination services in faba bean fields, driven mainly by the contributions of a long‐tongued bumblebee species, Bombus hortorum (Linneaus; Hymenoptera: Apidae).Based on these results, we suggest that B. hortorum populations be encouraged on farmland through appropriate management to ensure the continued delivery of pollination services to Irish faba beans. [ABSTRACT FROM AUTHOR]

1. Managing farmland to benefit biodiversity is becoming increasingly necessary to combat biodiversity declines and maintain ecosystem services. Results-based agri-environmental schemes are a tool used to achieve this by paying farmers based on environmental results delivered. These schemes often utilise plant indicator species to assess results at field scale; however, it is unknown if focusing on enhancing a subset of one biodiversity group within results-based schemes impacts wider biodiversity, and whether local-scale implementation of results-based schemes or/and the wider landscape are more important drivers of biodiversity patterns. 2. Insect pollinators provide important pollination services for many crop and wild plants, and as mobile organisms often experience landscape at large spatial scales. We tested whether insect pollinators are affected at local scale by a results-based scheme scored based on plant indicators, or if landscape management is more important, and whether there were different responses between taxon-specific groups. Bumblebees, solitary bees, hoverflies and butterflies were sampled using transects and pan traps in 23 fields with varying scores assigned by the scheme, situated in high-intensity (≥65% improved grassland) or low-intensity (≥65% seminatural grassland) landscapes. 3. Results indicate taxon-specific responses to local and landscape management in semi-natural grasslands. Bumblebees responded positively to local-scale management in fields with higher floral diversity, whereas hoverflies and butterflies responded positively to low-intensity landscape management. 4. Synthesis and applications. Using plant species as indicators for biodiversity in agri-environment schemes can have indirect benefits for non-target taxa like bumblebees, but broader indicators should be developed to incorporate other pollinator groups. Pollinator groups respond differently to local and landscape management in semi-natural grasslands. Agri-environmental management should consider a range of different management measures and landscape scale approaches where possible, to maximise benefits for a range of pollinator taxa. [ABSTRACT FROM AUTHOR]

Western honeybees (Apis mellifera L.), native to Europe and Africa, have been transported worldwide and are now one of the most important global crop pollinator species. Although the relative contribution of honeybees to global crop pollination is increasingly recognized, relatively little is known about their importance as pollinators in wild plant communities. The only remaining wild and unmanaged western honeybee populations are in Africa. We investigated the importance of honeybees as pollinators of diverse wild plant communities in two protected areas within the Maputaland-Pondoland-Albany biodiversity hotspot in South Africa. Sites were far from any known areas of beekeeping, and so all honeybees were most likely from wild colonies. Honeybees visited a large proportion of flowering plant species within these two communities (40% and 35%) and also provided a substantial proportion of visits to the plants they visited (40% and 32%, respectively). However, when pollinator importance indices (based on abundance and the size and purity of pollen loads) were calculated for a small subset of plants, honeybees were only important pollinators of 29% of the plants they visited. Our data provide a first step in determining the importance of honeybees as flower visitors and pollinators in wild plant communities and the potential impacts of honeybee declines on these highly diverse grassland ecosystems. Our work suggests that many plants in the grassland systems studied are visited by non-Apis flower visitors and therefore that conservation efforts should also focus on these pollinator groups. [ABSTRACT FROM AUTHOR]

Proboscis length has been proposed as a key dimension of plant pollination niches, but this niche space has not previously been explored at regional and global scales for any pollination system. Hawkmoths are ideal organisms for exploring pollinator niches as they are important pollinators in most of the biodiverse regions of the earth and vary greatly in proboscis length, with some species having the longest proboscides of all insects., Using data sets for nine biogeographical regions spanning the Old and New World, we ask whether it is possible to identify distinct hawkmoth pollination niches based on the frequency distribution of proboscis length, and whether these niches are reflected in the depths of flowers that are pollinated by hawkmoths. We also investigate the levels of specialization in hawkmoth pollination systems at the regional and community level using data from interaction network studies., We found that most regional hawkmoth assemblages have bimodal or multimodal distributions of proboscis length and that these are matched by similar distributions of floral tube lengths. Hawkmoths, particularly those with longer proboscides, are polyphagous and at the network level show foraging specialization equivalent to or less than that of bees and hummingbirds. In the case of plants, shorter-tubed flowers are usually visited by numerous hawkmoth species, while those that are longer-tubed tend to exclude shorter-proboscid hawkmoths and thus become ecologically specialized on longer-proboscid hawkmoth species. Longer-tubed flowers tend to have greater nectar rewards, and this promotes short-term constancy by long-proboscid hawkmoths., Our results show that pollinator proboscis length is a key niche axis for plants and can account for the patterns of evolution in functional traits such as floral tube length and nectar volume. We also highlight a paradoxical trend for nectar resource niche breadth to increase according to proboscis length of pollinators, while pollinator niche breadth decreases according to the tube length of flowers., A is available for this article. [ABSTRACT FROM AUTHOR]

Increasingly, the importance of both varietal and regional variation in crop pollination requirements is becoming apparent in terms of informing the management of crop pollination services. Apples are an economically important crop pollinated by both wild and managed insects, but evidence suggests that insect groups can differ in their contributions to apple pollination between both regions and varieties. To address the increasing need for a more context-specific understanding of crop pollination, we assessed the pollinator importance of different insect guilds and pollinator dependence of two apple cultivars widely grown in Ireland: Jonagored and Dabinett. We found that insect pollination differentially increased the yield and economic profit of both cultivars, contributing to 93% of Jonagored market value and 46% of Dabinett market value, equating to over €800,000 per year to their combined production in Ireland. We also found that, while honeybees, bumblebees, solitary bees, and hoverflies all contribute to the pollination of apples, these contributions differ between guilds and apple cultivars. Our results suggest that honeybees and bumblebees are the most important pollinators of Jonagored apples, while honeybees contribute the most to Dabinett pollination. Honeybee visitation rates vary considerably between cultivars, suggesting the need to insure pollination services through land management strategies that prioritize maintaining and increasing wild insect diversity. Increasing hoverfly and solitary bee abundance may be good targets for future pollinator management since we found that hoverflies exhibit high abundances and floral visitation rates and that solitary bees transport large amounts of apple pollen, despite their low abundance. Our work shows varietal differences in the pollination requirements of regionally-specific, within-crop cultivars, thus confirming the need for a more comprehensive understanding of crop pollination requirements at varietal and regional levels to ensure appropriate pollinator conservation and pollination management. • Insect pollination is an economically valuable service for apple production. • Fruit and seed set in Irish apple cultivars are enhanced with insect pollination. • Insect pollinator guilds vary in terms of their contributions to apple pollination. • Wild pollinating insects provide a considerable amount of pollination services. • Services of some pollinator guilds may be enhanced with appropriate management. [ABSTRACT FROM AUTHOR]