Provide Pollination Services Research Articles

Insecticide and low food quality treatments reduce health and pollination services of two key pollinator taxa

Abstract Pesticides and the lack of floral resources are key drivers of insect decline in agricultural areas. Both land‐use stressors can have a variety of synergistic and sublethal effects on pollinators, affecting their health and foraging behaviour. Pollinating insects include species with vastly different life histories, giving them potentially different vulnerability and resilience to stressors. However, most research has generally focused on bees. Here, we contrast synergistic effects of nutritional stress and pesticide use on social bumblebees and solitary hoverflies. We experimentally tested the effects of the neonicotinoid acetamiprid and low‐quality food on health traits of Bombus terrestris workers and Episyrphus balteatus adults (ovarian development, body size and colony development or survival). The foraging behaviour of treated pollinators was recorded in a semi‐field setup and, for B. terrestris, we measured the pollen amount on the body surface and the pollen deposited on stigmata after a single floral visit. Both stressors affected bumblebee health. Additionally, insecticide‐treated workers showed increased flower handling times and flight durations, while low‐quality food reduced the amount of pollen on the surface of bumblebees and the pollen deposited on stigmata. Syrphids were mostly affected by low‐quality food, which decreased their survival probability and changed their foraging behaviour. Furthermore, we found an interactive effect between the two stressors, reducing E. balteatus ovary development. Synthesis and applications. Insecticide and food stress affected fitness traits of both bumblebees and syrphid flies, possibly reducing pollinator populations under natural conditions. Especially for bumblebees, long‐term exposure led to a reduction in the provision of pollination services, both by changing their behaviour and reducing pollen transfer. We found differences between the two pollinator groups, showing that results gained from single groups like bees should not be extrapolated to all pollinators. Interactive effects indicate potential buffering effects of high‐quality food against other stressors and highlight the importance of considering synergies between multiple stressors in risk assessments. This further emphasizes the relevance of floral resources such as wild flower strips in agricultural areas to conserve pollinators and pollination services.

Pollinator diversity, pollination services, and conservation in agroecosystems: A mini‐review on the successes and challenges in China

AbstractPollinators provide important pollination services for crops around the world. In China, numerous studies have been conducted on pollinators within agroecosystems, yet a comprehensive review of such research remains to be completed. This study discusses the existing knowledge of pollinator diversity in Chinese agroecosystems, examines the provision of pollination services, and identifies key achievements and limitations. We propose a series of conservation and management actions to promote pollinator health and ecosystem services in these agroecosystems: (1) long‐term monitoring of pollinator populations, (2) designing agricultural landscapes that are conducive to pollinators, and (3) implementing microscale habitat modifications to improve conditions for pollinators.

Different Sensitivity of Flower-Visiting Diptera to a Neonicotinoid Insecticide: Expanding the Base for a Multiple-Species Risk Assessment Approach.

Insects play an essential role as pollinators of wild flowers and crops. At the same time, pollinators in agricultural environments are commonly exposed to pesticides, compromising their survival and the provision of pollination services. Although pollinators include a wide range of species from several insect orders, information on pesticide sensitivity is mostly restricted to bees. In addition, the disparity of methodological procedures used for different insect groups hinders the comparison of toxicity data between bees and other pollinators. Dipterans are a highly diverse insect order that includes some important pollinators. Therefore, in this study, we assessed the sensitivity of two hoverflies (Sphaerophoria rueppellii, Eristalinus aeneus) and one tachinid fly (Exorista larvarum) to a neonicotinoid insecticide (Confidor®, imidacloprid) following a comparative approach. We adapted the standardized methodology of acute contact exposure in honey bees to build dose-response curves and calculate median lethal doses (LD50) for the three species. The methodology consisted in applying 1 µL of the test solution on the thorax of each insect. Sphaerophoria rueppelli was the most sensitive species (LD50 = 10.23 ng/insect), and E. aeneus (LD50 = 18,176 ng/insect) the least. We then compared our results with those available in the literature for other pollinator species using species sensitivity distribution (SSD). Based on the SSD curve, the 95th percentile of pollinator species would be protected by a safety factor of 100 times the Apis mellifera endpoint. Overall, dipterans were less sensitive to imidacloprid than most bee species. As opposed to most bee species, oviposition and fecundity of many dipteran species can be reliably assessed in the laboratory. We measured the number of eggs laid following exposure to different insecticide doses and assessed the potential trade-off between oviposition and survival through the sublethal sensitivity index (SSI). Exposure to imidacloprid had a significant effect on fecundity, and SSI values indicated that oviposition is a sensitive endpoint for the three dipteran species tested. Future studies should integrate this information related to population dynamics in simulation models for environmental risk assessment.

Vertical Stratification of Solitary Bees and Wasps in an Urban Forest from the Brazilian Amazon.

Solitary bees and wasps that nest in cavities in tree trunks are important components of terrestrial ecosystems, providing pollination services, and in the case of wasps, the regulation of their prey populations. However, little is known about the vertical strata where bees and wasps build their nests. This is especially the case of urban forest remnants in the Amazon, which is relevant in the context of the global crisis in insect losses. We investigated the existence of vertical stratification in the nesting of solitary bees and wasps in an urban forest in Rio Branco, state of Acre, in the western Brazilian Amazon. We focused on whether wood temperature, ants, and termites are predictors of bee and wasp nesting. We sampled bee and wasp nests in the forest using trap-nests made with wooden blocks containing cavities with three different diameters for twelve months. Trap-nests were installed randomly at three heights in the forest. We collected 145 nests of 25 species, belonging to 11 genera and 6 families. A higher number of nests and species were collected in the upper stratum of the forest, strengthening the hypothesis that there is vertical stratification in the assemblage of solitary bees and wasps. Wood surface temperature and termite attacks on trap-nests were significantly different between strata, which may explain the vertical stratification of bee and wasp assemblages. Considering the importance of these insects for tropical forest ecosystems, the conservation of structurally complex and stratified forests is of paramount importance to maintain the diversity of this insect group.

Intercropping Industrial Hemp and Cowpea Enhances the Yield of Squash—A Pollinator-Dependent Crop

Cultural crop-production practices are not only engineered to minimize pest incidence but also improve resource use efficiency and increase the diversity of habitat for beneficial insects that provide pollination services. With the increasing cultivation of industrial hemp and the benefits associated with the cultivation of multiple crops, its integration into a polyculture cropping system remains to be evaluated. We intercropped two pollinator-attractive crops, hemp and cowpea, with squash, a pollinator-dependent crop, to evaluate the impact of pollinator abundance and diversity on crop yield. Intercropping significantly increased the overall abundance of pollinators with 79.1% recorded from the intercropping systems compared to 21.9% in the monocropping systems. Sweat bees and bumble bees were the most abundant bees, and Squash+Cowpea was the most diverse cropping system. Intercropping significantly increased the yield of squash with higher squash yield (155%) in Hemp+Squash and (161%) in Squash+Cowpea than in squash monocrop. Also, intercropping resulted in higher hemp yield (64%) in Hemp+Cowpea and (165%) in Hemp+Squash compared to hemp monocrop. This study demonstrated that agricultural systems such as intercropping that are designed to attract pollinators are much more productive by not only improving crop yield but also growers’ returns on investments.

Discovery and characterization of novel DNA viruses in Apis mellifera: expanding the honey bee virome through metagenomic analysis.

To date, many viruses have been discovered to infect honey bees. In this study, we used high-throughput sequencing to expand the known virome of the honey bee, Apis mellifera, by identifying several novel DNA viruses. While the majority of previously identified bee viruses are RNA, our study reveals nine new genomes from the Parvoviridae family, tentatively named Bee densoviruses 1 to 9. In addition, we characterized a large DNA virus, Apis mellifera filamentous-like virus (AmFLV), which shares limited protein identities with the known Apis mellifera filamentous virus. The complete sequence of AmFLV, obtained by a combination of laboratory techniques and bioinformatics, spans 152,678 bp. Linear dsDNA genome encodes for 112 proteins, of which 49 are annotated. Another large virus we discovered is Apis mellifera nudivirus, which belongs to a group of Alphanudivirus. The virus has a length of 129,467 bp and a circular dsDNA genome, and has 106 protein encoding genes. The virus contains most of the core genes of the family Nudiviridae. This research demonstrates the effectiveness of viral binning in identifying viruses in honey bee virology, showcasing its initial application in this field.IMPORTANCEHoney bees contribute significantly to food security by providing pollination services. Understanding the virome of honey bees is crucial for the health and conservation of bee populations and also for the stability of the ecosystems and economies for which they are indispensable. This study unveils previously unknown DNA viruses in the honey bee virome, expanding our knowledge of potential threats to bee health. The use of the viral binning approach we employed in this study offers a promising method to uncovering and understanding the vast viral diversity in these essential pollinators.

Toxicity and Risk of Biopesticides to Insect Pollinators in Urban and Agricultural Landscapes

Pollinators play important roles in providing pollination services, maintaining biodiversity, and boosting crop production. Even though pollinators are essential to the environment and agriculture, their decline has been noted across multiple studies in the recent past. Both natural and anthropogenic factors have contributed to their decline. Much of the focus has been placed on climate change, habitat loss, pests and pathogens, and synthetic pesticides, but relatively little is known about the effects of biopesticides. Biopesticides are biological control agents derived from living organisms and are classified into three groups: microbial, biochemical, and plant-incorporated protectant-based products. Biopesticides are formulated similarly to their synthetic counterparts and are readily available and used within urban and agricultural settings by pest management experts and household residents. The general public and much scientific literature support the prevailing idea that biopesticides are environmentally safe and pollinator friendly in comparison with synthetic versions. However, such generalizations are based on studies with a few key pollinator species and may not be relevant to several other species that provide crop pollination services. Studies focused on native pollinators have shown that some biopesticides have lethal and sublethal effects. Because each biopesticide exhibits varying effects across pollinator species, it could be dangerous to generalize their non-toxicity across taxa and environmental settings. In this article, recent research in this direction is discussed.

Distinct fungal microbiomes of two Thai commercial stingless bee species, Lepidotrigona terminata and Tetragonula pagdeni suggest a possible niche separation in a shared habitat.

Stingless bees, a social corbiculate bee member, play a crucial role in providing pollination services. Despite their importance, the structure of their microbiome, particularly the fungal communities, remains poorly understood. This study presents an initial characterization of the fungal community associated with two Thai commercial stingless bee species, Lepidotrigona terminata (Smith) and Tetragonula pagdeni (Schwarz) from Chiang Mai, Thailand. Utilizing ITS amplicon sequencing, we identified distinct fungal microbiomes in these two species. Notably, fungi from the phyla Ascomycota, Basidiomycota, Mucoromycota, Mortierellomycota, and Rozellomycota were present. The most dominant genera, which varied significantly between species, included Candida and Starmerella. Additionally, several key enzymes associated with energy metabolism, structural strength, and host defense reactions, such as adenosine triphosphatase, alcohol dehydrogenase, β-glucosidase, chitinase, and peptidylprolyl isomerase, were predicted. Our findings not only augment the limited knowledge of the fungal microbiome in Thai commercial stingless bees but also provide insights for their sustainable management through understanding their microbiome.

Systemic pesticides in a solitary bee pollen food store affect larval development and increase pupal mortality

Solitary bees are often exposed to various pesticides applied for pest control on farmland while providing pollination services to food crops. Increasing evidence suggests that sublethal toxicity of agricultural pesticides affects solitary bees differently than the social bees used to determine regulatory thresholds, such as honey bees and bumblebees. Studies on solitary bees are challenging because of the difficulties in obtaining large numbers of eggs or young larvae for bioassays. Here we show the toxic and sublethal developmental effects of four widely used plant systemic pesticides on the Japanese orchard bee (Osmia cornifrons). Pollen food stores of this solitary bee were treated with different concentrations of three insecticides (acetamiprid, flonicamid, and sulfoxaflor) and a fungicide (dodine). Eggs were transplanted to the treated pollen and larvae were allowed to feed on the pollen stores after egg hatch. The effects of chronic ingestion of contaminated pollen were measured until adult eclosion. This year-long study revealed that chronic exposure to all tested pesticides delayed larval development and lowered larval and adult body weights. Additionally, exposure to the systemic fungicide resulted in abnormal larval defecation and increased mortality at the pupal stage, indicating potential risk to bees from fungicide exposure. These findings demonstrate potential threats to solitary bees from systemic insecticides and fungicides and will help in making policy decisions to mitigate these effects.

Orchards closer to forest patches produced fewer malformed fruits and more commercial fruits: The importance of legitimate floral visitors

Mexico is the main mango exporter worldwide, making ‘Ataulfo’ one of the most preferred cultivars. However, fruit production has been drastically diminished due to the high incidence of malformed fruits, known as nubbins. One of the possible causes of this is the lack of pollinators, which are necessary to set developed fruits. Since many pollinators depend on forest patches, the proximity of mango orchards to these is expected to decrease the incidence of nubbins. However, no study has evaluated the effect of distance from forest patches on the production of malformed fruits in any mango cultivar. The present study evaluates the incidence of nubbins and the production of commercial fruits, as well as the richness, composition, and frequency of visits of legitimate floral visitors (i.e., those that contact both reproductive parts of the flowers) over two consecutive years on ‘Ataulfo’ mango orchards located at different distances from tropical dry forest patches. Our results indicate that mango orchards located closer to forest patches were visited more frequently and by more species of legitimate floral visitors, showed less incidence of nubbins, and had greater production of commercial fruits than those located further away from the forest patches. Moreover, we found that older mango trees and the absence of exotic honeybees are also key factors to increasing fruit production. Our results highlight the importance of the conservation of tropical dry forest patches to ensure the provision of pollination services and to maintain or increase the production of mango orchards.

РОЛЬ БДЖІЛЬНИЦТВА В ДОСЯГНЕННІ СТАЛОГО РОЗВИТКУ АГРАРНИХ ПІДПРИЄМСТВ ТА СІЛЬСЬКИХ ТЕРИТОРІЙ

The improvement of the economic performance of agricultural enterprises should not be accompanied by the deterioration of the quality of the environment and cause social tension among the employees of the enterprise and the population living in the surrounding area. Therefore, the problem arose of finding such directions of development of agricultural enterprises that would simultaneously contribute to the improvement of financial and economic indicators of their activity, as well as ensure the sustainable development of both the enterprises themselves and the sustainable development of the surrounding rural areas. The article examines the positive value of the agricultural sector, in particular: production of products, creation of jobs, provision of foreign exchange revenues to the state budget, the possibility of providing services of unity with nature. However, it was noted that the agricultural industry has negative consequences of its activity, in particular: the deterioration of the quality of the soil, the increase in the level of plowing, the excessive use of chemical plant protection agents leads to an increase in the level of soil pollution, the death of representatives of the fauna, as well as an increase in the level of human illness. It is proposed to restore and develop the beekeeping industry in order to reorient the activities of the agrarian industry on the principles of sustainable development. Both existing agricultural enterprises and small peasant farms can be engaged in bee breeding. For agricultural enterprises, beekeeping is a direction of diversification that can bring additional income. For rural residents, beekeeping is a way to provide themselves with a workplace and to earn from the sale of beekeeping products and the provision of pollination services to agricultural enterprises, which will be able to sell their products as organic at higher prices. However, starting a beekeeping business requires significant investments, which are not at the disposal of small peasant farms. Therefore, they are suggested to join cooperatives. This will make it possible to carry out laboratory analysis, form large batches of honey and sell it at a higher price. The cooperative can also pack and process honey with possible independent export. In general, the development of the beekeeping industry will contribute to increasing the level of employment in rural areas and improving the ecological situation, which corresponds to the principles of sustainable development.

Food plants in Brazil: origin, economic value of pollination and pollinator shortage risk

Pollination is a key ecosystem service of critical importance for food production. However, globally, several regions are already experiencing pollinator shortage as pollinators are declining. Here, we investigate the origin, pollinator dependence and economic value of 199 food crops cultivated in Brazil to understand to which extent (1) Brazilian agriculture is vulnerable to pollinator shortage, and (2) Brazilian society has already achieved a comprehensive perspective about crop dependence. We used Brazil as a case study as it is a megadiverse tropical country and the 3rd largest world crop producer and exporter, with most of the crops depending on pollinators. Our findings revealed that over half (53.7%) of the food crops in Brazil are native, with the North region of Brazil housing the higher diversity of native crops, in contrast with the South and Southeast regions. Additionally, considering the reproductive systems, among native food crops, 65.6% exhibit self-incompatibility or dioecy (i.e., requiring obligatory cross-pollination), whereas 30.6% of exotic food crops display this trait. Overall, Brazilian municipalities produce more exotic crops than native ones, with almost 4/5 of the total agricultural area of the country dedicated to the cultivation of exotic crops, which are generally self-compatible commodities that rely low to modestly on pollinators. Regarding the biomes, we observe that this pattern is followed by most of them, but for the Caatinga dry forest, where native crops dependent on pollinators predominate. However, when soybean is removed from the analysis, the areas devoted to exotic crops always decreased, even being equal to native crops in the Atlantic forest. Our results also indicate that considering the pollinator shortage, some Brazilian biomes may be at risk of losing >20% of their yields, mainly in the Caatinga dry forest and the Atlantic forest. Therefore, in this paper, we are discussing that the expansion of monocultures in Brazil's agricultural lands may have several impacts on the provision of pollination services, food production and, then, on food security not only for the Brazilian population, as Brazil is the 3rd largest world agricultural producer and exporter.

Exploring the External Environmental Drivers of Honey Bee Colony Development

Honey bees play an important role in agricultural landscapes by providing pollination services. Throughout the season, colonies increase their population and collect resources from the available flowering plants. Besides internal mechanisms, such as the amount of brood or the availability of bees to perform foraging flights, colonies are also influenced by the climate and the surrounding landscape. Therefore, exposure to different environmental contexts leads to distinct development rates. In this study, we show how colonies develop under three different landscape contexts and explore which external variables (mostly climate and resources availability) influence the colonies’ development. We installed three apiaries in three different landscapes in the Iberian Peninsula, with temporal and spatial variation in climatic conditions and resource availability. The availability of resources and their use, as well as the development of colonies throughout the season, were thoroughly investigated. These data were used to take the first step into creating an ecologically relevant landscape by calculating the number of available resources in the landscape at different points in time, based on plants’ beekeeping interest as well as nectar and production. Furthermore, climatic variables were transformed into the amount of available foraging minutes that bees had to collect resources, and a theoretical threshold of optimal vs. sub-optimal conditions was also explored. Interestingly, the main drivers of colony development (measured by daily weight increase) were not the same in the tested apiaries, evidencing how colonies are indeed intrinsically connected with the surrounding environmental scenario. Therefore, results from field testing are extremely context-dependent and should be interpreted with caution when being extrapolated to other environmental scenarios.

Distinct diurnal and nocturnal flower visitor communities provide pollination services in urban gardens

Abstract Urban gardens are considered a key tool for mitigating biodiversity and plant‐pollinator interaction loss due to their ubiquity in urban landscapes and the variety of resources they provide. To date, most urban garden pollination research has focused on diurnal pollination, omitting a potentially important group—nocturnal pollinators. To assess the diversity and pollination activity of both diurnal and nocturnal flower visitors in urban gardens, I monitored arthropods on focal inflorescences of Eupatorium perfoliatum, a common Michigan‐native species, for 24‐h cycles and recorded the number and duration of visits. I also measured diurnal and nocturnal communities' pollination services using a temporal floral visitation exclusion experiment. Flowers averaged nearly twice as many visits during the day as compared with night within 24‐h cycles, but nocturnal visit durations were 2.5‐fold longer on average. Day and night floral visitor communities were distinct, with day visits being dominated by Diptera, ants and other Hymenoptera, and night visits being carried out most frequently by ants, Dermaptera and Hemiptera. In the floral visitor exclusion experiment, plants open to only nocturnal visits produced larger seeds, whereas plants open to only diurnal visits trended towards producing more seeds, signalling a potential trade‐off between seed quantity and size among visitor communities. Overall, diurnal and nocturnal floral visitor communities were distinct, and nocturnally pollinated plants had reproductive output comparable to diurnally pollinated treatments. Given the emphasis on diurnal pollinators in most pollination studies, it is possible that relevant plant‐pollinator interaction information may be missed in cases where anthesis spans both day and night.

Pollen sources of Asian honeybee (Apis cerana Fabricius) in Paschim Medinipur district of West Bengal, India

The Asian honeybee (Apis cerana) occurs across the south, southeast and east Asia. The species is utilised in apicultural practices. But the available documents about their floral resources, especially pollen sources, are limited. However, it is a mandatory requirement in a sustainable honeybee management programme. In the present study, we conducted palynological analyses of pollen loads and field surveys to determine pollen sources for the honeybees in West Bengal, India. The honeybee species is regarded as a generalist forager with significant floral constancy supported by homogenous pollen loads with diverse pollen types (here 58). Important pollen-contributed plants were Acacia auriculiformis, Brassica juncea, Cocos nucifera, Eucalyptus sp., Neolamarckia cadamba, Peltophorum pterocarpum, Sesamum indicum and Tridax procumbens. In the semi-urban area of Midnapore town, honeybees mainly depend on planted trees and weeds for pollen sources. While in rural agricultural belts, they also visited wild trees and several cultivated crops. The bee-visited plants are diverse types regarding plant habits, flowering phenology and floral characteristics. These data will be helpful in the management of Asian honeybees, providing pollination services to cultivated crops and thereby enhancing crop yield.

Direct and indirect effects of urbanization, pesticides and wild insect pollinators on mango yield

Abstract Expanding cities increasingly encroach fertile farmlands, questioning the viability of maintaining agriculture within and around them. Yet, our knowledge on how urbanization influences pollinator communities and the provision of pollination services to crops is limited, especially for the urbanization hotspots of the Global South. Mango Mangifera indica is one of the most important fruit crops in tropical countries. To analyse the dependency of mango on its main insect pollinators, and the direct and indirect effects of urbanization and insecticides on pollinator abundance and mango yield, we conducted a pollinator exclusion experiment and sampled flower visitors on 16 mango farms spread across rural–urban landscapes in Bengaluru, a South Indian megacity. We found that allowing flowers access to ants and flying visitors (bees, hoverflies, nonsyrphid flies), dramatically increased mango yield by 350%, highlighting the importance of wild insects for mango pollination. We detected a trend between wild bee abundance and the final fruit set, with an increase of 20% when the number of bees increased from 25 to 125. Urbanization did not directly affect pollinator abundance or mango yield. However, the amount of insecticide applications had strong negative effects on wild bee abundance at low and intermediate levels of urbanization, while it had no effect in highly urbanized areas, presumably because of higher availability of flowering resources. Moreover, the amount of insecticides decreased the weight of harvested mango fruits by almost 30%. This may indicate trade‐offs between conventional pest control and enhanced crop yields through pollination by wild insects in rural areas. Synthesis and applications: Our results indicate that mango production can be maintained at a profitable level in urbanized landscapes with insect pollinators more than tripling final yield. However, increasing use of insecticides, besides raising farmers' expenses, can have negative effects on wild insect pollinators and mango yield, especially in rural areas. To safeguard crucial pollination services, it is therefore critical to conserve and promote wild insect pollinators by minimizing the negative effects of insecticide applications in these areas.

Mason bees and honey bees synergistically enhance fruit set in sweet cherry orchards

AbstractMason bees (Osmia spp.) are efficient fruit tree pollinators that can be encouraged to occupy and breed in artificial nesting material. In sweet cherry orchards, they are occasionally used as an alternative managed pollinator as a replacement for or in addition to honey bees (Apis mellifera). Yet, the lack of practical guidelines on management practices, for example optimal stocking rates, for both mason bee nesting material and honey bees might compromise pollination service provision. In this study, we assessed the relationship between stocking rates (honey bee hives and mason bee nesting material) and the abundance of honey bees and mason bees in 17 sweet cherry (Prunus avium) orchards in Central Germany. We furthermore performed a pollination experiment to explore the interactive effect of mason bees and honey bees on sweet cherry fruit set. In the orchards, both honey bee and mason bee abundance increased with increasing stocking rates of hives or nesting material, respectively. Honey bee abundance increased linearly with stocking rates. In contrast, mason bee abundance asymptoted at 2–3 nesting boxes per ha, beyond which more boxes resulted in little increase in visitation rate. Our pollination experiment demonstrated that orchards were pollen limited, with only 28% of insect‐pollinated flowers setting fruit versus 39% of optimally hand‐pollinated flowers. Honey bees and mason bees enhanced sweet cherry fruit set, but only when both were present and not when either was present alone in an orchard. Our findings demonstrate that offering nesting material for mason bees and employing honey bee hives can enhance bee abundance in sweet cherry orchards. By increasing honey bee abundance in combination with enhanced mason bee abundance, farmers can substantially boost fruit set and potentially sweet cherry yield. To enhance pollination services, farmers should consider the benefits of increasing pollinator biodiversity as an immediate benefit to improve crop yields.

Wild Floral Visitors Are More Important Than Honeybees as Pollinators of Avocado Crops

Wild insects provide pollination services in agroecosystems. Avocado is an economically important crop grown in the Chilean Mediterranean climate region and exported worldwide. Avocado pollination is managed using honeybee hives, while the role of wild insects as pollinators remains poorly known. We quantified the relative contributions of wild floral visitors and honeybees to the fruit set of avocados in two contrasting seasons (2015 and 2016) in Central Chile. Observations were made in 60 trees grown nearby (~300 m) to remnant patches of native sclerophyll vegetation. We found that honeybees and wild insects accounted for 48.6% and 51.4% of total floral visitation, respectively, with a 68% taxonomic similarity of floral visitors between seasons. The presence of honeybees significantly modulated the floral visitor composition and modified plant-pollination network parameters, which resulted in the biotic homogenization of the interaction network, through the increase of shared tree–floral visitor interactions, to the detriment of exclusive interactions. Finally, wild insects were more effective than honeybees in pollinating avocado trees and their contribution was greatest during the dry year. Thus, honeybees alone cannot be relied upon to deliver maximum pollination. We highlight ecological intensification practices to encourage wild insect visits and avoid native vegetation replacement with orchards. Therefore, we emphasize that future ecological intensification research should address agricultural practices to promote wild insects and evaluate the role of native vegetation as wild pollinator habitat in agricultural landscapes.

Exploring the effect of landscape composition and agroecological practices on wild bees in horticultural farms

How farms and the surrounding landscape are managed locally substantially affects biodiversity, with consequent impacts on the supply of certain ecosystem services, such as pollination. Wild bees provide pollination services for small-scale horticultural farming, and are key to determining and improving farm production, as well as maintaining ecosystem-level diversity. Here, we investigated how landscape composition and agroecological practices affect wild bee community in small-scale horticultural farms. The study was conducted at 16 horticultural farms in the northern part of Madrid. The pan-trapping method was used to collect wild bees during the flowering period of horticultural plants. We interviewed farmers to identify which agroecological practices were primarily adopted to attain a resilient ecosystem. The most common practices adopted were weed control methods, natural fertilizer usage, pest control, and crop diversification. In total, 109 wild bee species were identified, and included individuals from all six bee families present on the Iberian Peninsula. One genus (Lasioglossum) was highly abundant, accounting for 68% of individuals, and is a known ground nester. Areas of sparse vegetation and bare soil and forested areas primarily enhanced the richness of bee species. On the other hand, abundance of wild bees is enhanced by pasture and forest areas. The presence of these habitats in areas surrounding farms might represent the potential nesting sites with important resources for wild bees. Small-scale horticulture production promotes landscape diversity, which strongly promotes the potential of different ecosystem services, including pollination and wild bees. Thus, implementing agroecological practices could transcend farms, and individual fields, to the landscape level, providing long-term sustainability of ecosystems.

Floral richness and seasonality influences bee and non-bee flower interactions in urban community gardens

Pollinating insects are essential for food production. Both bee and non-bee pollinators are undergoing dramatic declines due to land use intensification and its consequences on native ecosystems. While interactions between crops and bee pollinators are well studied, our understanding of the pollination service provided by non-bee flower visitors including flies, ants, beetles and others is still limited. Moreover, the effects of landscape urbanization and changes in floral and nesting resource availability on the network structure of pollinators with both cultivated and wild plants have been poorly studied. We assessed which common bee and non-bee flower visitor groups dominate the interactions with both wild (e.g. Trifolium pratense, Taraxacum officinales) and cultivated plants (e.g. Fragaria ananassa, Cucurbita pepo) in urban community gardens in Berlin and Munich and explored how these interactions between flower visitor groups and plants change over the growing season. We further investigated the effect of changes in urbanization surrounding community gardens, and the availability of floral and nesting resources within gardens on the complexity (i.e. nestedness, linkage density, connectance) of interaction networks. We observed 20 focal plant species and 13 common bee and non-bee flower visitor groups in 30 urban community gardens. We found that dominant plant visitors changed over the growing season, with non-bee flower visitors including ants and flies as dominant early season visitors, and bee pollinators as important visitors later in the season. Nestedness of the flower visitor network increased with increases in floral richness in community gardens, while neither floral abundance nor the impervious surface surrounding the community gardens, garden size or the availability of nesting resources in gardens strongly influenced the flower visitor networks. Our findings suggest that high floral richness in community gardens may ensure the complexity and, thus, the stability of flower visitor networks. Findings further suggest that the role of non-bee flower visitors should be considered for pollination service provision especially in the shoulder seasons. Finally, our results emphasize that urban gardeners play a key role in mediating flower visitor interactions through their gardening practices.