Pollinators are responsible for the reproduction of many plant and crop species and provide important diversity for food webs and cultural value. Despite the critical ecosystem services provided by pollinators, rapid pollinator declines are occurring in response to anthropogenic activities that cause the loss of suitable habitat. There is an opportunity for urban green space to support pollination ecosystem services locally and across the landscape. However, there is a lack of practical but evidence-based guidance on how urban green space can be designed effectively to provide floral resources and other habitat needs to a diverse assemblage of pollinators. We examine the existing pollinator research in this paper to address the following questions specific to insect pollinators in temperate urban settings: (1) Which pollinators can be the focus of efforts to increase pollinator ecosystem services in cities? (2) Which plants and what arrangements of plants are most attractive and supportive to urban pollinators? (3) What do urban pollinators need beyond floral resources? (4) How can the surrounding landscape inform where to prioritize new habitat creation within cities? Using these questions as a framework, we provide specific and informed management and planning recommendations that optimize pollinator ecosystem value in urban settings.

Abstract Pollinators are declining globally, and this loss can reduce plant reproduction, erode critical ecosystem services and resilience, and drive economic losses. Monitoring pollinator biodiversity trends is essential for adaptive conservation and management, but conventional surveys are often costly, time‐consuming, and requires considerable taxonomic expertise. Environmental DNA (eDNA) metabarcoding surveys are booming due to their rapidity, nondestructiveness, and cost efficiency. Microfluidic technology allows multiple primer sets from different markers to be used in eDNA metabarcoding for more comprehensive inventories, minimizing associated primer bias. We evaluated microfluidic eDNA metabarcoding for pollinator community monitoring in both controlled greenhouse and natural field settings. Using a variety of sampling, preservation, and extraction methods, we assessed pollinator communities with a number of markers using microfluidic metabarcoding. In greenhouse experiments, microfluidic eDNA metabarcoding detected the target bumblebee in two of four focal flower species as well as greenhouse insects in all focal flower species. In the field, numerous common regional arthropods, including some directly observed, were detected. Pollinator detection was maximized using whole flower heads preserved in ATL buffer and extracted with a modified Qiagen® DNeasy protocol for amplification with COI primers. eDNA surveillance could enhance pollinator assessment by detecting protected and endangered species and being more applicable to remote, inaccessible locations, whilst reducing survey time, effort, and expense. Microfluidic eDNA metabarcoding requires optimization to address remaining efficacy concerns, but this approach shows potential in revealing complex networks underpinning critical ecosystem functions and services, enabling more accurate assessments of ecosystem resilience.

International audience | Recent insect pollinator declines, mainly due to the expansion and intensification of agricultural land use, are jeopardizing ecosystem service provisioning in agroecosystems. Organic farming has been suggested as a biodiversity-friendly alternative to conventional farming, but additional insights evaluating its effectiveness in perennial cropping systems are needed. Here, we provide a comprehensive analysis of local and landscape effects on the provided pollination services and yield in apple crops. We first used mixed models to disentangle effects of agricultural management and landscape effects on both taxonomic and functional diversity of wild bees and hoverflies during bloom in both organic and integrated pest management (IPM) apple orchards in Belgium, and then compared these biodiversity indicators with semi-natural grasslands as a benchmark. Next, we applied piecewise structural equation modeling to quantify the direct and indirect effects of orchard management type and landscape on fruit set, seed set and ultimately on crop yield. Orchards, regardless of their type of management, hosted lower taxonomic and functional pollinator diversity compared to the semi-natural benchmark. Yet, pollinator abundance and diversity were higher in orchard edges and increased with small-scale landscape diversity, which was positively associated with the presence of semi-natural habitat, as well as arable and urban land. Investigating the cascading effects on apple yield, we found that yield levels were not shaped by the observed pollinator diversity or by the measured pollination services, but were lower in organic orchards. Overall, we conclude that apple yield was likely not pollinator limited in our study system, but that conserving and restoring semi-natural habitats, maintaining and expanding orchard edges through reducing field sizes and promoting landscape diversity are the most promising avenues for pollinator conservation in orchard landscapes.

Bees provide a critical ecosystem service for agricultural production by contributing to the pollination of the majority of leading global crops. A growing body of research indicates that species rich pollinator communities benefit the yields and stability of insect-pollinated crops. Additionally, species rich communities may promote more resilient crop pollination services, which is particularly imperative due to increasing rates of anthropogenic induced environmental changes. However, this ecosystem service is being compromised due to declines in bee species, driven by a loss of floral and nesting resources due to agricultural land expansion and intensification. Whilst agri-environment schemes have been implemented across Europe to halt biodiversity losses, recent evidence suggests that they predominantly benefit common bumblebee species, and are of limited value to solitary species, which also provide important crop pollination services. Currently there is limited information on which species provide crop pollination services to guide management and monitoring, and preserve pollination services. Identifying crop pollinating bee species, monitoring their populations in agricultural landscapes and understanding how crop pollinator communities vary across time and space have recently been identified as key research objectives for national and international policy and monitoring programmes. Focusing on Great Britain, which has comprehensive data on its bee fauna, and considering four of its most economically important crops – apples, field bean, oilseed rape and strawberries – this thesis aimed to address key knowledge gaps in our understanding of bee crop pollinator communities. The first objective of this thesis was to produce national lists of bee pollinators for each of the four focal crops. Building upon this information the second objective was to evaluate the capacity of different survey methods to sample bee species in each of these crops. The final objective was to investigate how pollinator community composition, and pollinator species richness, may affect the stability of crop pollinator occurrence. The results of chapter 2 indicate that whilst a smallsuite of common species may make a disproportionate contribution to flower visitation to our focal crops, at least a quarter of bee species in Great Britain, including some rare and specialist ones, could act as potential pollinators of these crops. These findings indicate that current agri-environment schemes, which have been predominantly developed around the needs of bumblebees, may not be as effective at supporting pollination service in crops such as apples and oilseed, which are also visted by a diverse range of solitary bees. Chapter 3 revealed that different survey methods sample distinct components of crop pollinator communities, and that the efficacy of different survey methods to sample bee crop pollinators may be contingent upon the guild and crop being targeted. Transect walks were superior at measuring both abundance and richness of bumblebees in all crops, and may be sufficient to sample bee pollinators in crops such as field bean, which are almost exclusively visited by bumblebees. Pan traps, notably yellow ones, detected the greatest abundance and species richness of solitary bees in apple, oilseed and strawberry crop sites, and may be an essential complementary sampling technique in crops for which solitary bees are key pollinators. These findings can be used to inform national pollinator monitoring schemes which aim to sample crop pollinators in agricultural areas. Finally, the results of chapter 4 indicate that bee crop pollinator communities composed of a small number of closely related species, such as field bean, are likely to exhibit more synchronized inter-annual occupancy dynamics, and show a greater variance in mean occupancy, compared to crop pollinator communities comprised of a more diverse set of bee species, such as oilseed. Additional analyses also indicate that more species rich pollinator communities may result in greater stability of crop pollinator occurrence over time, which could have positive benefits for the resilience of crop pollination services under future environmental changes. The outcomes of this thesis show that agri-environment schemes need to be adapted to cater for the resource requirements of a wider diversity of bee species than at present, and strategies to achieve this are discussed within the context of the wider literature. The implications of differences in the capacity of different survey methods to sample and monitor crop pollinating bee species are also discussed. Additionally, a consideration of how management in agricultural landscapes can promote stable bee populations in and around cropped areasis also provided. Together these recommendations provide an overview of how species-rich and stable bee crop pollinator populations could be protected and promoted in agricultural landscapes in order to safeguard production of insect pollinated crops.

Wildflower strips are increasingly promoted in pollinator conservation schemes to maintain the stability of ecosystem services and increase crop yield. Yet, the increased area of avocado Persea americana Mill. cultivation in sub-Saharan Africa is not accompanied by measures of biodiversity conservation or the promotion of ecosystem services. We investigated the effects of flower strips on flower visitors and avocado fruit set in Kenya. A strip mixture of sunflower Helianthus annuus L., coriander Coriandrum sativum L., and alfalfa Medicago sativa L. was established at the border of four avocado plots, while four other plots with an unmanaged border served as control. The abundance of insect flower visitors and fruit set at 10 m, 55 m, and 100 m from the border of each plot were assessed during the early, peak, and late avocado flowering periods. The honeybee Apis mellifera L. and hoverflies Syrphidae spp. accounted for 22% and 71% of flower visitors, respectively. We found interactions between the treatment, distance to the border, and the avocado flowering intensity on the abundance of honeybees but not on hoverflies. Irrespective of the distance to the border and the avocado’s flowering intensity, flower strips acted as a sink for honeybees and hoverflies. Overall, the flower strip mixture of sunflower, coriander, and alfalfa did not increase pollinator abundance and avocado productivity, and it may be necessary to identify plant species for optimal benefits and study the long-term effects of floral strips on pollinators and crop production.

BackgroundHomegardens in agricultural areas are important refuges for pollinators and other valuable species due to the extensive plant diversity therein. Yet, plant diversity may strongly depend on the identity of the gardeners and their knowledge of plant identification and plant uses.ObjectiveIn this study, we used botanical surveys and homegardener interviews to explore plant diversity in homegardens in coffee-producing regions of Colombia, and to examine how homegardener identity influences their knowledge of plants, plant uses, and motivations for maintaining a homegarden.MethodsWe collected information in three villages in Cauca, Colombia and interviewed campesino (n = 30) and indigenous (n = 30) homegardeners. Half of the respondents from each social group were women and half were men.Results and discussionOf the 566 plant species that we detected in botanical surveys, the most recognized spontaneous herbs among homegardeners were “papunga” (Bidens pilosa, n = 38), “lechuguilla” (Emilia sonchifolia, n = 32), and “escoba” (Sida acuta, n = 31). Homegardeners identified multiple uses of spontaneous herbs including for food, material, medicine, plants for bees, and other environmental, conservation, or social uses. In addition, three different groups of gardeners emerged from social groupings and interview responses: (1) indigenous men with little knowledge of the uses of spontaneous herbs; (2) indigenous and campesino women who considered it beneficial to have flowers and crops for pollinators; and (3) male farmers who described detailed mutualistic plant-pollinator interactions that benefit crops, and who use spontaneous herbs to maintain soil moisture. In conclusion, homegardeners kept very diverse gardens and identified spontaneous herbs and pollinator functions, but this strongly depended on age, knowledge, and social group. Thus, homegarden presence within agricultural landscapes is of great importance to sustain functional biodiversity and ecosystem services in Colombian agroecosystems.ConclusionIn conclusion, homegardeners kept very diverse gardens and identified spontaneous herbs and pollinator functions, but this strongly depended on age, knowledge, and social group. Thus, homegarden presence within agricultural landscapes is of great importance to sustain functional biodiversity and ecosystem services in Colombian agroecosystems.

Pollination is a fundamental ecosystem service. Predictive and mechanistic models linking pollinator community structure to pollination services increasingly incorporate information on unique functional differences among species, so called effects traits.   There is little consensus as to which traits are most important in supporting pollination services at either an individual or community level. Here, we synthesise the state of current knowledge regarding the role and efficacy of traits for predicting pollination, as well as the use of different methods for describing the trait structure of pollinator assemblages. We find a wide range of traits are currently used to predict pollination services, including morphological, behavioural and phenological characteristics. However, we show that the evidence demonstrating their importance is often limited or mixed. There is a trade-off in how traits are used between those that are easier to measure, available for many species but have only limited evidence for their role in pollination, vs. those that are harder to measure but with a more robust link with pollination service delivery.   We highlight how community weighted means and measures of functional diversity offer important, albeit different insights into pollination service delivery. We discuss how their relative importance is likely to depend on the goals of the study. To maximise fully the utilisation of traits to predict pollination services, future research should be directed towards the widespread and consistent validation of the links among different traits and the pollination service across crop and semi-natural plant communities. Ideally this also needs to address geographical and taxonomic biases in trait collection.

Pollinators provide crucial ecosystem services, i.e., pollination, which determines crops’ reproductive fitness and yield. As pollinators decline, flowering crops might face pollination-deficit stress depending on their dependence on pollinators and pollinator availability. Here, we assessed the dependency of some crops (belonging to diverse plant families) on biotic pollinators based on their maximum reproductive potential in a supplementary pollination treatment and minimum reproductive success in a pollinator exclusion treatment. Additionally, we determined the pollen transfer limitation of the crops in open field conditions. We also determined the influence of the different reproductive traits with the index of dependency of crops on pollinators (<i>IDP</i>) and the coefficient of pollination deficit (<i>D</i>). Based on the values of <i>IDP</i>, members of Cucurbitaceae are obligatorily dependent on pollinators for their fruit set. Members of Brassicaceae and Rutaceae are highly reliant on pollinators. A few crops, like <i>Lablab purpureus</i> and <i>Nigella sativa</i>, are less dependent on pollinators. In open field conditions, most crops have a low pollination deficit, some without pollen transfer limitations, and only a few crops (<i>Citrus × limon</i> and <i>Citrus maxima</i>) show a higher pollination deficit. The <i>IDP</i> is negatively influenced by the pollen–ovule ratio, which also negatively affects the pollination deficit of the crops. This study will be useful in understanding and mitigating the effects of pollinator losses, as well as in choosing crops (those under pollination deficit stress and largely dependent on pollinators for fruit set) for supplemental pollination services to increase agricultural production.

Restoration of native tropical forests is crucial for protecting biodiversity and ecosystem functions, such as carbon stock capacity. However, little is known about the contribution of early stages of forest regeneration to crop productivity through the enhancement of ecosystem services, such as crop pollination and pest control. Using data from 610 municipalities along the Brazilian Atlantic Forest (30 m spatial resolution), we evaluated if young regenerating forests (YRFs) (less than 20 years old) are positively associated with coffee yield and whether such a relationship depends on the amount of preserved forest in the surroundings of the coffee fields. We found that regenerating forest alone was not associated with variations in coffee yields. However, the presence of YRF (within a 500 m buffer) was positively related to higher coffee yields when the amount of preserved forest in a 2 km buffer is above a 20% threshold cover. These results further reinforce that regional coffee yields are influenced by changes in biodiversity-mediated ecosystem services, which are explained by the amount of mature forest in the surrounding of coffee fields. We argue that while regenerating fragments may contribute to increased connectivity between remnants of forest fragments and crop fields in landscapes with a minimum amount of forest (20%), older preserved forests (more than 20 years) are essential for sustaining pollinator and pest enemy's populations. These results highlight the potential time lag of at least 20 years of regenerating forests' in contributing to the provision of ecosystem services that affect coffee yields (e.g. pollination and pest control). We emphasize the need to implement public policies that promote ecosystem restoration and ensure the permanence of these new forests over time. | info:eu-repo/semantics/publishedVersion

ABSTRACT Pollination services provided by wild insect pollinators are critical to natural ecosystems and crops around the world. There is an increasing appreciation that the gut microbiota of these insects influences their health and consequently their services. However, pollinator gut microbiota studies have focused on well-described social bees, but rarely include other, more phylogenetically divergent insect pollinators. To expand our understanding, we explored the insect pollinator microbiomes across three insect orders through two DNA sequencing approaches. First, in an exploratory 16S amplicon sequencing analysis of taxonomic community assemblages, we found lineage-specific divergences of dominant microbial genera and microbiota community composition across divergent insect pollinator genera. However, we found no evidence for a strong broad-scale phylogenetic signal, which we see for community relatedness at finer scales. Subsequently, we utilized metagenomic shotgun sequencing to obtain metagenome-assembled genomes and assess the functionality of the microbiota from pollinating flies and social wasps. We uncover a novel gut microbe from pollinating flies in the family Orbaceae that is closely related to Gilliamella spp. from social bees but with divergent functions. We propose this novel species be named Candidatus Gilliamella eristali. Further metagenomes of dominant fly and wasp microbiome members suggest that they are largely not host-insect adapted and instead may be environmentally derived. Overall, this study suggests selective processes involving ecology or physiology, or neutral processes determining microbe colonization may predominate in the turnover of lineages in insect pollinators broadly, while evolution with hosts may occur only under certain circumstances and on smaller phylogenetic scales. IMPORTANCE Wild insect pollinators provide many key ecosystem services, and the microbes associated with these insect pollinators may influence their health. Therefore, understanding the diversity in microbiota structure and function, along with the potential mechanisms shaping the microbiota across diverse insect pollinators, is critical. Our study expands beyond existing knowledge of well-studied social bees, like honey bees, including members from other bee, wasp, butterfly, and fly pollinators. We infer ecological and evolutionary factors that may influence microbiome structure across diverse insect pollinator hosts and the functions that microbiota members may play. We highlight significant differentiation of microbiomes among diverse pollinators. Closer analysis suggests that dominant members may show varying levels of host association and functions, even in a comparison of closely related microbes found in bees and flies. This work suggests varied importance of ecological, physiological, and non-evolutionary filters in determining structure and function across largely divergent wild insect pollinator microbiomes.