A Distinct Arabidopsis Latent Virus 1 Isolate Was Found in Wild Brassica hirta Plants and Bees, Suggesting the Potential Involvement of Pollinators in Virus Spread.

During our search for aphid-pathogenic viruses, a comovirus was isolated from wild asymptomatic Brassica hirta (white mustard) plants harboring a dense population of Brevicoryne brassicae aphids. The transmission-electron-microscopy visualization of purified virions revealed icosahedral particles. The virus was mechanically transmitted to plants belonging to Brassicaceae, Solanaceae, Amaranthaceae, and Fabaceae families, showing unique ringspot symptoms only on B. rapa var. perviridis plants. The complete viral genome, comprised of two RNA segments, was sequenced. RNA1 and RNA2 contained 5921 and 3457 nucleotides, respectively, excluding the 3' terminal poly-adenylated tails. RNA1 and RNA2 each had one open-reading frame encoding a polyprotein of 1850 and 1050 amino acids, respectively. The deduced amino acids at the Pro-Pol region, delineated between a conserved CG motif of 3C-like proteinase and a GDD motif of RNA-dependent RNA polymerase, shared a 96.5% and 90% identity with the newly identified Apis mellifera-associated comovirus and Arabidopsis latent virus 1 (ArLV1), respectively. Because ArLV1 was identified early in 2018, the B. hirta comovirus was designated as ArLV1-IL-Bh. A high-throughput-sequencing-analyses of the extracted RNA from managed honeybees and three abundant wild bee genera, mining bees, long-horned bees, and masked bees, sampled while co-foraging in a Mediterranean ecosystem, allowed the assembly of ArLV1-IL-Bh, suggesting pollinators' involvement in comovirus spread in weeds.

Complex Effects of a Land-Use Gradient on Pollinators and Natural Enemies: Natural Habitats Mitigate the Effects of Aphid Infestation on Pollination Services.

Pollinators and natural enemies are essential ecosystem service providers influenced by land-use and by interactions between them. However, the understanding of the combined impacts of these factors on pollinator and natural enemy activities and their ultimate effects on plant productivity remains limited. We investigated the effects of local and landscape vegetation characteristics and the presence of herbivorous pests on pollination and biological control services and their combined influence on phytometer seed set. The study was conducted in a Mediterranean agro-ecosystem, encompassing ten shrubland plots spanning a land-use gradient. Within each plot, we placed caged and uncaged potted phytometer plants that were either aphid-infested or aphid-free. We quantified insect flower visitation, aphid predation and parasitism rates, and fruit and seed set. We found scale-dependent responses of pollinators and natural enemies to land-use characteristics. Flower species richness had a positive impact on aphid parasitism rates but a negative effect on pollinator activity. Notably, we found a more pronounced positive effect of natural areas on pollinator activity in aphid-infested compared to aphid-free plants, indicating a potentially critical role of natural habitats in mitigating the adverse effects of aphid infestation on pollination services. These results highlight the complex and interactive effects of land-use on pollinators and natural enemies, with significant implications for plant productivity.

Characterization Factors to Assess Land Use Impacts on Pollinator Abundance in Life Cycle Assessment.

While wild pollinators play a key role in global food production, their assessment is currently missing from the most commonly used environmental impact assessment method, Life Cycle Assessment (LCA). This is mainly due to constraints in data availability and compatibility with LCA inventories. To target this gap, relative pollinator abundance estimates were obtained with the use of a Delphi assessment, during which 25 experts, covering 16 nationalities and 45 countries of expertise, provided scores for low, typical, and high expected abundance associated with 24 land use categories. Based on these estimates, this study presents a set of globally generic characterization factors (CFs) that allows translating land use into relative impacts to wild pollinator abundance. The associated uncertainty of the CFs is presented along with an illustrative case to demonstrate the applicability in LCA studies. The CFs based on estimates that reached consensus during the Delphi assessment are recommended as readily applicable and allow key differences among land use types to be distinguished. The resulting CFs are proposed as the first step for incorporating pollinator impacts in LCA studies, exemplifying the use of expert elicitation methods as a useful tool to fill data gaps that constrain the characterization of key environmental impacts.

Metatranscriptome Analysis of Sympatric Bee Species Identifies Bee Virus Variants and a New Virus, Andrena-Associated Bee Virus-1.

Bees are important plant pollinators in agricultural and natural ecosystems. High average annual losses of honey bee (Apis mellifera) colonies in some parts of the world, and regional population declines of some mining bee species (Andrena spp.), are attributed to multiple factors including habitat loss, lack of quality forage, insecticide exposure, and pathogens, including viruses. While research has primarily focused on viruses in honey bees, many of these viruses have a broad host range. It is therefore important to apply a community level approach in studying the epidemiology of bee viruses. We utilized high-throughput sequencing to evaluate viral diversity and viral sharing in sympatric, co-foraging bees in the context of habitat type. Variants of four common viruses (i.e., black queen cell virus, deformed wing virus, Lake Sinai virus 2, and Lake Sinai virus NE) were identified in honey bee and mining bee samples, and the high degree of nucleotide identity in the virus consensus sequences obtained from both taxa indicates virus sharing. We discovered a unique bipartite + ssRNA Tombo-like virus, Andrena-associated bee virus-1 (AnBV-1). AnBV-1 infects mining bees, honey bees, and primary honey bee pupal cells maintained in culture. AnBV-1 prevalence and abundance was greater in mining bees than in honey bees. Statistical modeling that examined the roles of ecological factors, including floral diversity and abundance, indicated that AnBV-1 infection prevalence in honey bees was greater in habitats with low floral diversity and abundance, and that interspecific virus transmission is strongly modulated by the floral community in the habitat. These results suggest that land management strategies that aim to enhance floral diversity and abundance may reduce AnBV-1 spread between co-foraging bees.

Wild insect diversity increases inter-annual stability in global crop pollinator communities.

While an increasing number of studies indicate that the range, diversity and abundance of many wild pollinators has declined, the global area of pollinator-dependent crops has significantly increased over the last few decades. Crop pollination studies to date have mainly focused on either identifying different guilds pollinating various crops, or on factors driving spatial changes and turnover observed in these communities. The mechanisms driving temporal stability for ecosystem functioning and services, however, remain poorly understood. Our study quantifies temporal variability observed in crop pollinators in 21 different crops across multiple years at a global scale. Using data from 43 studies from six continents, we show that (i) higher pollinator diversity confers greater inter-annual stability in pollinator communities, (ii) temporal variation observed in pollinator abundance is primarily driven by the three-most dominant species, and (iii) crops in tropical regions demonstrate higher inter-annual variability in pollinator species richness than crops in temperate regions. We highlight the importance of recognizing wild pollinator diversity in agricultural landscapes to stabilize pollinator persistence across years to protect both biodiversity and crop pollination services. Short-term agricultural management practices aimed at dominant species for stabilizing pollination services need to be considered alongside longer term conservation goals focussed on maintaining and facilitating biodiversity to confer ecological stability.

A critical analysis of the potential for EU Common Agricultural Policy measures to support wild pollinators on farmland.

Agricultural intensification and associated loss of high-quality habitats are key drivers of insect pollinator declines. With the aim of decreasing the environmental impact of agriculture, the 2014 EU Common Agricultural Policy (CAP) defined a set of habitat and landscape features (Ecological Focus Areas: EFAs) farmers could select from as a requirement to receive basic farm payments. To inform the post-2020 CAP, we performed a European-scale evaluation to determine how different EFA options vary in their potential to support insect pollinators under standard and pollinator-friendly management, as well as the extent of farmer uptake.A structured Delphi elicitation process engaged 22 experts from 18 European countries to evaluate EFAs options. By considering life cycle requirements of key pollinating taxa (i.e. bumble bees, solitary bees and hoverflies), each option was evaluated for its potential to provide forage, bee nesting sites and hoverfly larval resources.EFA options varied substantially in the resources they were perceived to provide and their effectiveness varied geographically and temporally. For example, field margins provide relatively good forage throughout the season in Southern and Eastern Europe but lacked early-season forage in Northern and Western Europe. Under standard management, no single EFA option achieved high scores across resource categories and a scarcity of late season forage was perceived.Experts identified substantial opportunities to improve habitat quality by adopting pollinator-friendly management. Improving management alone was, however, unlikely to ensure that all pollinator resource requirements were met. Our analyses suggest that a combination of poor management, differences in the inherent pollinator habitat quality and uptake bias towards catch crops and nitrogen-fixing crops severely limit the potential of EFAs to support pollinators in European agricultural landscapes. Policy Implications. To conserve pollinators and help protect pollination services, our expert elicitation highlights the need to create a variety of interconnected, well-managed habitats that complement each other in the resources they offer. To achieve this the Common Agricultural Policy post-2020 should take a holistic view to implementation that integrates the different delivery vehicles aimed at protecting biodiversity (e.g. enhanced conditionality, eco-schemes and agri-environment and climate measures). To improve habitat quality we recommend an effective monitoring framework with target-orientated indicators and to facilitate the spatial targeting of options collaboration between land managers should be incentivised.

La intensificación agrícola y la consecuente pérdida de hábitats de alta calidad son desencadenantes clave del declive de los insectos polinizadores. Con el objetivo de disminuir el impacto ambiental de la agricultura, la Política Agrícola Común (PAC) de la UE de 2014 definió un conjunto de medidas para hábitats y paisajes (Áreas de Enfoque Ecológico: EFA por sus siglas en inglés) que los agricultores podían seleccionar como requisito para recibir pagos agrícolas básicos. Para informar la reforma de la PAC a partir a 2020, realizamos una evaluación a escala europea para determinar cómo las diferentes opciones de EFA varían en su potencial para asistir a los insectos polinizadores bajo un manejo estándar y amigable con los polinizadores, así como su aceptación por parte de los agricultores.El proceso estructurado de elicitación Delphi para evaluar las opciones de EFA involucró a 22 expertos de 18 países europeos. Se consideraron los requisitos de los diferentes taxones de polinizadores (es decir, abejorros, abejas solitarias y sírfidos) evaluando cada opción por su potencial para proporcionar forraje, sitios de nidificación y recursos para las larvas.Las opciones de EFA variaron sustancialmente en la cantidad de recursos que se percibía que proporcionan y su efectividad vario geográfica y temporalmente. Por ejemplo, los márgenes de cultivos proporcionan un forraje relativamente bueno durante toda la temporada en el sur y el este de Europa, pero carecen de forraje a principios de temporada en el norte y oeste de Europa. Bajo el manejo estándar, ninguna opción de EFA logró puntuaciones altas en todas las categorías de recursos y en general se percibió una escasez de forraje al final de la temporada.Los expertos identificaron oportunidades sustanciales para mejorar la calidad del hábitat mediante la adopción de un manejo amigable con los polinizadores. Sin embargo, mejorar la gestión por sí solo es poco probable que garantice que se cumplan todos los requisitos necesarios para los polinizadores. Nuestro análisis sugiere que una combinación de manejo inadecuado, diferencias de calidad inherentes a los distintos hábitat y el sesgo de aceptación hacia cultivos de cobertura y cultivos que fijan nitrógeno limitan severamente el potencial de los EFA para apoyar a los polinizadores en los paisajes agrícolas europeos. Implicaciones políticas. Para conservar a los polinizadores y ayudar a proteger los servicios de polinización, nuestro estudio destaca la necesidad de crear una variedad de hábitats interconectados y bien administrados que se complementen entre sí en los recursos que ofrecen. Para lograr esto, la PAC post­2020 debe integrar los diferentes vehículos de implementación destinados a proteger la biodiversidad (por ejemplo, condicionalidad mejorada, esquemas ecológicos y medidas agroambientales y climáticas). Para mejorar la calidad del hábitat, recomendamos un marco de monitoreo efectivo con indicadores orientados a objetivos y incentivar la colaboración entre los administradores de las tierras.

L'intensification agricole et la perte associée d'habitats semi­naturels sont les principaux moteurs du déclin des insectes pollinisateurs. Dans l'intention de réduire l'impact environnemental de l'agriculture, la politique agricole commune (PAC) de l'UE de 2014 a défini un ensemble d'habitats et d'éléments paysagers (surfaces d'intérêt écologique: SIE) dans la mise en place ou le respect desquels les agriculteurs pouvaient s'engager comme condition pour bénéficier d'aides économiques européennes (droit au paiement de base). Pour éclairer la PAC post­2020, nous avons évalué à l'échelle européenne et à dire d'expert, d'une part les potentialités des diverses SIE à favoriser les insectes pollinisateurs, via une gestion standard et via une gestion optimisée, et d'autre part l'étendue de l'adoption de ces mesures par les agriculteurs.Un processus structuré d'élaboration et d'agrégation des opinions (méthode Delphi) a fait appel à 22 experts de 18 pays européens pour évaluer les potentialités des diverses SIE. Considérant les traits bioécologiques des principaux taxons pollinisateurs (i.e. bourdons, abeilles solitaires et syrphes), chaque SIE a été évaluée pour son potentiel à fournir des ressources trophiques et des sites de reproduction (sites de nidification pour les bourdons et abeilles, sites de ponte et développement larvaire pour les syrphes).Les SIE différaient considérablement les unes des autres sur les ressources qu'elles étaient censées offrir et leur efficacité variait géographiquement et temporellement. Par exemple, les bords de champ peuvent fournir des ressources trophiques tout au long de l'année en Europe du Sud et de l'Est mais pas en début de saison en Europe du Nord et de l'Ouest. En cas de gestion standard, aucun type de SIE n'atteint de score élevé pour aucun type de ressource, et une période de disette alimentaire survient en fin de saison.Les experts ont mis en évidence de possibles et substantielles améliorations des SIE par le biais de leur gestion optimisée. Cependant, cette seule amélioration ne garantit pas la fourniture de ressources suffisantes aux pollinisateurs des paysages agricoles européens. Pour cela, des habitats spécifiques doivent être favorisés, dont la mise en place ne doit pas être entravée par un choix massif de SIE à base de cultures intermédiaires pièges à nitrates ou fixatrices d'azote. Implications politiques. Pour préserver les pollinisateurs et le service de pollinisation des plantes entomophiles, notre étude souligne la nécessité de créer une diversité d'habitats interconnectés, gérés de façon optimale, qui se complètent mutuellement dans les ressources qu'ils offrent. Pour atteindre cet objectif, la PAC post­2020 doit adopter une vision holistique de la mise en œuvre des différents leviers de protection de la biodiversité (e.g. éco­conditionnalité renforcée, programmes verts ou 'eco­schemes', mesures agro­environnementales et climatiques). Pour réellement améliorer la qualité des habitats, nous recommandons des suivis efficaces de la biodiversité à l'aide d'indicateurs pertinents. Enfin, pour optimiser la disposition spatiale des SIE et leur connectivité, la collaboration entre les différents gestionnaires des espaces agricoles doit être encouragée.

A intensificação agrícola e a perda associada de habitats de elevada qualidade são os principais factores que impulsionam o declínio dos insetos polinizadores. A fim de mitigar o impacto ambiental da agricultura, a Política Agrícola Comum (PAC) da UE, de 2014, definiu um conjunto de atributos ou estruturas do habitat e da paisagem, designadas de Áreas Foco Ecológico (AFEs) que devem ser mantidas pelos agricultores como requisito para obter as ajudas económicas previstas nas medidas agroambientais. No presente trabalho realizamos uma avaliação à escala europeia das diferentes opções destas estruturas, a fim de munir a PAC pós­2020, com informação sobre a importância das AFEs. Estas variam muito quanto ao seu potencial no apoio às populações de polinizadores, de acordo com a extensão da sua aceitação pelos agricultores e das práticas adoptadas por estes na sua gestão, que podem consistir em práticas padrão ou práticas mais amigáveis para os polinizadores.Um processo estruturado, com base na técnica de elicitação de Delphi foi desenvolvido, envolvendo 22 especialistas de 18 países europeus, com o objectivo de avaliar as opções de AFEs previstas na PAC. Esta avaliação levou em consideração os requisitos do ciclo de vida dos taxa dos principais polinizadores, ou seja, as abelhas, as abelhas solitárias e os sirfídeos ou moscas­das­flores. Cada AFE foi avaliada quanto ao seu potencial para fornecer alimento, locais de nidificação, e recursos para as larvas dos sirfídeos.A percepção quanto à eficácia das AFEs como fonte de recursos (alimento) para os polinizadores variou substancialmente, do ponto de vista quer geográfico, quer temporal (época do ano). Por exemplo, a AFE, faixas verdes nas margens do campo são consideradas uma boa fonte de alimento, no sul e leste da Europa, durante todo ano, mas ineficazes, no norte e oeste da Europa, no início do ano. Nenhuma EFA alcançou pontuações elevadas na categoria de recursos (fonte de alimento), quando submetida ao maneio padrão, sendo consideradas ineficientes, na segunda metade do ano.Os especialistas envolvidos identificaram oportunidades de melhoria substancial na qualidade do habitat, através da adopção de práticas de maneio das EFAs mais "amigáveis" para com os polinizadores. No entanto, a melhoria das práticas de maneio das EFAs por si só, dificilmente garantirá todos os requisitos necessários para a manutenção das populações de polinizadores. A nossa avaliação sugere que a combinação de práticas de má gestão (maneio), diferenças inerentes à qualidade do habitat dos polinizadores e o aumento do bias que resulta da utilização de espécies de crescimento rápido ou fixadoras de azoto limitam severamente o papel e potencial destas estruturas na manutenção das populações de polinizadores nas paisagens agrícolas europeias. Implicações políticas. A conservação dos polinizadores ajuda a proteger os serviços de polinização providenciados por estes. O nosso estudo destaca a necessidade de criar uma variedade de habitats interconectados e geridos de forma que se complementem na oferta de recursos (alimento, locais de nidificação e recursos para as larvas) aos polinizadores. Para atingir este objectivo, a PAC pós­2020 deve adoptar uma visão holística na implementação das EFAs, que integre os diferentes programas destinados a protecção da biodiversidade (por exemplo, maior condicionalidade, esquemas ecológicos, e medidas agroambientais e de adaptação climática). Para melhorar a qualidade do habitat, recomendamos uma estrutura de monitorização eficaz suportada por indicadores quantitativos e qualitativos orientados para metas, que permitam facilitar a tomada de decisões direcionadas especificamente para as EFAs, e que a colaboração entre os gestores da terra (agricultores) seja incentivada.

Rangeland sharing by cattle and bees: moderate grazing does not impair bee communities and resource availability.

Rangelands are a dominant anthropogenic land use and a main driver of natural habitat loss worldwide. Land sharing, the integration of agricultural production and biodiversity conservation, may provide a platform for managing rangelands to fulfill multiple ecosystem services. However, livestock grazing can greatly affect biodiversity and little is known about its effects on providers of focal ecosystem services, such as pollinators. We investigated the effect of cattle grazing on bee communities and their foraging and nesting resources in Mediterranean rangelands. Specifically, we explored the effect of moderate cattle grazing on flowering plant abundance, species richness and composition, the diversity of nesting substrates, and consequently, the possible effects on wild bee and honey bee foraging activity, species diversity, and community composition. We conducted field research in the Mediterranean rangelands of Israel during the main bee activity season, in the spring of 2012 and 2013, comparing paired cattle-grazed and ungrazed areas. The availability of floral and nesting resources for bees was unaffected or positively affected by grazing. Similarly, wild bee abundance, species richness, and composition were not affected by grazing, but were instead shaped by spatiotemporal factors. Nor was honey bee activity level impaired by grazing. The foraging preferences of bees, as well as flower species composition and peak bloom differed between grazed and ungrazed areas. Therefore, in our studied rangelands, grazing had its main effect on the foraging choices of honey bees and wild bees, rather than on their abundance and diversity. Moreover, our results indicate the potentially important role of ungrazed patches in increasing nectar and pollen diversity and availability in rangelands for both honey bees and wild bees in the spring. Hence, maintaining a mosaic of moderately grazed and ungrazed patches is expected to provide the greatest benefits for wild bee conservation and honey bee activity in Mediterranean rangelands. Our findings support the notion of rangeland sharing by cattle and bees in Mediterranean ecosystems under moderate grazing intensities, mimicking the coexistence of honey bees, wild bees, and cattle in Mediterranean ecosystems on an evolutionary timescale.

Priority Questions and Horizon Scanning for Conservation: A Comparative Study.

Several projects aimed at identifying priority issues for conservation with high relevance to policy have recently been completed in several countries. Two major types of projects have been undertaken, aimed at identifying (i) policy-relevant questions most imperative to conservation and (ii) horizon scanning topics, defined as emerging issues that are expected to have substantial implications for biodiversity conservation and policy in the future. Here, we provide the first overview of the outcomes of biodiversity and conservation-oriented projects recently completed around the world using this framework. We also include the results of the first questions and horizon scanning project completed for a Mediterranean country. Overall, the outcomes of the different projects undertaken (at the global scale, in the UK, US, Canada, Switzerland and in Israel) were strongly correlated in terms of the proportion of questions and/or horizon scanning topics selected when comparing different topic areas. However, some major differences were found across regions. There was large variation among regions in the percentage of proactive (i.e. action and response oriented) versus descriptive (non-response oriented) priority questions and in the emphasis given to socio-political issues. Substantial differences were also found when comparing outcomes of priority questions versus horizon scanning projects undertaken for the same region. For example, issues related to climate change, human demography and marine ecosystems received higher priority as horizon scanning topics, while ecosystem services were more emphasized as current priority questions. We suggest that future initiatives aimed at identifying priority conservation questions and horizon scanning topics should allow simultaneous identification of both current and future priority issues, as presented here for the first time. We propose that further emphasis on social-political issues should be explicitly integrated into future related projects.

Non-bee insects are important contributors to global crop pollination.

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.

Reliability and refinement of the higher taxa approach for bee richness and composition assessments.

Limited resources and taxonomic expertise in biodiversity surveys often lead to the application of the higher taxa approach (HTA),i.e., the identification of specimens to genus or higher taxonomic levels rather than to species. The reliability of the HTA varies significantly among studies, yet the factors underlying this variability have rarely been investigated. Bees are an ideal model taxon for testing the HTA because they are highly diverse, challenging to identify, and there is widespread interest in their role as native pollinators, driving demand for efficient diversity assessment tools. Using extensive bee data sets collected across three biomes and various habitats, we assessed the performance of the HTA in reflecting bee species richness and composition patterns at local scales, factors affecting this performance, and ways to improve it. The performance of the HTA varied considerably among biomes, taxonomic levels (genera and subfamilies), and diversity measures (species richness and composition); genus and subfamily richness accounted for 55-77% and 32-61% of the variation in species richness, respectively; genus and subfamily composition accounted for 28-87% and 26-80% of the variation in species composition, respectively. The number of species per higher taxon was a main factor influencing this performance (accounting for 63% of the variation), while the co-occurrence of taxonomically related species had no significant influence on the performance of the HTA. Further subdividing genera by body size contributed to the performance of the HTA and increased its accuracy in representation of compositional patterns by ~16%. Our results have several practical implications. The considerable variability found in the performance of the HTA in representing local-scale richness and composition patterns of bee species dictates caution in implementing this tool in bee surveys. When possible, an a priori evaluation of the expected performance of the HTA should be done, focusing on species distributions within higher taxonomic levels and the species: higher taxa ratio. Integrating morphological characteristics (such as body size) that consistently subdivide genera will improve the HTA's performance. Our results are likely applicable to the implementation of the HTA in other small-bodied and species-rich groups and may contribute to the cost-effectiveness of biodiversity surveys.

Profiling crop pollinators: life history traits predict habitat use and crop visitation by Mediterranean wild bees.

Wild pollinators, bees in particular, may greatly contribute to crop pollination and provide a safety net against declines in commercial pollinators. However, the identity, life history traits, and environmental sensitivities of main crop pollinator species.have received limited attention. These are crucial for predicting pollination services of different communities and for developing management practices that enhance crop pollinators. We sampled wild bees in three crop systems (almond, confection sunflower, and seed watermelon) in a mosaic Israeli Mediterranean landscape. Bees were sampled in field/orchard edges and interiors, and in seminatural scrub surrounding the fields/orchards. We also analyzed land cover at 50-2500 m radii around fields/orchards. We used this data to distinguish crop from non-crop pollinators based on a set of life history traits (nesting, lecty, sociality, body size) linked to habitat preference and crop visitation. Bee abundance and species richness decreased from the surrounding seminatural habitat to the field/orchard interior, especially across the seminatural habitat-field edge ecotone. Thus, although rich bee communities were found near fields, only small fractions crossed the ecotone and visited crop flowers in substantial numbers. The bee assemblage in agricultural fields/orchards and on crop flowers was dominated by ground-nesting bees of the tribe Halictini, which tend to nest within fields. Bees' habitat preferences were determined mainly by nesting guild, whereas crop visitation was determined mainly by sociality. Lecty and body size also affected both measures. The percentage of surrounding seminatural habitat at 250-2500 m radii had a positive effect on wild bee diversity in field edges, for all bee guilds, while at 50-100 m radii, only aboveground nesters were positively affected. In sum, we found that crop and non-crop pollinators are distinguished by behavioral and morphological traits. Hence, analysis of life-history traits of bee communities can help assess the pollination services they are likely to provide (when taking into account single-visit pollination efficiency). The ecotone between agricultural fields and surrounding habitats is a major barrier that filters many bee species, particularly with regard to their nesting requirements. Thus, greater attention should be given to management practices that encourage pollinators to live and nest, and not only forage, within fields.

Delivery of crop pollination services is an insufficient argument for wild pollinator conservation.

There is compelling evidence that more diverse ecosystems deliver greater benefits to people, and these ecosystem services have become a key argument for biodiversity conservation. However, it is unclear how much biodiversity is needed to deliver ecosystem services in a cost-effective way. Here we show that, while the contribution of wild bees to crop production is significant, service delivery is restricted to a limited subset of all known bee species. Across crops, years and biogeographical regions, crop-visiting wild bee communities are dominated by a small number of common species, and threatened species are rarely observed on crops. Dominant crop pollinators persist under agricultural expansion and many are easily enhanced by simple conservation measures, suggesting that cost-effective management strategies to promote crop pollination should target a different set of species than management strategies to promote threatened bees. Conserving the biological diversity of bees therefore requires more than just ecosystem-service-based arguments.

How taxonomic diversity, community structure, and sample size determine the reliability of higher taxon surrogates.

Ecologists and paleontologists often rely on higher taxon surrogates instead of complete inventories of biological diversity. Despite their intrinsic appeal, the performance of these surrogates has been markedly inconsistent across empirical studies, to the extent that there is no consensus on appropriate taxonomic resolution (i.e., whether genus- or family-level categories are more appropriate) or their overall usefulness. A framework linking the reliability of higher taxon surrogates to biogeographic setting would allow for the interpretation of previously published work and provide some needed guidance regarding the actual application of these surrogates in biodiversity assessments, conservation planning, and the interpretation of the fossil record. We developed a mathematical model to show how taxonomic diversity, community structure, and sampling effort together affect three measures of higher taxon performance: the correlation between species and higher taxon richness, the relative shapes and asymptotes of species and higher taxon accumulation curves, and the efficiency of higher taxa in a complementarity-based reserve-selection algorithm. In our model, higher taxon surrogates performed well in communities in which a few common species were most abundant, and less well in communities with many equally abundant species. Furthermore, higher taxon surrogates performed well when there was a small mean and variance in the number of species per higher taxa. We also show that empirically measured species-higher-taxon correlations can be partly spurious (i.e., a mathematical artifact), except when the species accumulation curve has reached an asymptote. This particular result is of considerable practical interest given the widespread use of rapid survey methods in biodiversity assessment and the application of higher taxon methods to taxa in which species accumulation curves rarely reach an asymptote, e.g., insects.

A global quantitative synthesis of local and landscape effects on wild bee pollinators in agroecosystems.

Bees provide essential pollination services that are potentially affected both by local farm management and the surrounding landscape. To better understand these different factors, we modelled the relative effects of landscape composition (nesting and floral resources within foraging distances), landscape configuration (patch shape, interpatch connectivity and habitat aggregation) and farm management (organic vs. conventional and local-scale field diversity), and their interactions, on wild bee abundance and richness for 39 crop systems globally. Bee abundance and richness were higher in diversified and organic fields and in landscapes comprising more high-quality habitats; bee richness on conventional fields with low diversity benefited most from high-quality surrounding land cover. Landscape configuration effects were weak. Bee responses varied slightly by biome. Our synthesis reveals that pollinator persistence will depend on both the maintenance of high-quality habitats around farms and on local management practices that may offset impacts of intensive monoculture agriculture.

Wild pollinators enhance fruit set of crops regardless of honey bee abundance.

The diversity and abundance of wild insect pollinators have declined in many agricultural landscapes. Whether such declines reduce crop yields, or are mitigated by managed pollinators such as honey bees, is unclear. We found universally positive associations of fruit set with flower visitation by wild insects in 41 crop systems worldwide. In contrast, fruit set increased significantly with flower visitation by honey bees in only 14% of the systems surveyed. Overall, wild insects pollinated crops more effectively; an increase in wild insect visitation enhanced fruit set by twice as much as an equivalent increase in honey bee visitation. Visitation by wild insects and honey bees promoted fruit set independently, so pollination by managed honey bees supplemented, rather than substituted for, pollination by wild insects. Our results suggest that new practices for integrated management of both honey bees and diverse wild insect assemblages will enhance global crop yields.

Complementary habitat use by wild bees in agro-natural landscapes.

Human activity causes abrupt changes in resource availability across the landscape. In order to persist in human-altered landscapes organisms need to shift their habitat use accordingly. Little is known about the mechanisms by which whole communities persist in human-altered landscapes, including the role of complementary habitat use. We define complementary habitat use as the use of different habitats at different times by the same group of species during the course of their activity period. We hypothesize that complementary habitat use is a mechanism through which native bee species persist in human-altered landscapes. To test this idea, we studied wild bee communities in agro-natural landscapes and explored their community-level patterns of habitat and resource use over space and time. The study was conducted in six agro-natural landscapes in the eastern United States, each containing three main bee habitat types (natural habitat, agricultural fields, and old fields). Each of the three habitats exhibited a unique seasonal pattern in amount, diversity, and composition of floral resources, and together they created phenological complementarity in foraging resources for bees. Individual bee species as well as the bee community responded to these spatiotemporal patterns in floral availability and exhibited a parallel pattern of complementary habitat use. The majority of wild bee species, including all the main crop visitors, used fallow areas within crops early in the season, shifted to crops in mid-season, and used old-field habitats later in the season. The natural-forest habitat supported very limited number of bees, mostly visitors of non-crop plants. Old fields are thus an important feature in these arable landscapes for maintaining crop pollination services. Our study provides a detailed examination of how shifts in habitat and resource use may enable bees to persist in highly dynamic agro-natural landscapes, and points to the need for a broad cross-habitat perspective in managing these landscapes.

Stability of pollination services decreases with isolation from natural areas despite honey bee visits.

Sustainable agricultural landscapes by definition provide high magnitude and stability of ecosystem services, biodiversity and crop productivity. However, few studies have considered landscape effects on the stability of ecosystem services. We tested whether isolation from florally diverse natural and semi-natural areas reduces the spatial and temporal stability of flower-visitor richness and pollination services in crop fields. We synthesised data from 29 studies with contrasting biomes, crop species and pollinator communities. Stability of flower-visitor richness, visitation rate (all insects except honey bees) and fruit set all decreased with distance from natural areas. At 1 km from adjacent natural areas, spatial stability decreased by 25, 16 and 9% for richness, visitation and fruit set, respectively, while temporal stability decreased by 39% for richness and 13% for visitation. Mean richness, visitation and fruit set also decreased with isolation, by 34, 27 and 16% at 1 km respectively. In contrast, honey bee visitation did not change with isolation and represented > 25% of crop visits in 21 studies. Therefore, wild pollinators are relevant for crop productivity and stability even when honey bees are abundant. Policies to preserve and restore natural areas in agricultural landscapes should enhance levels and reliability of pollination services.

Reliability of a higher-taxon approach to richness, rarity, and composition assessments at the local scale.

A promising shortcut for quantifying species patterns is to use genera and families as surrogates of species. At large spatial scales, concurrence between patterns of richness, rarity, and composition of species and higher taxa is generally high. Only a few researchers, however, have examined this relationship at the local scale, which is frequently the relevant scale in land-use conflicts. We investigated the reliability of the higher-taxon approach in assessing patterns of species richness, rarity, and composition at the local scale. We studied diversity patterns of three commonly used surrogate taxa: vascular plants, ground-dwelling beetles, and moths. We conducted year-round field surveys for these taxa in the Jerusalem Mountains and the Judean foothills, Israel. Richness and composition of species were highly correlated with richness and composition of genera for all taxa. At the family level, correlations with richness and composition of species were much lower. Excluding monotypic genera and families did not affect these relations. Rarity representation based on higher taxa varied considerably depending on the taxon, and rarity scale and was weaker compared with richness and composition representation. Cumulative richness curves of species and genera showed similar patterns, leveling off at equivalent sampling efforts. Genus-level assessments were a reliable surrogate for local patterns of species richness, rarity, and composition, but family-level assessments performed poorly. The advantage of using coarse taxonomic scales in local diversity surveys is that it may decrease identification time and the need for experts, but it will not reduce sampling effort.