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Simple Summary: Beekeeping provides numerous economic, cultural, and crop pollination benefits to communities around the world, including in Nepal, where traditional beekeeping has been practiced for centuries. Anecdotal reports suggest that the native Asian honeybee Apis cerana is declining across Asia, but few studies have measured the extent of these declines or their implications for beekeepers and farmers. Working in the Jumla District of Western Nepal, our aims were to investigate population trends of the native honeybee Apis cerana cerana and assess its importance for livelihoods and crop pollination. Interviews with 116 local beekeepers revealed a 44% decline in the number of occupied beehives and a 50% decline in honey production per hive from the years 2012 to 2022. Beekeepers reported climatic changes and the loss of flowers as the main drivers of this decline. These declines pose a major threat to local communities, as sales of honey contribute 16% of total household income for beekeepers, and Apis cerana cerana is a key pollinator of many important crops. Our study provides a warning signal of potential declines in all insect pollinators across the region and calls for actions by farmers, beekeepers, researchers and policy-makers to work together in addressing this socio-ecological crisis. In understudied regions of the world, beekeeper records can provide valuable insights into changes in pollinator population trends. We conducted a questionnaire survey of 116 beekeepers in a mountainous area of Western Nepal, where the native honeybee Apis cerana cerana is kept as a managed bee. We complemented the survey with field data on insect–crop visitation, a household income survey, and an interview with a local lead beekeeper. In total, 76% of beekeepers reported declines in honeybees, while 86% and 78% reported declines in honey yield and number of beehives, respectively. Honey yield per hive fell by 50% between 2012 and 2022, whilst the number of occupied hives decreased by 44%. Beekeepers ranked climate change and declining flower abundance as the most important drivers of the decline. This raises concern for the future food and economic security of this region, where honey sales contribute to 16% of total household income, and where Apis cerana cerana plays a major role in crop pollination, contributing more than 50% of all flower visits to apple, cucumber, and pumpkin. To mitigate further declines, we promote native habitat and wildflower preservation, and using well-insulated log hives to buffer bees against the increasingly extreme temperature fluctuations. [ABSTRACT FROM AUTHOR]

ABSTRACT In recent years, managed honey bee colonies have been suffering from an increasing number of biotic and abiotic stressors, resulting in numerous losses of colonies worldwide. A pan-European study, EPILOBEE, estimated the colony loss in Belgium to be 32.4% in 2012 and 14.8% in 2013. In the current study, absolute viral loads of four known honey bee viruses (DWV-A, DWV-B, AmFV, and BMLV) and three novel putative honey bee viruses (Apis orthomyxovirus 1, apthili virus, and apparli virus) were determined in 300 Flemish honey bee samples, and associations with winter survival were determined. This revealed that, in addition to the known influence of DWV-A and DWV-B on colony health, one of the newly described viruses (apthili virus) shows a strong yearly difference and is also associated with winter survival. Furthermore, all scrutinized viruses revealed significant spatial clustering patterns, implying that despite the limited surface area of Flanders, local virus transmission is paramount. The vast majority of samples were positive for at least one of the seven investigated viruses, and up to 20% of samples were positive for at least one of the three novel viruses. One of those three, Apis orthomyxovirus 1, was shown to be a genuine honey bee-infecting virus, able to infect all developmental stages of the honey bee, as well as the Varroa destructor mite. These results shed light on the most prevalent viruses in Belgium and their roles in the winter survival of honey bee colonies.IMPORTANCEThe western honey bee (Apis mellifera) is a highly effective pollinator of flowering plants, including many crops, which gives honey bees an outstanding importance both ecologically and economically. Alarmingly high annual loss rates of managed honey bee colonies are a growing concern for beekeepers and scientists and have prompted a significant research effort toward bee health. Several detrimental factors have been identified, such as varroa mite infestation and disease from various bacterial and viral agents, but annual differences are often not elucidated. In this study, we utilize the viral metagenomic survey of the EPILOBEE project, a European research program for bee health, to elaborate on the most abundant bee viruses of Flanders. We complement the existing metagenomic data with absolute viral loads and their spatial and temporal distributions. Furthermore, we identify Apis orthomyxovirus 1 as a potentially emerging pathogen, as we find evidence for its active replication honey bees.

Bees are the most important group of insect pollinators, but their populations are declining. To gain a better understanding of wild bee responses to different stressors (e.g. land-use change) and conservation measures, regional and national monitoring schemes are currently being established in Germany, which is used here as a model region, and in many other countries. We offer perspectives on how to best design future bee monitoring programs with a focus on evaluating the implementation of conservation measures. We discuss different traditional and novel sampling methods, their efficacy depending on research questions and the life-history traits of target species, and how greater standardization of wild bee sampling and monitoring methods can make data more comparable, contributing to the identification of general trends and mechanisms driving bee populations. Furthermore, the potential impact of bee sampling itself on bee populations is discussed.

Declines in bumble bee species range and abundances are documented across multiple continents and have prompted the need for research to aid species recovery and conservation. The rusty patched bumble bee (Bombus affinis) is the first federally listed bumble bee species in North America. We conducted a range-wide population genetics study of B. affinis from across all extant conservation units to inform conservation efforts. To understand the species' vulnerability and help establish recovery targets, we examined population structure, patterns of genetic diversity, and population differentiation. Additionally, we conducted a site-level analysis of colony abundance to inform prioritizing areas for conservation, translocation, and other recovery actions. We find substantial evidence of population structuring along an east-to-west gradient. Putative populations show evidence of isolation by distance, high inbreeding coefficients, and a range-wide male diploidy rate of ~15%. Our results suggest the Appalachians represent a genetically distinct cluster with high levels of private alleles and substantial differentiation from the rest of the extant range. Site-level analyses suggest low colony abundance estimates for B. affinis compared to similar datasets of stable, co-occurring species. These results lend genetic support to trends from observational studies, suggesting that B. affinis has undergone a recent decline and exhibit substantial spatial structure. The low colony abundances observed here suggest caution in overinterpreting the stability of populations even where B. affinis is reliably detected interannually. These results help delineate informed management units, provide context for the potential risks of translocation programs, and help set clear recovery targets for this and other threatened bumble bee species. [ABSTRACT FROM AUTHOR]

Bees are the most important group of insect pollinators, but their populations are declining. To gain a better understanding of wild bee responses to different stressors (e.g. land-use change) and conservation measures, regional and national monitoring schemes are currently being established in Germany, which is used here as a model region, and in many other countries. We offer perspectives on how to best design future bee monitoring programs with a focus on evaluating the implementation of conservation measures. We discuss different traditional and novel sampling methods, their efficacy depending on research questions and the life-history traits of target species, and how greater standardization of wild bee sampling and monitoring methods can make data more comparable, contributing to the identification of general trends and mechanisms driving bee populations. Furthermore, the potential impact of bee sampling itself on bee populations is discussed. [ABSTRACT FROM AUTHOR]

This paper describes Percorso Impollinatori (Tracing a Pollinator’s Path), a transdisciplinary citizen engagement project aiming to address the decline of wild pollinating insects via material deliberation methods. Following a participatory design approach, three different participatory actions were co-designed and prototyped in two locations in Italy as experimental instances of material deliberation methods, incorporating citizens, farmers, scientific experts, and artistic professionals into collaborative assemblages. This project identified material deliberation as a way to address epistemic pluralism, meaning that the non-discursive, artistic, and embodied modes of knowing were applied in combination with the more formal, scientific disciplines. Three participatory actions were specifically meant for the collaboration of local citizens and farmers, aiming: (1) to reflect on their personal experiences of pollinators and pollination, (2) to rethink the values they attribute to such experiences and to pollination services, (3) to reframe the pollinator decline issue from locally focused ecological and cultural perspectives, and (4) to generate collaborative ideas to invert the decline and let pollinating insects thrive. Drawing from Lattanzi’s definition of transdisciplinarity as disciplinary “outerspace” and anthropologist Ingold’s concept of correspondence, I (as the leading researcher and project designer) reflect on the collaborative assemblages constructed for each participatory action and on the dynamics enabled among their members, which allowed the emergence of transdisciplinary outcomes. I describe the participatory actions, focusing on how each unfolded through a preparatory and enactment phase, and the learning collected from each one. I conclude by suggesting that both in the preparation and in the enactment of the material deliberation methods, the activation of correspondence dynamics within the collaborative assemblages elicited the emergence of transdisciplinarity around the issue of pollinator decline. Future researchers are invited to reiterate the design and implementation process in other complex and conflictual sustainability contexts.

As reported by experimental studies, changes in pollination regime are expected to drive plant mating system evolution. In natural populations facing pollinator decline, plant-mating system is thus susceptible to evolve. We analyzed the demographic consequences of such evolution and if such evolution can rescue populations. We developed a quantitative genetic model for evolution after a pollinator crash and we analyzed the demographic consequences over a few dozens of generations. The model considers two sources of stochasticity. Contrary to classical models, inbreeding depression is considered as a probabilistic event affecting differentially inbred and outbred individuals (demographic stochasticity). Pollination is also considered as a probabilistic event (environmental stochasticity). The model is derived under (1) infinite population size and (2) finite population size. The results highlight three generic evolutionary scenarios. The evolution of selfing after a pollinator crash can rescue populations but can sometimes lead to evolutionary suicide. While the genetic variance of mating system traits determines the pace of evolution, initial population sizes determine the countdown for evolution to rescue population making stochastic extinction likely in small populations. Our model shows that evolution may not save populations due to frequency-dependent selection acting on mating system. We propose an alternative interpretation for the higher extinction rate of selfing taxa and we discuss its implications for plant conservation. [ABSTRACT FROM AUTHOR]

Human‐mediated environmental change, by reducing mean fitness, is hypothesized to strengthen selection on traits that mediate interactions among species. For example, human‐mediated declines in pollinator populations are hypothesized to reduce mean seed production by increasing the magnitude of pollen limitation and thus strengthen pollinator‐mediated selection on floral traits that increase pollinator attraction or pollen transfer efficiency. To test this hypothesis, we measured two female fitness components and six floral traits of Lobelia siphilitica plants exposed to supplemental hand‐pollination, ambient open‐pollination, or reduced open‐pollination treatments. The reduced treatment simulated pollinator decline, while the supplemental treatment was used to estimate pollen limitation and pollinator‐mediated selection. We found that plants in the reduced pollination treatment were significantly pollen limited, resulting in pollinator‐mediated selection for taller inflorescences and more vibrant petals, both traits that could increase pollinator attraction. This contrasts with plants in the ambient pollination treatment, where reproduction was not pollen limited and there was not significant pollinator‐mediated selection on any floral trait. Our results support the hypothesis that human‐mediated environmental change can strengthen selection on traits of interacting species and suggest that these traits have the potential to evolve in response to changing environments. [ABSTRACT FROM AUTHOR]

Since mid‐1990s, concerns have increased about a human‐induced "pollination crisis." Threats have been identified to animals that act as plant pollinators, plants pollinated by these animals, and consequently human well‐being. Threatening processes include loss of natural habitat, climate change, pesticide use, pathogen spread, and introduced species. However, concern has mostly been during last 10–15 years and from Europe and North America, with Australasia, known as Down‐Under, receiving little attention. So perhaps Australasia has "dodged the bullet"? We systematically reviewed the published literature relating to the "pollination crisis" via Web of Science, focusing on issues amenable to this approach. Across these issues, we found a steep increase in publications over the last few decades and a major geographic bias towards Europe and North America, with relatively little attention in Australasia. While publications from Australasia are underrepresented, factors responsible elsewhere for causing the "pollination crisis" commonly occur in Australasia, so this lack of coverage probably reflects a lack of awareness rather than the absence of a problem. In other words, Australasia has not "dodged the bullet" and should take immediate action to address and mitigate its own "pollination crisis." Sensible steps would include increased taxonomic work on suspected plant pollinators, protection for pollinator populations threatened with extinction, establishing long‐term monitoring of plant–pollinator relationships, incorporating pollination into sustainable agriculture, restricting the use of various pesticides, adopting an Integrated Pest and Pollinator Management approach, and developing partnerships with First Nations peoples for research, conservation and management of plants and their pollinators. Appropriate Government policy, funding and regulation could help. [ABSTRACT FROM AUTHOR]

Abstract Since mid‐1990s, concerns have increased about a human‐induced “pollination crisis.” Threats have been identified to animals that act as plant pollinators, plants pollinated by these animals, and consequently human well‐being. Threatening processes include loss of natural habitat, climate change, pesticide use, pathogen spread, and introduced species. However, concern has mostly been during last 10–15 years and from Europe and North America, with Australasia, known as Down‐Under, receiving little attention. So perhaps Australasia has “dodged the bullet”? We systematically reviewed the published literature relating to the “pollination crisis” via Web of Science, focusing on issues amenable to this approach. Across these issues, we found a steep increase in publications over the last few decades and a major geographic bias towards Europe and North America, with relatively little attention in Australasia. While publications from Australasia are underrepresented, factors responsible elsewhere for causing the “pollination crisis” commonly occur in Australasia, so this lack of coverage probably reflects a lack of awareness rather than the absence of a problem. In other words, Australasia has not “dodged the bullet” and should take immediate action to address and mitigate its own “pollination crisis.” Sensible steps would include increased taxonomic work on suspected plant pollinators, protection for pollinator populations threatened with extinction, establishing long‐term monitoring of plant–pollinator relationships, incorporating pollination into sustainable agriculture, restricting the use of various pesticides, adopting an Integrated Pest and Pollinator Management approach, and developing partnerships with First Nations peoples for research, conservation and management of plants and their pollinators. Appropriate Government policy, funding and regulation could help.

Abstract Human‐mediated environmental change, by reducing mean fitness, is hypothesized to strengthen selection on traits that mediate interactions among species. For example, human‐mediated declines in pollinator populations are hypothesized to reduce mean seed production by increasing the magnitude of pollen limitation and thus strengthen pollinator‐mediated selection on floral traits that increase pollinator attraction or pollen transfer efficiency. To test this hypothesis, we measured two female fitness components and six floral traits of Lobelia siphilitica plants exposed to supplemental hand‐pollination, ambient open‐pollination, or reduced open‐pollination treatments. The reduced treatment simulated pollinator decline, while the supplemental treatment was used to estimate pollen limitation and pollinator‐mediated selection. We found that plants in the reduced pollination treatment were significantly pollen limited, resulting in pollinator‐mediated selection for taller inflorescences and more vibrant petals, both traits that could increase pollinator attraction. This contrasts with plants in the ambient pollination treatment, where reproduction was not pollen limited and there was not significant pollinator‐mediated selection on any floral trait. Our results support the hypothesis that human‐mediated environmental change can strengthen selection on traits of interacting species and suggest that these traits have the potential to evolve in response to changing environments.

Plants modulate multitrophic ecological interactions, and variation in plant traits can affect these interactions. Pollinators are exposed to pathogens at flowers and acquire or transmit pathogens at different rates on different plant species, but the traits mediating those interactions are almost entirely unknown. We experimentally manipulated five plant traits that span scales including flower, inflorescence, and plant, to determine their effects on pathogen transmission between foraging bees. Specifically, we manipulated two morphological traits (corolla lip length and flower orientation within an inflorescence) and three resource distribution traits (inflorescence nectar, plant patch nectar, and plant aggregation) in tents to test how plant traits affect bee pathogen transmission. We also quantified foraging behavior and fecal deposition patterns as potential mechanisms driving differences in transmission, and assessed trait manipulation consequences for bee reproduction. We found that pathogen transmission was reduced when we trimmed the corolla lip, evenly dispersed nectar distribution within an inflorescence, or aggregated plants in space. Some traits also affected bee reproduction; tents with trimmed corollas had more larval production than control tents, and tents with evenly distributed nectar across plant patches had more larval production than tents with clumped resources. Thus, some trait manipulations both reduced transmission and increased bee microcolony reproduction, although our design does not allow us to discern whether these are related or separate effects. Taken together, our results demonstrate causal effects of several floral traits on pathogen transmission and pollinator reproduction, indicating the importance of intraspecific plant trait variation for pollinator health and population dynamics. [ABSTRACT FROM AUTHOR]

Crop yields, i.e. harvestable production per unit of cropland area, are in decline for a number of crops and regions, but the drivers of this process are poorly known. Global decreases in pollinator abundance and diversity have been proposed as a major driver of yield declines in crops that depend on animals, mostly bees, to produce fruits and seeds. Alternatively, widespread tree mortality has been directly and indirectly related to global climate change, which could also explain yield decreases in tree crops. As tree crops are expected to be more dependent on pollinators than other crop types, disentangling the relative influence of growth form and pollinator dependence is relevant to identify the ultimate factors driving yield declines. Yield decline, defined here as a negative average annual yearly change in yield from 1961 to 2020, was measured in 4270 time series, involving 136 crops and 163 countries and territories. About one‑fourth of all time series showed declines in crop yield, a characteristic associated with both high pollinator dependence and a tree growth form. Because pollinator dependence and plant growth form were partially correlated, we disentangled the effect of each of these two predictors using a series of generalized linear mixed models that evaluated direct and indirect associations. Our analyses revealed a stronger association of yield decline with growth form than with pollinator dependence, a relationship that persisted after partialling out the effect of pollinator dependence. In particular, yield declines were more common among tree than herbaceous and shrub crops in all major regions but in Africa, a continent showing a high incidence of yield declines irrespective of growth form. These results suggest that pollinator decline is not the main reason behind crop productivity loss, but that other factors such as climate change could be already affecting crop yield.

Gut symbionts can augment resistance to pathogens by stimulating host-immune responses, competing for space and nutrients, or producing antimicrobial metabolites. Gut microbiota of social bees, which pollinate many crops and wildflowers, protect hosts against diverse infections and might counteract pathogen-related bee declines. Bumble bee gut microbiota, and specifically abundance of Lactobacillus Firm-5 bacteria, can enhance resistance to the trypanosomatid parasite Crithidia bombi. However, the mechanism underlying this effect remains unknown. We hypothesized that the Firm-5 bacterium Lactobacillus bombicola, which produces lactic acid, inhibits C. bombi via pH-mediated effects. Consistent with our hypothesis, L. bombicola spent medium inhibited C. bombi growth via reduction in pH that was both necessary and sufficient for inhibition. Inhibition of all parasite strains occurred within the pH range documented in honey bees, though sensitivity to acidity varied among strains. Spent medium was slightly more potent than HCl, d- and l-lactic acids for a given pH, suggesting that other metabolites also contribute to inhibition. Results implicate symbiont-mediated reduction in gut pH as a key determinant of trypanosomatid infection in bees. Future investigation into in vivo effects of gut microbiota on pH and infection intensity would test the relevance of these findings for bees threatened by trypanosomatids.

In a study of 220 eastern bumblebee specimens collected from the Roanoke and New River Valley areas, PCR analysis of the gut lumen revealed the absence of Nosema spp. infections, challenging prevailing assumptions about their prevalence in bumblebee populations. The outcome underscores the need for further research to determine the factors contributing to this absence, including the unique ecological context of the study area. These findings highlight the significance of host susceptibility and survivability, emphasizing the complexity associated with parasite-host interactions within bumblebees. [ABSTRACT FROM AUTHOR]

Premise: In the absence of hawkmoth pollinators, chasmogamous (CH) flowers of Ruellia humilis self‐pollinate by two secondary mechanisms. Other floral visitors might exert selection on CH floral traits to restore outcrossing, but at the same time preferential predation of CH seeds generates selection to increase the allocation of resources to cleistogamous (CL) flowers. Methods: To assess the potential for an evolutionary response to these competing selection pressures, we estimated additive genetic variances (σA2 ${\sigma }_{{\rm{A}}}^{2}$) and covariances for 14 reproductive traits and three fitness components in a Missouri population lacking hawkmoth pollinators. Results: We found significant σA2 ${\sigma }_{{\rm{A}}}^{2}$ for all 11 floral traits and two measures of resource allocation to CL flowers, indicating the potential for a short‐term response to selection on most reproductive traits. Selection generated by seed predators is predicted to increase the percentage of CL flowers by 0.24% per generation, and mean stigma–anther separation is predicted to decrease as a correlated response, increasing the fraction of plants that engage in prior selfing. However, the initial response to this selection is opposed by strong directional dominance. Conclusions: The predicted evolutionary decrease in the number of CH flowers available for potential outcrossing, combined with the apparent preclusion of potential diurnal pollinators by the pollen‐harvesting activities of sweat bees, suggest that 100% cleistogamy is the likely outcome of evolution in the absence of hawkmoths. However, rare mutations with large effects, such as delaying budbreak until after sunrise, could provide pathways for the restoration of outcrossing that are not reachable by gradual quantitative‐genetic evolution. [ABSTRACT FROM AUTHOR]

Premise: As part of global change, climate warming and pollinator decline are expected to affect plant phenology and plant–pollinator interactions. This paper aims at characterizing rapid evolution of life history traits and floral traits over two decades in the wild pansy (Viola arvensis), a common weed in agrosystems. Methods: We used a resurrection ecology approach with genotypes sampled in 1991 and 2012 from a population in Burgundy (France). The species has a mixed mating system (hereafter: mixed selfer) and presents a floral polymorphism. To correct for maternal effects, we measured plant traits in the second generation in a common garden (after a refreshing generation) to characterize plant evolution during the two decades. In addition, historical population selfing rates in 1991 and 2012 were inferred from microsatellites markers through heterozygote deficiency and identity disequilibrium. Results: Phenotypic data revealed a significant advance in flowering date, reduced flower sizes and a higher propensity of plants to set seed by autonomous selfing. Moreover, we detected a change in color morph frequency with an increase of the pale morph frequency. In accordance with phenotypic data, the neutral genetic data revealed an increase in historical selfing rates from 0.68 in 1991 to 0.86 in 2012. Conclusions: Taken together, such data suggest that the wild pansy, a mixed selfer, is evolving a selfing syndrome that may be the consequence of reduced pollinator activity in agrosystems. [ABSTRACT FROM AUTHOR]

This article is a Commentary on Acoca‐Pidolle et al. (2023), 242: 717–726. [ABSTRACT FROM AUTHOR]

Mounting evidence shows that pollinators are declining as a result of widespread environmental degradation. This loss raises concerns that a global pollination crisis could threaten the human food supply by decreasing crop yield and even promote famine under a hypothetical scenario of total pollinator extinction. This catastrophic possibility has prompted intense interest from scientists, politicians and the general public. However, three lines of evidence do not support such an apocalyptic scenario. First, even though the abundance and diversity of wild pollinators are declining worldwide, the global population of managed honey-bee hives has increased by ~80% since the early 1960s. Second, agricultural production would decrease by <10% in the total absence of bees because relatively few crops are completely pollinator dependent. Lastly, despite widespread pollination deficits, current evidence is inconsistent with deceleration in yield growth with increasing pollinator dependence at a global scale, probably due to improvements in crop breeding and external agricultural subsidies. Overall, this evidence refutes simplistic claims of human starvation caused by a hypothetical total pollinator extinction. Nevertheless, pollination problems may loom. Although pollinators are responsible for a minor fraction of global agriculture production, this fraction has increased ~600% since 1961, greatly outpacing human population growth and the growth of the global population of managed honey bees. This large production increase is explained to a considerable extent by the rapid expansion of pollinator- dependent monocultures at the expense of natural and diverse agricultural habitats. By driving pollinator decline, this land-use transformation could worsen pollination deficits and promote further crop expansion given sustained market demands. Therefore, although the human food supply is not currently subject to a global pollination crisis, a spiralling positive-feedback between the impacts of agriculture expansion and pollinator decline on crop yield could accelerate precipitous biodiversity loss by promoting further habitat destruction and homogenization. [ABSTRACT FROM AUTHOR]

European honeybee populations are considered to consist only of managed colonies, but recent censuses have revealed that wild/feral colonies still occur in various countries. To gauge the ecological and evolutionary relevance of wild-living honeybees, information is needed on their population demography. We monitored feral honeybee colonies in German forests for up to 4 years through regular inspections of woodpecker cavity trees and microsatellite genotyping. Each summer, about 10% of the trees were occupied, corresponding to average densities of 0.23 feral colonies km−2 (an estimated 5% of the regional honeybee populations). Populations decreased moderately until autumn but dropped massively during winter, so that their densities were only about 0.02 colonies km−2 in early spring. During the reproductive (swarming) season, in May and June, populations recovered, with new swarms preferring nest sites that had been occupied in the previous year. The annual survival rate and the estimated lifespan of feral colonies (n = 112) were 10.6% and 0.6 years, respectively. We conclude that managed forests in Germany do not harbour self-sustaining feral honeybee populations, but they are recolonized every year by swarms escaping from apiaries.

Despite a substantial increase in scientific, public and political interest in pollinator health and many practical conservation efforts, incorporating initiatives across a range of scales and sectors, pollinator health continues to decline. We review existing pollinator conservation initiatives and define their common structural elements. We argue that implementing effective action for pollinators requires further scientific understanding in six key areas: (i) status and trends of pollinator populations; (ii) direct and indirect drivers of decline, including their interactions; (iii) risks and co-benefits of pollinator conservation actions for ecosystems; (iv) benefits of pollinator conservation for society; (v) the effectiveness of context-specific, tailored, actionable solutions; and (vi) integrated frameworks that explicitly link benefits and values with actions to reverse declines. We propose use of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) conceptual framework to link issues and identify critical gaps in both understanding and action for pollinators. This approach reveals the centrality of addressing the recognized indirect drivers of decline, such as patterns of global trade and demography, which are frequently overlooked in current pollinator conservation efforts. Finally, we discuss how existing and new approaches in research can support efforts to move beyond these shortcomings in pollinator conservation initiatives. This article is part of the theme issue 'Natural processes influencing pollinator health: from chemistry to landscapes'. [ABSTRACT FROM AUTHOR]

(1) Land use intensification has led to serious declines in biodiversity, including in forage production systems for dairy cows. Agri-environmental schemes, such as enriching grasslands in floral species, were shown to be an effective tool to promote biodiversity in higher trophic levels. Here, we studied an innovative pasture-based dairy production system with floral-species-enhanced temporary grasslands, with respect to the effect on wild bee abundance and species richness. (2) We studied three grass-clover mixtures with perennial ryegrass and clover species with different levels of plant diversity for flower cover and wild bees. The grass-clover pastures were rotationally stocked with cattle and parts of the pastures were excluded from grazing. Intensively managed conventional permanent grasslands were studied as the common land use type. Wild bees were caught by sweep netting. Wild bee diversity was analysed with a general linear mixed model. For species richness, an incidence-based coverage estimator was calculated. (3) In total, 541 wild bees from 10 species were found. No wild bees were caught on the conventional grasslands. Wild bee abundance and species richness did not differ among the three grass-clover mixtures, but with increasing flower cover of white clover (Trifolium repens), wild bee abundance increased. Except for one solitary wild bee individual, the recorded community exclusively consisted of bumblebees. While generalist species that are commonly found on farmland dominated, rare long-tongued bumblebees made up 10% on the grazed sites of the multispecies mixture and made up 20% on the ungrazed strips of the binary mixture and multispecies mixture. (4) We conclude that multispecies mixtures can provide resources for generalist bumblebee species, especially when compared with conventional grasslands that offer no resources. Considering that the multispecies mixture has been also shown to reduce greenhouse gas emissions and nitrate leaching, while maintaining high forage yields, our findings add to the potential to promote a wide range of ecosystem services. Yet, should their full potential be enfolded, grazing should partially be excluded, and the mixture should be extended by plant species with more open flowers, suitable for solitary wild bees. [ABSTRACT FROM AUTHOR]

The conservation status of pollinators and pollination in Latin America (LA) is reviewed. The knowledge regarding native and managed pollinators (e.g., honeybee and stingless bees) and pollination services was synthetized, and the guidelines to improve the opportunities for conservation are provided, considering the threats to pollinators and the perspectives from traditional and local knowledge. The analysis indicates that diverse threats (e.g., large-scale agriculture, deforestation, overuse of agrochemicals) are linked with pollination and pollinator decline, which affect the reproduction of most native plants and the yields of many crops. LA harbours the highest bee diversity worldwide, with 26% of the total recorded species, and it is a biodiversity hotspot of vertebrate pollinators, including hummingbirds, perching birds, nectarivorous bats and other mammal pollinators. Specific recommendations to conserve native pollinators and to improve pollination services are provided, which could be considered by stakeholders and governments aiming to elaborate biocultural conservation. For example, introducing policies and legal responses for incentives to help farmers maintain natural habitats and forests, to replace or reduce agrochemicals and to improve diversified crop production with agroecological practices; refining agrochemical regulations to minimize the exposure of pollinators to insecticides and herbicides; improving knowledge and education on pollinators and pollination gives societies worldwide the opportunity to change current hegemonic agricultural practices and consumption patterns; integrating different land ethical views of ethnic minorities on a sustainable relationship between production and biodiversity. A wider view combining social, ecological, cultural dimensions may support better decision making. This holistic socio-agroecological perspective is urgently needed to conserve and manage pollinators at different spatial and temporal scales, and to integrate pollination services, pollinator-friendly habitat management approaches and diversified farming systems. [ABSTRACT FROM AUTHOR]

The lack of consensus regarding pollinator decline in various parts of the planet has generated intense debates in different spheres. Consequently, much research has attempted to identify the leading causes of this decline, and a multifactorial synergism (i.e., different stressors acting together and mutually potentiating the harmful effects) seems to be the emerging consensus explaining this phenomenon. The emphasis on some stressor groups such as agrochemicals, and pollinators such as the honey bee Apis mellifera, can hide the real risk of anthropogenic stressors on pollinating insects. In the present study, we conducted a systematic review of the literature to identify general and temporal trends in publications, considering the different groups of pollinators and their exposure to agrochemicals over the last 76 years. Through an artificial intelligence (AI)-aided meta-analysis, we quantitatively assessed trends in publications on bee groups and agrochemicals. Using AI tools through machine learning enabled efficient evaluation of a large volume of published articles. Toxicological assessment of the impact of agrochemicals on insect pollinators is dominated by the order Hymenoptera, which includes honey bees. Although honey bees are well-explored, there is a lack of published articles exploring the toxicological assessment of agrochemicals for bumble bees, solitary bees, and stingless bees. The data gathered provide insights into the current scenario of the risk of pollinator decline imposed by agrochemicals and serve to guide further research in this area.Systematic Review Registrationhttps://asreview.nl/.

The conservation status of pollinators and pollination in Latin America (LA) is reviewed. The knowledge regarding native and managed pollinators (e.g., honeybee and stingless bees) and pollination services was synthetized, and the guidelines to improve the opportunities for conservation are provided, considering the threats to pollinators and the perspectives from traditional and local knowledge. The analysis indicates that diverse threats (e.g., large-scale agriculture, deforestation, overuse of agrochemicals) are linked with pollination and pollinator decline, which affect the reproduction of most native plants and the yields of many crops. LA harbours the highest bee diversity worldwide, with 26% of the total recorded species, and it is a biodiversity hotspot of vertebrate pollinators, including hummingbirds, perching birds, nectarivorous bats and other mammal pollinators. Specific recommendations to conserve native pollinators and to improve pollination services are provided, which could be considered by stakeholders and governments aiming to elaborate biocultural conservation. For example, introducing policies and legal responses for incentives to help farmers maintain natural habitats and forests, to replace or reduce agrochemicals and to improve diversified crop production with agroecological practices; refining agrochemical regulations to minimize the exposure of pollinators to insecticides and herbicides; improving knowledge and education on pollinators and pollination gives societies worldwide the opportunity to change current hegemonic agricultural practices and consumption patterns; integrating different land ethical views of ethnic minorities on a sustainable relationship between production and biodiversity. A wider view combining social, ecological, cultural dimensions may support better decision making. This holistic socio-agroecological perspective is urgently needed to conserve and manage pollinators at different spatial and temporal scales, and to integrate pollination services, pollinator-friendly habitat management approaches and diversified farming systems.

In recent years, managed honey bee colonies have been suffering from an increasing number of biotic and abiotic stressors, resulting in numerous losses of colonies worldwide. A pan-European study, EPILOBEE, estimated the colony loss in Belgium to be 32.4% in 2012 and 14.8% in 2013. In the current study, absolute viral loads of four known honey bee viruses (DWV-A, DWV-B, AmFV, and BMLV) and three novel putative honey bee viruses (Apis orthomyxovirus 1, apthili virus, and apparli virus) were determined in 300 Flemish honey bee samples, and associations with winter survival were determined. This revealed that, in addition to the known influence of DWV-A and DWV-B on colony health, one of the newly described viruses (apthili virus) shows a strong yearly difference and is also associated with winter survival. Furthermore, all scrutinized viruses revealed significant spatial clustering patterns, implying that despite the limited surface area of Flanders, local virus transmission is paramount. The vast majority of samples were positive for at least one of the seven investigated viruses, and up to 20% of samples were positive for at least one of the three novel viruses. One of those three, Apis orthomyxovirus 1, was shown to be a genuine honey bee-infecting virus, able to infect all developmental stages of the honey bee, as well as the Varroa destructor mite. These results shed light on the most prevalent viruses in Belgium and their roles in the winter survival of honey bee colonies., Importance: The western honey bee ( Apis mellifera ) is a highly effective pollinator of flowering plants, including many crops, which gives honey bees an outstanding importance both ecologically and economically. Alarmingly high annual loss rates of managed honey bee colonies are a growing concern for beekeepers and scientists and have prompted a significant research effort toward bee health. Several detrimental factors have been identified, such as varroa mite infestation and disease from various bacterial and viral agents, but annual differences are often not elucidated. In this study, we utilize the viral metagenomic survey of the EPILOBEE project, a European research program for bee health, to elaborate on the most abundant bee viruses of Flanders. We complement the existing metagenomic data with absolute viral loads and their spatial and temporal distributions. Furthermore, we identify Apis orthomyxovirus 1 as a potentially emerging pathogen, as we find evidence for its active replication honey bees., Competing Interests: The authors declare no conflict of interest.

Global change is expected to drive short‐term evolution of natural populations. However, it remains unclear whether different populations are changing in unison. Here, we study contemporary evolution of growth‐related and reproductive traits of three populations of Cyanus segetum facing warming and pollinator decline across a latitudinal gradient in France. We resurrected stored seeds sampled up to 24 years apart from northern, central‐western, and southern populations and conducted an in situ common‐garden experiment. To disentangle neutral from selection‐driven differentiation, we calculated neutral genetic differentiation (FST) and quantitative trait differentiation (QST) between temporal samples. We found that phenotypic evolution was divergent across populations exhibiting different trends for rosette size, date of flowering, and capitula size. By measuring seed set as a proxy of fitness, we showed that samples with larger mean capitula size outperformed samples with smaller mean capitula size in the western and southern populations. Regression of traits on seed set showed that flowering date and capitula size are the primary determinants of fitness, and QST‐FST comparisons indicated that natural selection has likely contributed to the shifts in flowering phenology and rosette size. These findings outline the potential for rescue of natural populations through contemporary evolution and emphasize the complex interplay between spatial and temporal variation in species' responses to global change. [ABSTRACT FROM AUTHOR]

Finally, to investigate the relation between THS and the conservation status of the analyzed species (Nieto et al. 2014), we used the population trend estimation proposed by the International Union for Conservation of Nature (IUCN) to sort sampled species according to their IUCN population trend categories: unknown, decreasing, stable, and increasing. Integrative taxonomy of an arctic bumblebee species complex highlights a new cryptic species (Apidae: Bombus). Results Variability in Heat Stress Resistance of Bumblebees We measured THS for 2386 bumblebee males belonging to 39 species (Fig. Keywords: climate change; extreme events; pollinator decline; heat resistance; inter- and intraspecific variability; cambio climático; declinación de polinizadores; eventos extremos; resistencia al calor; variabilidad inter- e intraespecífica EN climate change extreme events pollinator decline heat resistance inter- and intraspecific variability cambio climático declinación de polinizadores eventos extremos resistencia al calor variabilidad inter- e intraespecífica 1507 1518 12 10/05/21 20211001 NES 211001 Introduction Since the turn of the 20th century, human activities have triggered global warming, resulting in an average temperature increase of 0.85 °C (Hance et al. 2007). [Extracted from the article]

Trait variation can have important consequences for the outcomes of species interactions. Even though some traits vary as much within species as across related species, models and empirical studies typically do not consider the role of intraspecific trait variation for processes such as disease transmission. For example, many pollinator species are in decline because of a variety of stressors including pathogens, but the role of intraspecific trait variation in mediating disease dynamics is rarely considered. For example, pollinator body size could affect pathogen transmission via differences in resistance, foraging behavior and physiology. We tested effects of body size on pollinator pathogen transmission using the common eastern bumble bee Bombus impatiens in field tents, introducing an infected "donor" microcolony of large or small workers with an uninfected average‐sized "recipient" microcolony and allowing bees to forage for 9–16 d. Small donor bees had nearly 50% higher infection intensity (cells/0.02 μL) than large donor bees, but large donor bees were twice as likely to transmit Crithidia bombi to recipient bees. Both behavioral and physiological mechanisms may underlie this apparent paradox. Compared to small bees, large bees foraged more and produced more feces; simulations showed that foraging and defecation rates together had stronger effects on transmission than did donor infection intensity. Thus, effects of bee size on contact rates and pathogen supply may play significant roles in disease transmission, demonstrating the multifaceted impacts of traits on transmission dynamics. [ABSTRACT FROM AUTHOR]

Abstract Greater pollination intensity can enhance maternal plant fitness by increasing seed set and seed quality as a result of more intense pollen competition or enhanced genetic sampling. We tested experimentally these effects by varying the pollen load from a single pollen donor on stigmas of female flowers of Dalechampia scandens (Euphorbiaceae) and measuring the effects on seed number and seed mass. Seed set increased rapidly with pollen number at low to moderate pollen loads, and a maximum set of three seeds occurred with a mean pollen load of 19 pollen grains. We did not detect a trade‐off between the number of seeds and seed mass within a fruit. Seed mass increased with increasing pollen load, supporting the hypothesis of enhanced seed quality via increased pollen‐competition intensity or genetic sampling. These results suggest that maternal fitness increases with larger pollen loads, even when the fertilization success is already high. Our results further highlight the importance of high rates of pollen arrival onto stigmas, as mediated by reliable pollinators. Comparing the pollen‐to‐seed response curve obtained in this experiment with those observed in natural populations suggests that pollen limitation may be more severe in natural populations than predicted from greenhouse studies. These results also indicate that declines in pollinator abundance may decrease plant fitness through lowered seed quality before an effect on seed set is detected.

The number of pollinators has been reported to be decreasing for the past several decades. Numerous sources (e.g., climate change, pesticides, loss of habitat) have been noted as potential contributing factors to the decline. With respect to the green industry, the impact of pesticides on pollinator decline and consumer response to this impact is of critical importance. Although no definitive link exists of pesticides being a major contributing factor to pollinator decline, some retailers have banned their suppliers from using certain pesticides. As various sources (e.g., universities, media, activist groups) provide information (both positive, neutral, and negative) about the impact of pesticides on pollinators, no information exists regarding how consumers value such information. Using a sample of Connecticut consumers, this study evaluates how both information source and information type impact a consumer’s decision to purchase pollinator-friendly plants in the future. The study finds that consumers exposed to either neutral (no link between pesticides and pollinator decline) or negative (link between pesticides and pollinator decline) information from universities and major media outlets indicate they will purchase more pollinator-friendly plants compared with the no information (control) treatment. The results show that information from the federal government, nursery/greenhouse industry associations, and environmental activist groups have the same impact on self-reported future pollinator-friendly plant purchasing as the no information group.

(1) Land use intensification has led to serious declines in biodiversity, including in forage production systems for dairy cows. Agri-environmental schemes, such as enriching grasslands in floral species, were shown to be an effective tool to promote biodiversity in higher trophic levels. Here, we studied an innovative pasture-based dairy production system with floral-species-enhanced temporary grasslands, with respect to the effect on wild bee abundance and species richness. (2) We studied three grass-clover mixtures with perennial ryegrass and clover species with different levels of plant diversity for flower cover and wild bees. The grass-clover pastures were rotationally stocked with cattle and parts of the pastures were excluded from grazing. Intensively managed conventional permanent grasslands were studied as the common land use type. Wild bees were caught by sweep netting. Wild bee diversity was analysed with a general linear mixed model. For species richness, an incidence-based coverage estimator was calculated. (3) In total, 541 wild bees from 10 species were found. No wild bees were caught on the conventional grasslands. Wild bee abundance and species richness did not differ among the three grass-clover mixtures, but with increasing flower cover of white clover (Trifolium repens), wild bee abundance increased. Except for one solitary wild bee individual, the recorded community exclusively consisted of bumblebees. While generalist species that are commonly found on farmland dominated, rare long-tongued bumblebees made up 10% on the grazed sites of the multispecies mixture and made up 20% on the ungrazed strips of the binary mixture and multispecies mixture. (4) We conclude that multispecies mixtures can provide resources for generalist bumblebee species, especially when compared with conventional grasslands that offer no resources. Considering that the multispecies mixture has been also shown to reduce greenhouse gas emissions and nitrate leaching, while maintaining high forage yields, our findings add to the potential to promote a wide range of ecosystem services. Yet, should their full potential be enfolded, grazing should partially be excluded, and the mixture should be extended by plant species with more open flowers, suitable for solitary wild bees.

Abstract Population declines of pollinators constitute a major concern for the fate of biodiversity and associated ecosystem services in a context of global change. Massive declines of pollinator populations driven by habitat loss, pollution, and climate change have been reported, whose consequences at community and ecosystem levels remain elusive. We conducted a mathematical modeling and computer simulation study to assess the dynamic consequences of pollinator declines for the biodiversity of plants and pollinators. Specifically, we evaluated the effects of increased mortality and decreased carrying capacity of specialist vs. generalist and effective vs. ineffective pollinators visiting specialist vs. generalist plants on long‐term community biomass and species persistence. Our results reveal that increased larval mortality and increased competition for space among larvae had the greatest impacts on the decline of pollinator diversity. In contrast, the largest sustained decreases in pollinator biomass were driven by increased adult mortality in spite of a small increase in pollinator species persistence. Decreased pollinator diversity led in turn to decreased plant diversity. Attacking pollinators with high degree and connected mostly to low‐degree plants produced the greatest losses of plant diversity. Pollinator effectiveness had no noticeable effect on persistence. Our results illuminate our understanding of the consequences of pollinator declines for the maintenance of biodiversity.

Pathogens pose significant threats to pollinator health and food security. Pollinators can transmit diseases during foraging, but the consequences of plant species composition for infection is unknown. In agroecosystems, flowering strips or hedgerows are often used to augment pollinator habitat. We used canola as a focal crop in tents and manipulated flowering strip composition using plant species we had previously shown to result in higher or lower bee infection in short-term trials. We also manipulated initial colony infection to assess impacts on foraging behavior. Flowering strips using high-infection plant species nearly doubled bumble bee colony infection intensity compared to low-infection plant species, with intermediate infection in canola-only tents. Both infection treatment and flowering strips reduced visits to canola, but we saw no evidence that infection treatment shifted foraging preferences. Although high-infection flowering strips increased colony infection intensity, colony reproduction was improved with any flowering strips compared to canola alone. Effects of flowering strips on colony reproduction were explained by nectar availability, but effects of flowering strips on infection intensity were not. Thus, flowering strips benefited colony reproduction by adding floral resources, but certain plant species also come with a risk of increased pathogen infection intensity. [ABSTRACT FROM AUTHOR]

Population declines of pollinators constitute a major concern for the fate of biodiversity and associated ecosystem services in a context of global change. Massive declines of pollinator populations driven by habitat loss, pollution, and climate change have been reported, whose consequences at community and ecosystem levels remain elusive. We conducted a mathematical modeling and computer simulation study to assess the dynamic consequences of pollinator declines for the biodiversity of plants and pollinators. Specifically, we evaluated the effects of increased mortality and decreased carrying capacity of specialist vs. generalist and effective vs. ineffective pollinators visiting specialist vs. generalist plants on long-term community biomass and species persistence. Our results reveal that increased larval mortality and increased competition for space among larvae had the greatest impacts on the decline of pollinator diversity. In contrast, the largest sustained decreases in pollinator biomass were driven by increased adult mortality in spite of a small increase in pollinator species persistence. Decreased pollinator diversity led in turn to decreased plant diversity. Attacking pollinators with high degree and connected mostly to low-degree plants produced the greatest losses of plant diversity. Pollinator effectiveness had no noticeable effect on persistence. Our results illuminate our understanding of the consequences of pollinator declines for the maintenance of biodiversity. [ABSTRACT FROM AUTHOR]

Socio-cultural research might address anthropocentric reasons for honeybee (Apis mellifera) conservation. In some regions, particular honeybee subspecies are considered to be native; A. mellifera mellifera (“dark bee”) in the north-east and A. mellifera carnica in the Island Beskids in Poland. Additionally, A. mellifera caucasia (often incorrectly called A. mellifera caucasica) and Buckfast are reported across Poland. In order to verify the actual choice of beekeepers, a survey on honeybee subspecies kept in apiaries was conducted annually from 1980 to 2018. This is a way to verify if conservation management towards the dark bee influenced its maintenance at a sufficient level for their restoration. The analysis revealed that Polish beekeepers know what is “buzzing” in their hives, and the awareness of which subspecies/types of honeybee they maintain has grown through the years. Initially, they kept up to four different subspecies per apiary, but now most have only one (maximum of two). Currently, Polish apiaries approach a homogeneous share with the exclusive presence of A. mellifera carnica subspecies. The popularity of indigenous A. mellifera mellifera has declined over time and is low now. It seems that new solutions should be considered to increase the effectiveness of dark European bee conservation management efforts.

Pathogens are one of the factors driving pollinator declines. Diet can play an important role in mediating pollinator health and resistance to pathogens. Sunflower pollen (Helianthus annuus) dramatically reduced a gut pathogen (Crithidia bombi) of Bombus impatiens previously, but the breadth of this effect was unknown. We tested whether pollen from nine H. annuus cultivars, four wild H. annuus populations, H. petiolarus, H. argophyllus and two Solidago spp., reduced Crithidia in B. impatiens compared to mixed wildflower pollen and buckwheat pollen (Fagopyrum esculentum) as controls. We also compared hand- and honeybee-collected pollen (which contains nectar) to assess whether diet effects on pathogens were due to pollen or nectar. All Helianthus and Solidago pollen reduced Crithidia by 20–40-fold compared to buckwheat pollen, and all but three taxa reduced Crithidia compared to wildflower pollen. We found no consistent differences between hand- and bee-collected pollen, suggesting that pollen alone can reduce Crithidia infection. Our results indicate an important role of pollen diet for bee health and potentially broad options within the Asteraceae for pollinator plantings to manage bee disease.

Greater pollination intensity can enhance maternal plant fitness by increasing seed set and seed quality as a result of more intense pollen competition or enhanced genetic sampling. We tested experimentally these effects by varying the pollen load from a single pollen donor on stigmas of female flowers of Dalechampia scandens (Euphorbiaceae) and measuring the effects on seed number and seed mass. Seed set increased rapidly with pollen number at low to moderate pollen loads, and a maximum set of three seeds occurred with a mean pollen load of 19 pollen grains. We did not detect a trade‐off between the number of seeds and seed mass within a fruit. Seed mass increased with increasing pollen load, supporting the hypothesis of enhanced seed quality via increased pollen‐competition intensity or genetic sampling. These results suggest that maternal fitness increases with larger pollen loads, even when the fertilization success is already high. Our results further highlight the importance of high rates of pollen arrival onto stigmas, as mediated by reliable pollinators. Comparing the pollen‐to‐seed response curve obtained in this experiment with those observed in natural populations suggests that pollen limitation may be more severe in natural populations than predicted from greenhouse studies. These results also indicate that declines in pollinator abundance may decrease plant fitness through lowered seed quality before an effect on seed set is detected. [ABSTRACT FROM AUTHOR]

Summary: A widely observed pollinator decline around the world has led to the prediction that terrestrial ecosystems could be disrupted as plant pollination suffers, but declining pollination success has not been tested rigorously in wild plants, and it still remains unclear how pollination success of plant species responds differently in the context of pollinator decline.By viewing the number of seeds per pod as a quantitative measure of successful pollination, we examined seed pods in 4637 herbarium specimens of 109 obligately outcrossing legumes collected over the past century.We found that only 13 species showed significant temporal change with nine of those as an increase. None of the three subfamilies of legumes showed a consistent trend, and the subfamily Papilionoideae with the most specialized flowers, had increasing seed number per pod more often than decreasing.We conclude that legume pollination in China shows no sign of disruption and the effects of plant–pollinator disruption may be more complicated than simplistic predictions have allowed. [ABSTRACT FROM AUTHOR]

Summary: Widespread reports of declining populations of pollinators have raised concerns that plant populations may be incurring increasing shortfalls in pollination, but few studies have measured pollination deficits over enough seasons to detect such changes. I have conducted pollen‐supplementation experiments in a wild population of the glacier lily (Erythronium grandiflorum, Liliaceae) from 1993 to 2018.Pollination deficits were estimated by comparing the fruit set of hand‐pollinated, single‐flowered plants to that of open‐pollinated controls. For a subset of years, seed set data were also available.A previous publication reported a significant deterioration of pollination in this population from 1993 to 2009, and suggested phenological dislocation as a possible cause. That deterioration is no longer evident in the longer‐term data set.Very long time series may be necessary to detect temporal trends in pollination service. This population consistently experiences stronger pollination deficits before its flowering peak than after. This heterogeneity suggests caution in characterizing a population as pollination‐limited or not, even within a single season. [ABSTRACT FROM AUTHOR]

Background and Aims To predict the evolutionary consequences of pollinator declines, we need to understand the evolution of delayed autonomous self-pollination, which is expected to evolve as a mechanism of reproductive assurance when cross-pollination becomes unreliable. This involves estimating the costs of increased levels of selfing as well as those associated with floral senescence. Methods We studied the mechanisms and costs of delayed self-pollination in the mixed-mating vine Dalechampia scandens (Euphorbiaceae) by first assessing among-population variation in herkogamy and dichogamy, which together determine the rate and timing of autonomous self-pollination. We then tested whether floral longevity responds plastically to delayed pollination. Finally, we assessed the costs of delayed self-pollination in terms of seed number and size, explicitly separating inbreeding depression from effects of floral senescence. Key Results Herkogamy varied extensively, while variation in dichogamy was more limited. Unpollinated blossoms increased their longevity, but seed quantity and quality decreased with increasing delays in pollination, independently of inbreeding depression. Conclusions In D. scandens , earlier autonomous selfing is facilitated by reduced herkogamy rather than reduced protogyny, providing reproductive assurance while maintaining the possibility for outcrossing events. Effective early autonomous self-pollination may evolve under reduced cross-pollination reliability in response to costs associated with floral senescence. [ABSTRACT FROM AUTHOR]

Summary: In the event of a community turnover, population decline, or complete disappearance of pollinators, animal‐pollinated plants may respond by adapting to novel pollinators or by changing their mating system. The ability of populations to adapt is determined by their ability to respond to novel selection pressures, i.e. their evolvability. In the short term, evolvability is determined by standing genetic variation in the trait under selection.To evaluate the evolutionary potential of plant reproductive systems, I compiled genetic‐variance estimates for a large selection of floral traits mediating shifts in pollination and mating systems. Then, I computed evolvabilities and compared these among trait groups and against the evolvabilities of vegetative traits.Evolvabilities of most floral traits were substantial yet tended to be lower than the median for vegetative traits. Among floral traits, herkogamy (anther–stigma distance), floral‐display traits and perhaps floral‐volatile concentrations had greater‐than‐average evolvabilities, while the evolvabilities of pollinator‐fit traits were below average.These results suggest that most floral traits have the potential to evolve rapidly in response to novel selection pressures, providing resilience of plant reproductive systems in the event of changing pollinator communities. [ABSTRACT FROM AUTHOR]

Pollinators are on the decline and loss of flower resources play a major role. This raises concerns regarding production of insect-pollinated crops and therefore food security. There is urgency to mitigate the decline through creation of farming systems that encourage flower-rich habitats. Cowpea is a crop that produces pollen and nectar attractive to pollinators. Twenty-four cowpea varieties were planted, and the number of pollinators were counted using three sampling methods: pan traps, sticky traps, and direct visual counts. Five pollinator types (honey bees, bumble bees, carpenter bees, wasps, and butterflies and moths), 11 and 16 pollinator families were recorded from direct visual counts, pan and sticky traps, respectively. Pollinator distribution varied significantly among varieties and sampling methods, with highest number on Penny Rile (546.0 ± 38.6) and lowest (214.8 ± 29.2) in Iron and Clay. Sticky traps accounted for 45%, direct visual counts (31%), and pan traps (23%) of pollinators. Pollinators captured by pan traps were more diverse than the other methods. The relationship between number of pollinators and number of flowers was significant (r2 = 0.3; p = 0.009). Cowpea can increase resources for pollinators and could be used to improve pollinator abundance and diversity in different farming systems.

Since pollination by insects is vitally important for much of global crop production, and to provide pollination services more widely throughout the planetary ecosystems, the prospect of an imminent 'pollination crisis', due to a die-off of flying insects, is most disquieting, to say the least. Indeed, the term 'ecological Armageddon' has been used in the media. However, to know whether or not a wholesale decline in flying pollinators (including non-bee species) is occurring across the world is very difficult, due to an insufficiency of geographically widespread and long-term data. Bees, as the best documented species, can be seen to be suffering from chronic exposure to a range of stressors, which include: a loss of abundance and diversity of flowers, and a decline in suitable habitat for them to build nests; long-term exposure to agrochemicals, including pesticides such as neonicotinoids; and infection by parasites and pathogens, many inadvertently spread by the actions of humans. It is likely that climate change may impact further on particular pollinators, for example bumble bees, which are cool-climate specialists. Moreover, the co-operative element of various different stress factors should be noted; thus, for example, exposure to pesticides is known to diminish detoxification mechanisms and also immune responses, hence lowering the resistance of bees to parasitic infections. It is further conspicuous that for those wild non-bee insects - principally moths and butterflies - where data are available, the picture is also one of significant population losses. Alarmingly, a recent study in Germany indicated that a decline in the biomass of flying insects had occurred by 76% in less than three decades, as sampled in nature reserves across the country. Accordingly, to fully answer the question posed in the title of this article 'pollinator decline - an ecological calamity in the making?' will require many more detailed, more geographically encompassing, more species-inclusive, and longer-term studies, but the available evidence points to a clear 'probably', and the precautionary principle would suggest this is not a prospect we can afford to ignore. [ABSTRACT FROM AUTHOR]

Phytochemicals produced by plants, including at flowers, function in protection against plant diseases, and have a long history of use against trypanosomatid infection. Floral nectar and pollen, the sole food sources for many species of insect pollinators, contain phytochemicals that have been shown to reduce trypanosomatid infection in bumble and honey bees when fed as isolated compounds. Nectar and pollen, however, consist of phytochemical mixtures, which can have greater antimicrobial activity than do single compounds. This study tested the hypothesis that pollen extracts would inhibit parasite growth. Extracts of six different pollens were tested for direct inhibitory activity against cell cultures of the bumble bee trypanosomatid gut parasite Crithidia bombi. Surprisingly, pollen extracts increased parasite growth rather than inhibiting it. Pollen extracts contained high concentrations of sugars, mainly the monosaccharides glucose and fructose. Experimental manipulations of growth media showed that supplemental monosaccharides (glucose and fructose) increased maximum cell density, while a common floral phytochemical (caffeic acid) with inhibitory activity against other trypanosomatids had only weak inhibitory effects on Crithidia bombi. These results indicate that, although pollen is essential for bees and other pollinators, pollen may promote growth of intestinal parasites that are uninhibited by pollen phytochemicals and, as a result, can benefit from the nutrients that pollen provides.

Honey bees forage across a large area, continually scouting the local landscape for ephemeral food resources. Beekeepers often rely on flowering plants in and around irrigated farmland to maintain their colonies during dry seasons, despite the potential risk of pesticide exposure. Recent declines in pollinator abundance and diversity have focused attention on the role of pesticides and their effects on honey bee health. This investigation examined two types of landscapes within a two-mile (3.2 km) radius of honey bee colonies: an intensive agricultural setting and a rural setting without intensive agriculture. More than 10,000 acres of agricultural land was surveyed to quantify the area of cultivated crops and the area treated with pesticides, including seed treatments and foliar applications of insecticides. Samples of honey, bee bread (stored pollen), beeswax, and adult bees were collected from hives in both landscape types and screened for pesticide residues to determine if foraging bees were transporting pesticides to hives. Some samples of bee bread and honey did contain pesticide residues, but these were below known lethal dose (LD50) levels for honey bees. Beeswax samples contained the highest levels of contamination, but most were still relatively low. Samples were screened for 174 common agricultural pesticides and metabolites, but only 26 compounds were detected during the two-year study. These included one defoliant, one insect growth regulator, five herbicides, six fungicides, six insecticides never used in beekeeping, and five insecticides/miticides and their metabolites, which are used in beekeeping and for various other agricultural purposes, as well as two miticides exclusively used by beekeepers to control Varroa destructor. Bee colonies foraging in agricultural landscapes are potentially exposed to numerous pesticide applications. While the residues detected in this study did not pose an acute lethal risk to adult honey bees, this study did not measure sublethal effects on bee colony health or performance, which merit further investigation.