Pollinator Loss Research Articles

Traditional semi-natural grassland management with heterogeneous mowing times enhances flower resources for pollinators in agricultural landscapes

For a diverse pollinator fauna it is important that pollen and nectar are available over the entire summer at spatially relevant scales. Semi-natural hay meadows are among the most important sources of flower resources for pollinators, but the resources are strongly affected by the timing of mowing. Management recommendations for hay meadows often prescribe late mowing on order to allow undisturbed flowering during most of the summer. Traditional practices, however, often include also earlier mowing. We investigate the link between the temporal variation of flower resources and traditional mowing practices of semi-natural hay meadows in a low-intensity agricultural landscape in Romania. In early August, we botanically surveyed meadows that were cut early, intermediately, or late in the season. We recorded all herb species, their phenological stage, and the number of reproductive units of each species. Data were analysed using DCA, LM and GLM. Plant species richness and composition are not affected by the time of mowing, but different sets of species flower in semi-natural grasslands with different mowing regimes. In August the proportion of species flowering and flower density are highest in the early-mown meadows due to re-flowering after mowing. Analyses of phenological stages indicate that late-mown meadows are the main pollen and nectar sources in July, whereas meadows mown early are the main resource from August to the end of the season. The results demonstrate that for pollinator conservation, heterogeneous mowing times within a landscape need to be encouraged when possible, and that strict focus on late mowing may lead to shortage of flower resources late in the summer. Studies of low-intensity agriculture has a great potential for learning about management methods that can be used in other parts of the world where traditional practices have been lost. Such studies can thereby contribute with important knowledge to manage global pollinator loss.

Geographic mosaic theory of coevolution in plant and pollinator interaction: Process, evidence, prospect

Coevolution refers to evolutionary changes in the traits of two or more interacting species caused by reciprocal natural selection. Geographic mosaic theory of coevolution (GMC) proposes that the dynamics of coevolution between pairs or group of species often occur at different geographic scales. There are three hypotheses on the coevolutionary process. (1) Different evolutionary interaction trajectories among populations are likely to generate a selection mosaic. (2) A mixture of coevolutionary hotspots and coldspots. Hot spots are the subset of communities in which much of the coevolutionary change occurs and coldspots refer to areas where coevolutionary selection hardly occurs or completely does not occur. (3) There is a continual population remixing of the range of coevolving traits, resulting from the selection mosaic, coevolutionary hotspots, gene flow, random genetic drift, and local extinction of subpopulations. Studies of GMC between plants and pollinators indicate that shifts of effective pollinators among different geographic populations may cause divergence in floral traits (i.e., pollination ecotype). Changes of pollinator assemblages or species components have been illustrated coevolving with floral morphology or reward among populations from different altitudes or habitats. Here, recent case studies of GMC between plants and pollinators are grouped into five categories: Floral morphology and pollinator components, corolla tube/nectar spur and pollinator feeding structure, floral color, floral scents, floral rewards and pollinator assemblages. Floral tube or nectar spur length is positively related to pollinator body structures, such as the proboscis and leg length. The adaptation of flower color and pollinator vision provides a series of examples for the GMC. With the increase of altitude, flower color changed from blue and ultraviolet blue adapted to bee vision to blue-green and green adapted to fly vision. Recent study indicated that the difference in cycad odor components related to a shift of beetle species in different regions, suggesting a potential coevolutionary relationship between flower odor and pollinators. Studies showed that where bees foraged more nectar, flowers secreted more nectar, suggesting that floral reward amounts and types coevolve with pollinators among different geographic populations. An examination of GMC in plant-pollinator interactions involves three steps in general: (1) Detection of the relationship between floral traits and pollinator shift or body structure. (2) Transplanting experiments to detect differences in seed set between native phenotypes and transplanted phenotypes. (3) Single pollinator visit experiment to detect pollen output differences between native and transplanted phenotypes. Experimental evolutionary biology not only can test whether floral variation is related to pollinator shifts, but also make people aware of the impact of the reduction or loss of pollinators on the evolutionary consequences. To illustrate GMC between plants and pollinators, it is essential to isolate the evolutionary changes in traits caused by biotic factors or abiotic factors in future. It would be highly appreciated if genome scans and analysis are used in further studies to explore the genome-wide patterns of GMC between plants and pollinators.

A Flower-Specific Phospholipase D Is a Stigmatic Compatibility Factor Targeted by the Self-Incompatibility Response in Brassica napus

Self-incompatibility (SI) is a genetic mechanism in hermaphroditic flowers that prevents inbreeding byrejection of self-pollen, while allowing cross- or genetically diverse pollen to germinate on the stigma to successfully fertilize the ovules. In Brassica, SI is initiated by the allele-specific recognition of pollen-encoded, secreted ligand (SCR/SP11) by the stigmatic receptor kinase S-locus receptor kinase (SRK), resulting in activation of SRK through phosphorylation [1-3]. Once activated, this phospho-relay converges on intracellular compatibility factors, which are immediately targeted for degradation by the E3 ligase, ARC1, resulting in the pollen rejection response [4, 5]. Through proteomics approach using proteins from SI activated stigmas of Brassica napus, we identified phospholipase D α1 (PLDα1) as one of the candidates that is most likely targeted for degradation after SI [6]. PLDα1 is enriched in the stigmas and functions as a stigmatic compatibility factor as loss of PLDα1 compromised compatible pollination, while overexpression of PLDα1 in self-incompatible stigmas led to breakdown of SI response. PLDα1 can be ubiquitinated by ARC1 and accumulate in ARC1-suppressed lines, confirming PLDα1 as a target of ARC1 during SI response. Addition of phosphatidic acid (PA) to PLDα1-deficient stigmas was sufficient to rescue compatibility, suggesting an essential role for PA generated by PLDα1 for compatible interactions. We propose that PA produced by PLDα1 activity during compatible pollination promotes vesicle fusion at the membrane to facilitate exocytosis necessary for pollen germination to occur, while SI response could abrogate this process by targeting PLDα1 for degradation.

Converting arable land into flowering fields changes functional and phylogenetic community structure in ground beetles

Agri-environmental schemes aim to promote biodiversity in agricultural landscapes. However, knowledge about the impact of these measures on diversity components beyond species richness, especially for non-target species and their ecological functions, is still very poor. Here, we investigated the response of ground beetle communities to the conversion of arable land into flowering fields, which are primarily installed to counteract pollinator loss in agricultural landscapes. We are focusing on the relationship between biodiversity components and the evolutionary relationship among functional groups.Land-use conversion from arable land to flowering fields has changed the phylogenetic community composition of ground beetles towards a phylogenetically clustered community. This is due to an increase in closely related medium-sized herbivorous species and a decrease in evolutionarily distinct small carnivorous species. Phylogenetic clustering did not result in a reduction of functional richness, but it increased the number of unique trait combinations of species within the local communities. This suggests a low ecological redundancy among herbivorous species. Because species richness, functional richness and phylogenetic diversity were unaffected by conversion, phylogenetic community structuring was predominantly driven by species turnover rather than by numerical changes.Flowering fields can act as refuges for herbivorous carabids that potentially affect the surrounding agricultural landscape by providing important ecosystem services such as weed control. To understand the impact of habitat transformation on carabid biodiversity, it was more informative to relate response traits to phylogenic and functional diversity than to use single diversity measures such as species richness. This conclusion might also apply to many other taxa.

Chronic exposure of bumblebees to neonicotinoid imidacloprid suppresses the entire mevalonate pathway and fatty acid synthesis

Determining the side effects of pesticides on pollinators is an important topic due to the increasing loss of pollinators. We aimed to determine the effects of chronic sublethal exposure of the neonicotinoid pesticide imidacloprid on the bumblebee Bombus terrestris under laboratory conditions. The analytical standard of imidacloprid in sugar solution was used for the treatment. Verification of pesticides using UHPLC-QqQ-MS/MS in the experimental bumblebees showed the presence of only two compounds, imidacloprid and imidacloprid-olefin, which were found in quantities of 0.57 ± 0.22 and 1.95 ± 0.43 ng/g, respectively. Thus, the level of the dangerous metabolite imidacloprid-olefin was 3.4-fold higher than that of imidacloprid. Label-free nanoLC-MS/MS quantitative proteomics of bumblebee heads enabled quantitative comparison of 2883 proteins, and 206 proteins were significantly influenced by the imidacloprid treatment. The next analysis revealed that the highly downregulated markers are members of the terpenoid backbone biosynthesis pathway (KEGG: bter00900) and that imidacloprid treatment suppressed the entire mevalonate pathway, fatty acid synthesis and associated markers. The proteomics results indicate that the consequences of imidacloprid treatment are complex, and the marker changes are associated with metabolic and neurological diseases and olfaction disruption. This study provides important markers and can help to explain the widely held assumptions from biological observations. SignificanceThe major finding is that all markers of the mevalonate pathway were substantially downregulated due to the chronic imidacloprid exposure. The disbalance of mevalonate pathway has many important consequences. We suggest the mechanism associated with the novel toxicogenic effect of imidacloprid. The results are helpful to explain that imidacloprid impairs the cognitive functions and possesses the delayed and time cumulative effect.

Flower strip networks offer promising long term effects on pollinator species richness in intensively cultivated agricultural areas

BackgroundIntensively cultivated agricultural landscapes often suffer from substantial pollinator losses, which may be leading to decreasing pollination services for crops and wild flowering plants. Conservation measures that are easy to implement and accepted by farmers are needed to halt a further loss of pollinators in large areas under intensive agricultural management. Here we report the results of a replicated long-term study involving networks of mostly perennial flower strips covering 10% of a conventionally managed agricultural landscape in southwestern Germany.ResultsWe demonstrate the considerable success of these measures for wild bee and butterfly species richness over an observation period of 5 years. Overall species richness of bees and butterflies but also the numbers of specialist bee species clearly increased in the ecological enhancement areas as compared to the control areas without ecological enhancement measures. A three to five-fold increase in species richness was found after more than 2 years of enhancement of the areas with flower strips. Oligolectic bee species increased significantly only after the third year.ConclusionsIn our long-term field experiment we used a large variety of seed mixtures and temporal variation in seeding time, ensured continuity of the flower-strips by using perennial seed mixtures and distributed the measures over c. 10% of the landscape. This led to an increase in pollinator abundance, suggesting that these measures may be instrumental for the successful support of pollinators. These measures may ensure the availability of a network of diverse habitats and foraging resources for pollinators throughout the year, as well as nesting sites for many species. The measures are applied in-field and are suitable for application in areas under intensive agriculture. We propose that flower strip networks should be implemented much more in the upcoming CAP (common agricultural policy) reform in the European Union and promoted more by advisory services for farmers.

Las razones de por qué Chile debe detener la importación del abejorro comercial Bombus terrestris (Linnaeus) y comenzar a controlarlo

The global pollination crisis is not only produced by loss of pollinators but also by their homogenization, both processes caused by humans. This crisis impacts the persistence of many native plants species worldwide. In this document we analyze the ecological impacts that warrant the prohibition of new income of commercial bumblebee, Bombus terrestris to Chile. This species is highly invasive, it has been banned in other countries, but in Chile its entry is allowed since 1997. Thousands of colonies and fertilized queens entered the country every year and expand throughout the rest of South America. We give eleven reasons to stop B. terrestris entry to Chile and start controlling it. We justify these reasons based on work done both in the country and outside of it. At the same time, through the conclusions, we mentioned what should be the steps to followed regarding the prohibition B. terrestris entry to Chile.

Effects of cage volume and bee density on survival and nutrient intake of honeybees (Apis mellifera L.) under laboratory conditions

Laboratory experiments are vital to exploring the causes of pollinator loss, but for these experiments to be informative, they should attempt to replicate the hive environment and conserve social interactions. It is unclear how honeybee density and group size affect survival and behaviour in the laboratory. We manipulated cage volume (125–1312 ml) and honeybee group size (10–180 bees) and tested the effects on survival and feeding behaviour. Bees were allowed to regulate their intake from two liquid diets with dry ingredient protein: carbohydrate (P:C) ratios of 0:1 and 1:50 (w/w). Intake was consistent across cages, showing that feeding behaviour is largely unaffected by cage conditions. High survival was recorded in cages with a volume of 2.08 ml/bee, which falls within the natural range of 1.9–3.8 ml/bee in nest sites, and in groups of < 60 bees. We suggest that cage volume is more important than group size, and that cage dimensions should be adjusted so that each bee has < 3.0 ml of space.

Synergistic effects of pathogen and pesticide exposure on honey bee (Apis mellifera) survival and immunity.

Declines in native insect pollinator populations and substantial losses in managed honey bees have been reported on a global scale and become a widespread concern because of the importance of these insects for human food production and ecosystem stability. Several potential factors have been studied as possible causes of declining pollinator health, such as parasites and pathogens, exposure to agricultural pesticides, habitat loss and/or climate change. More recently, a combination of these factors rather than a single cause have been blamed for observed pollinator losses, but field studies of such interactions are challenging, especially in the presence of confounding environmental stressors. We therefore examined the impact of single and combined stressors on the honey bee (Apis mellifera) in a generally healthy Australian population. We exposed workers during their larval development and drones until they reached sexual maturity to the neonicotinoid pesticide Thiamethoxam, at concentrations more than 20 times lower than we initially measured in the field, the microsporidian gut pathogen Nosema apis or both stressors at the same time. We found that simultaneous exposure significantly reduced bee health. We observed a substantial increase in mortality and a reduction of immunocompetence in workers exposed to both the pathogen and the pesticide. We conclude that the exposure of generally healthy bees to multiple environmental stressors results in synergistic effects where the effects are expected to negatively impact performance and could be sufficient to trigger colony collapse. We found that the vast majority of males did not survive to sexual maturity after exposure to very low levels of Thiamethoxam. This would not only reduce the reproductive success of individual colonies, but can also impact gene flow and genetic diversity at the population level, which are both known as key components of honey bee health.

Effects of long‐term variation in pollinator abundance and diversity on reproduction of a generalist plant

Abstract Quantifying the benefits of pollinator abundance and diversity for plant reproduction is a critical challenge, especially given recent pollinator declines. Many studies test for pollen limitation (PL), but huge gaps remain in our understanding of how often and why plants experience PL. Most studies are limited to a few sites or years. Little existing research mechanistically links pollinator visitation with plant reproduction. Also, buffering against variability in visitation is a key but largely untested potential benefit of pollinator diversity. Long‐term studies pairing visitation data with PL experiments are essential to addressing these gaps, but extremely rare. I measured pollinator visitation, responses to pollen supplementation, and fruit weights in the generalist plant Scrophularia californica across multiple sites for 8 years. I determined how often S. californica experienced significant PL and tested mechanistic models predicting PL and fruit (capsule) weight from visitation. I then used those models to simulate pollinator loss and evaluate the relative effects of changes in visit quantity and quality. I explored the stabilizing benefits of visitor diversity by quantifying both covariation among pollinators and effects of simulated species loss on variation in PL and capsule weights. Scrophularia showed significant PL in only 26.9% of patch/year combinations tested. Visitation by the most abundant (Apis mellifera) and effective (Vespula pensylvanica) pollinators strongly predicted PL and capsule weights. Both response curves were highly nonlinear, but PL saturated more with increased visitation. Pollinator loss simulations predicted substantially increased PL and reduced capsule weights, mostly because of lower visit numbers rather than changes in visit quality. Visitation rates of individual pollinators varied substantially and without correlation. Simulated pollinator loss increased the spatial and temporal skew in visitation, resulting in higher predicted coefficients of variation for PL and capsule weights. Synthesis. Previous work predicts a nonlinear relationship between pollinator visitation and plant reproduction, but this is the first long‐term study I am aware of that quantifies such a pattern. The analysis of covariance in pollinator visitation combined with my simulation results provide novel empirical support for another important hypothesis, that multiple pollinators can provide stabilizing benefits for plant reproduction.

Low dose of neonicotinoid insecticide reduces foraging motivation of bumblebees.

Widespread use of neonicotinoid insecticides, such as imidacloprid, is often associated with diminishing populations of bees; this loss of pollinators presents a concern for food security and may cause unpredictable changes in ecological networks. However, little is known about the potential behavioural mechanisms behind the neonicotinoid-associated pollinator decline. We quantified the effects of low-dose (1 ppb) imidacloprid exposure on the foraging behaviour of bumblebees (Bombus terrestris). Individual bumblebees were released into a flight arena containing three patches of robotic flowers whose colour (yellow, orange, blue) indicated whether the flower delivered a reward (sugar solution). Exposure to imidacloprid had no significant effect on measures of bumblebee physical performance (such as flight speed) or learning (identifying rewarding flowers). However, pesticide-treated bumblebees had reduced foraging motivation compared with the control bumblebees, as they visited fewer robotic flowers, were slower to start foraging and did not visit all three flower colours as often. Neonicotinoid concentrations of 1 ppb, often reported in plant nectar near agricultural lands, can thus affect the foraging behaviour of bumblebees. Even without a notable impact on flight performance and learning, a reduction in foraging motivation could explain the poor performance of colonies of bumblebees exposed to neonicotinoids.

The intertwined effects of natural vegetation, local flower community, and pollinator diversity on the production of almond trees

Wild pollinators are a valuable natural resource for crops, as they often increase their production and quality. For this reason, there is currently a great interest in the development of management and conservation tools that help to maintain a wide variety of wild pollinators in agro-systems. To achieve this, it becomes a priority to study the diversity of wild pollinators in relevant crops as well as the local and landscape characteristics that benefit them. The almond tree (Prunus dulcis) is a crop of high economic interest, with a large dependence on pollinators due to the self-incompatibility of most of its varieties and, thus, it is very vulnerable to pollinator losses. By using field data and habitat characterization of 18 almond fields in Mallorca Island (Spain), we assessed how the abundance and diversity of pollinators varied with local and landscape characteristics (at 1 and 2 km buffer zones) of the fields, and how those affected almond production (fruit set). Almond trees were mostly pollinated by honeybees, but they were also visited by a large number of wild pollinators. The percentage of natural area in the 2 km buffer zones increased both pollinator-species richness and honeybee visits. At the field level, the flower community in the ground positively influenced almond production, both directly and indirectly by increasing the diversity of wild pollinators. Pollinator-species diversity directly increased fruit production but was negatively affected by honeybee abundance, which suggests that a high density of honeybees might result in negative effects on almond production through competition with wild pollinators. Management strategies to improve almond production might include favoring wild pollinators through the maintenance of natural habitats surrounding crop fields, and preserving the flowering herb community that occurs spontaneously in the groundcover of almond fields in Mediterranean areas.

Scaling up effects of measures mitigating pollinator loss from local‐ to landscape‐level population responses

Abstract Declining pollinator populations have caused concern about consequences for food production, and have initiated an increasing number of initiatives that aim to mitigate pollinator loss through enhancement of floral resources. Studies evaluating effects of mitigation measures generally demonstrate positive responses of pollinators to floral resource enhancement. However, it remains unclear whether this represents landscape‐level population effects or results from a spatial redistribution of individuals from otherwise unaffected populations. Here, we present a method for estimating landscape‐level population effects using data from commonly used standardized pollinator transect surveys. The approach links local density responses of pollinators in both mitigation sites and surrounding landscape elements to the area these habitats occupy in mitigation landscapes as well as control landscapes to obtain landscape‐level population estimates. We demonstrate the method using data from a 2‐year study examining the effects of experimental wildflower enhancements on wild bumblebees and solitary bees in Dutch agricultural landscapes. The results show that conclusions based on local responses may differ significantly from those based on landscape‐level responses. Wildflower enhancements significantly enhanced landscape‐level abundance of both bumblebees and solitary bees. Bumblebees showed a pronounced positive local density response in mitigation sites and the surrounding landscape that was in line with significant landscape‐level increases in abundance. However, solitary bees showed no local response to mitigation sites, and the landscape‐level increases in abundance only became apparent when the area of bee habitat was taken into account. Incorporating the area of both newly created and pre‐existing pollinator habitats into effect estimates accounts for density‐dependent processes such as dilution, spillover and local concentration of individuals. It, therefore, results in more reliable estimates of the response to mitigation measures of pollinators, as well as other mobile arthropod groups that are often being surveyed using transect surveys.

Field Populations of Wild Apis cerana Honey Bees Exhibit Increased Genetic Diversity Under Pesticide Stress Along an Agricultural Intensification Gradient in Eastern India.

Pesticides have been reported to be one of the major drivers in the global pollinator losses. The large-scale decline in honey bees, an important pollinator group, has resulted in comprehensive studies on honey bee colonies. Lack of information on native wild pollinators has paved the way for this study, which highlights the underlying evolutionary changes occurring in the wild honey bee populations exposed to pesticides along an agricultural intensification landscape. The study reports an increased genetic diversity in native Apis cerana Fabricius (Hymenoptera: Apidae) populations continually exposed to pesticide stress. An increased heterozygosity, evidenced by a higher electrophoretic banding pattern, was observed in the pesticide-exposed populations for two isozymes involved with xenobiotic metabolism—esterase and glucose-6-phosphate dehydrogenase. Differential banding patterns also revealed a higher percentage of polymorphic loci, number of polymorphic bands, Nei’s genetic distance, etc. observed in these populations in the Randomly Amplified Polymorphic DNA–Polymerase Chain Reaction (RAPD–PCR) experiments using three random decamer primers. Higher heterozygosity, being indicative of a more resistant population, implies population survival within the threshold pesticide stress. This study reports such changes for the first time in native wild Indian honey bee populations exposed to pesticides and has far-reaching implications on the population adaptability under pesticide stress.

Exotic flies maintain pollination services as native pollinators decline with agricultural expansion

Abstract Globally, conversion of natural habitat to agricultural land is a primary driver of declines in critical ecosystem services, including pollination. However, exotic species are often well‐adapted to human‐modified environments and could compensate for ecosystem services that are lost when native species decline. We measured pollination services (pollen delivery to stigma) provided by wild insects to a mass flowering crop, pak choi Brassica rapa at 12 sites across a gradient of increasing agricultural land use (agricultural expansion) in New Zealand. We found that pollination services increased as the proportion of agricultural land in the surrounding landscape increased; pollination from exotic species exceeded the loss of pollination from native species. However, pollination service delivery became increasingly dominated by a few exotic fly species that were active throughout the day, compared to native species, which had more constrained activity patterns. Synthesis and applications. The best way to ensure continued sufficient crop pollination is to protect and restore diverse natural habitats on or around farms, as species‐rich pollinator communities are relatively resilient to further environmental change. However, we show that where human‐driven disturbance has caused loss of native pollinator species, exotic pollinators can maintain sufficient pollination. Therefore, in areas where native species loss cannot easily be reversed, decisions about pesticide use and habitat provision that foster populations of beneficial exotic species are likely to maintain pollination service delivery, at least in the short term. This highlights the need for land managers to identify the pollinator communities that are present on their farms, whether native or exotic, and make decisions to support these important communities accordingly.

Global importance of vertebrate pollinators for plant reproductive success: a meta‐analysis

Vertebrate pollinators are increasingly threatened worldwide, but little is known about the potential consequences of declining pollinator populations on plants and ecosystems. Here, we present the first global assessment of the importance of vertebrate pollinators in the reproductive success of selected flowering plants. Our meta‐analysis of 126 experiments on animal‐pollinated plants revealed that excluding vertebrate pollinators – but not insect pollinators – reduced fruit and/or seed production by 63% on average. We found bat‐pollinated plants to be more dependent on their respective vertebrate pollinators than bird‐pollinated plants (an average 83% reduction in fruit/seed production when bats were excluded, as compared to a 46% reduction when birds were excluded). Plant dependence on vertebrate pollinators for fruit/seed production was greater in the tropics than at higher latitudes. Given the potential for substantial negative impacts associated with the loss of vertebrate pollinators, there is a clear need for prompt, effective conservation action for threatened flower‐visiting vertebrate species. Additional research on how such changes might affect wider ecosystems is also required.

A Flower-Specific Phospholipase D1 is a Stigmatic Compatibility Factor Targeted by the Self-Incompatibility Response in Brassica Napus

Self-incompatibility (SI) is a genetic mechanism in hermaphroditic flowers that prevents inbreeding by rejection of self-pollen, while allowing cross or genetically diverse pollen to germinate on the stigma to successfully fertilize the ovules. In Brassica, SI is initiated by the allele-specific recognition of pollen-encoded, secreted ligand (SCR/SP11) by the stigmatic receptor kinase S-locus receptor kinase (SRK), resulting in activation of SRK through phosphorylation. Once activated, this phospho-relay converges on intracellular compatibility factors, which are immediately targeted for degradation by the E3 ligase, ARC1, resulting in the pollen rejection response. Through proteomics approach using proteins from SI activated stigmas of canola (Brassica napus), we identified phospholipase D1 (PLD1) as one of the candidates that is likely targeted for degradation following SI. PLD1 is enriched in the stigmas and functions as a stigmatic compatibility factor as loss of PLD1 compromised compatible pollination, while overexpression of PLD1 in self-incompatible stigmas led to breakdown of SI response. PLD1 overexpression was also associated with enhanced membrane activity following SI pollination, mimicking compatible pollination. PLD1 can be ubiquitinated by ARC1 and accumulate in ARC1- suppressed lines confirming PLD1 as a direct target of ARC1 during SI response. Addition of phosphatidic acid (PA) to PLD1 deficient stigmas was sufficient to rescue compatibility suggesting an essential role for PA generated by PLD1 for compatible interactions. We propose that PA produced by PLD1 activity during compatible pollination promotes vesicle fusion at the membrane to facilitate exocytosis necessary for pollen germination to occur, while SI response could abrogate this process by targeting PLD1 for degradation.

Effects of climate change on the distribution of hoverfly species (Diptera: Syrphidae) in Southeast Europe

Climate change presents a serious threat to global biodiversity. Loss of pollinators in particular has major implications, with extirpation of these species potentially leading to severe losses in agriculture and, thus, economic losses. In this study, we forecast the effects of climate change on the distribution of hoverflies in Southeast Europe using species distribution modelling and climate change scenarios for two time-periods. For 2041–2060, 19 analysed species were predicted to increase their areas of occupancy, with the other 25 losing some of their ranges. For 2061–2080, 55% of species were predicted to increase their area of occupancy, while 45% were predicted to experience range decline. In general, range size changes for most species were below 20%, indicating a relatively high resilience of hoverflies to climate change when only environmental variables are considered. Additionally, range-restricted species are not predicted to lose more area proportionally to widespread species. Based on our results, two distributional trends can be established: the predicted gain of species in alpine regions, and future loss of species from lowland areas. Considering that the loss of pollinators from present lowland agricultural areas is predicted and that habitat degradation presents a threat to possible range expansion of hoverflies in the future, developing conservation management strategy for the preservation of these species is crucial. This study represents an important step towards the assessment of the effects of climate changes on hoverflies and can be a valuable asset in creating future conservation plan, thus helping in mitigating potential consequences.

Attractiveness of wildflower mixtures for wild bees and hoverflies depends on some key plant species

Abstract Agricultural intensification is considered to be a major driver of terrestrial biodiversity decline. Resulting loss, isolation and degradation of flower‐rich habitats are threatening pollinators. Agri‐environmental schemes (AES) aim to counteract these negative effects, including measures to enhance floral resources in agricultural landscapes. The impact of plant species composition on their efficiency to mitigate pollinator loss, however, is largely unexplored. We tested four recommended seed mixtures for their attractiveness to wild bees and hoverflies in a replicated plot design over two consecutive years against the background of the seedbank. Of the 94 available plant species, 14 key plant species were crucial for the whole flower‐visiting bee and hoverfly community. Approximately one third of each originated from the seedbank. The four top plants already supported 80% of flower visitors. Although seed mixtures differed significantly in attracting flower visitors at the plot level, the presence of key plants was more important than plant species diversity per se. Seed mixtures showed contrasting attractiveness for wild bees and hoverflies. Identification of plant species exclusively utilised by specific taxonomic groups opens opportunities for assorting plant mixtures for specific ecosystem functions or taxa of conservation concern. Plant species shared by common pollinators are valuable for overall pollinator diversity. The fact that rare and specialised pollinator species were mostly absent, however, substantiates that within 2 years of establishment, flowering resources are not the sole limiting factor in modern agricultural landscapes. Considering additional resources seems indispensable to maximise the conservation of species‐rich pollinator communities.

Projected climate change threatens pollinators and crop production in Brazil

Animal pollination can impact food security since many crops depend on pollinators to produce fruits and seeds. However, the effects of projected climate change on crop pollinators and therefore on crop production are still unclear, especially for wild pollinators and aggregate community responses. Using species distributional modeling, we assessed the effects of climate change on the geographic distribution of 95 pollinator species of 13 Brazilian crops, and we estimated their relative impacts on crop production. We described these effects at the municipality level, and we assessed the crops that were grown, the gross production volume of these crops, the total crop production value, and the number of inhabitants. Overall, considering all crop species, we found that the projected climate change will reduce the probability of pollinator occurrence by almost 0.13 by 2050. Our models predict that almost 90% of the municipalities analyzed will face species loss. Decreases in the pollinator occurrence probability varied from 0.08 (persimmon) to 0.25 (tomato) and will potentially affect 9% (mandarin) to 100% (sunflower) of the municipalities that produce each crop. Municipalities in central and southern Brazil will potentially face relatively large impacts on crop production due to pollinator loss. In contrast, some municipalities in northern Brazil, particularly in the northwestern Amazon, could potentially benefit from climate change because pollinators of some crops may increase. The decline in the probability of pollinator occurrence is found in a large number of municipalities with the lowest GDP and will also likely affect some places where crop production is high (20% to 90% of the GDP) and where the number of inhabitants is also high (more than 6 million people). Our study highlights key municipalities where crops are economically important and where pollinators will potentially face the worst conditions due to climate change. However, pollinators may be able to find new suitable areas that have the potential to improve crop production. The results shown here could guide policy decisions for adapting to climate change and for preventing the loss of pollinator species and crop production.