Identification of nectar sources foraged by female mosquitoes in Canada.

For many mosquito species, the females must obtain vertebrate blood to complete a gonotrophic cycle. These blood meals are frequently supplemented by feeding on sugary plant nectar, which sustains energy reserves needed for flight, mating, and overall fitness. Our understanding of mosquito nectar foraging behaviors is mostly limited to laboratory experiments and direct field observations, with little research into natural mosquito-host plant relationships done in North America. In this study, we collected nectar-fed female mosquitoes over a 2-year period in Manitoba, Canada, and amplified a fragment of the chloroplast rbcL gene to identify the plant species fed upon. We found that mosquitoes foraged from diverse plant families (e.g., grasses, trees, ornamentals, and legumes), but preferred certain species, most notably soybean and Kentucky blue grass. Moreover, there appeared to be some associations between plant feeding preferences and mosquito species, date of collection, landscape, and geographical region. Overall, this study implemented DNA barcoding to identify nectar sources forage by mosquitoes in the Canadian Prairies.

Harnessing artificial intelligence for analysing the impacts of nectar and pollen feeding in conservation biological control.

Plant-derived foods, such as nectar and pollen, have garnered substantial research attention due to their potential to support natural enemies of pests. This review is a pioneering exploration of the potential for artificial intelligence approaches to provide insights into the factors that drive the success of conservation biological control (CBC). Nectar and pollen were confirmed as key plant food resources for natural enemies. These have been widely used across differing crop systems and provided by a wide range of CBC interventions, such as field margin flower strips. The combined use of parasitoids and predators is revealed as more successful than either of these guilds alone. CBC success was greater in field crops than in vine and berry crops, whilst interventions using dicotyledonous species that produce nectar in addition to pollen were more successful than using grassy interventions.

Effect of the partial substitution of mango and ground chia on the antioxidant capacity in the elaboration of nectar based on sachatomate.

The consumption of products with high nutritional value and antioxidant capacity has increased notably in recent years. Due to health problems such as triglycerides and cardiovascular problems, its use is becoming reduced. So that, chia (Salvia hispánica) and sachatomate (Cyphomandra betacea) have gained interest as an alternative to develop nutraceutical products, compared to conventional products. The objective of the study was to determine the effect of the partial substitution of mango (Mangifera indica) and ground chia (Salvia hispánica) on the antioxidant capacity in the elaboration of nectar based on Sachatomate. The physicochemical characteristics were determined where sample 11 complies with the established parameters: 13.4° Brix, pH 4.323, 0.354 of C6-H8-O7 and viscosity 3967.3 mPas, according to the NTP 203.110 standard. Regarding the antioxidant capacity, sample 12 was the most optimal, according to the DPPH method, it has been determined 104.3 micromoles Trolox equivalents; according to the ABTS method, it was determined with an antioxidant content of 187.4 micromoles Trolox equivalents. Regarding the proximal chemical evaluation, sample 12 was determined to be the most suitable with a moisture percentage of 87.45%, ash 0.32%, crude fiber 0.09%, fat 0.10%, protein 0.45% and carbohydrates 11.59%. Concluding that substituting sachatomate and ground chia significantly influences the antioxidant capacity, increasing to 104.3 and 187.4 micromoles Trolox equivalents, determined by both methods, indicates that nectar consumption can be used to improve the health of consumers.

Protein/Lipid ratio of pollen biases the visitation of bumblebees (Bombus ignitus Smith) to male-fertile cultivars of the Japanese pear (Pyrus pyrifolia Nakai).

Bees have been known to visit the male-fertile cultivars of self-incompatible flowering plants more frequently than the male-sterile cultivars, but the origin of this preference is poorly understood. Here, we demonstrate that this preference is driven by the higher protein/lipid ratio of male-fertile pollen compared with male-sterile pollen by way of two caged-behavioral assays with six cultivars. In the first assay, flower-naïve bumblebees (Bombus ignitus Smith) showed a significantly higher flower-visitation rate to male-fertile cultivars (pollen germination rate > 55%; > 14 visits/10 min) of the Japanese pear (Pyrus pyrifolia Nakai) than male-sterile cultivars (pollen germination rate ≤ 20%; > 6 visits/10 min). In the second, bees still preferred the anthers of male-fertile cultivars (5-9 visits/10 min) more than those of male-sterile ones (less than 1 visit in 10 min) even in the absence of all other organs (i.e., petals, pistil, nectar), indicating that pollen is responsible for the preference. We then analyzed the macronutrient content of the pollen and its visual cues, and found that the bee preference was highly correlated with the protein/lipid ratio (0.3-1.6) but not color variables such as (a)chromatic contrast, intensity, and spectral purity. We conclude that the protein/lipid ratio influences the foraging behavior of the bumblebees likely by serving as (1) a chemotactile cue while antennating, (2) a gustatory cue after intake, and (3) an olfactory cue. In addition, the low bee visitation rate to poorly viable pollen could be due to its low protein/lipid ratio.

Biochemical characterization of Euphorbia resinifera floral cyathia.

Euphorbia resinifera O. Berg is a plant endemic to the Northern and Central regions of Morocco known since the ancient Roman and Greek times for secreting a poisonous latex containing resiniferatoxin. However, E. resinifera pseudo-inflorescences called cyathia are devoid of laticifers and, therefore, do not secrete latex. Instead, they exudate nectar that local honey bees collect and craft into honey. Honey and cyathium water extracts find a broad range of applications in the traditional medicine of Northern Africa as ointments and water decoctions. Moreover, E. resinifera monofloral honey has received the Protected Geographic Indication certification for its outstanding qualities. Given the relevance of E. resinifera cyathia for bee nutrition, honey production, and the health benefit of cyathium-derived products, this study aimed to screen metabolites synthesized and accumulated in its pseudo-inflorescences. Our analyses revealed that E. resinifera cyathia accumulate primary metabolites in considerable abundance, including hexoses, amino acids and vitamins that honey bees may collect from nectar and craft into honey. Cyathia also synthesize volatile organic compounds of the class of benzenoids and terpenes, which are emitted by flowers pollinated by honey bees and bumblebees. Many specialized metabolites, including carotenoids, flavonoids, and polyamines, were also detected, which, while protecting the reproductive organs against abiotic stresses, also confer antioxidant properties to water decoctions. In conclusion, our analyses revealed that E. resinifera cyathia are a great source of antioxidant molecules and a good food source for the local foraging honeybees, revealing the central role of the flowers from this species in mediating interactions with local pollinators and the conferral of medicinal properties to plant extracts.

Identification of floral volatiles from Fagopyrum esculentum that attract Cotesia vestalis with potentially better biocontrol efficacy against Plutella xylostella.

BACKGROUND: Nectar plants provide extra nourishment for parasitoids, which can utilize floral volatiles to locate nectar-rich flowers. A promising strategy is to screen potential floral species based on the wasps' olfactory preferences for nectar sources, and to ensure their suitability for both natural enemies and targeted pests. Cotesia vestalis (Haliday) is a dominant parasitoid of the oligophagous pest Plutella xylostella, which poses a significant threat to cruciferous vegetables globally. However, the chemical cues in plant-parasitoid complexes mediating Cotesia vestalis to locate nectar food resources and the positive effect of nectar plants on the Cotesia vestalis population are poorly understood. RESULTS: The results showed that Fagopyrum esculentum was the most attractive plant that attracted Cotesia vestalis, not Plutella xylostella in 44 flowering plants from 19 families. 1,2-Diethyl benzene and 1,4-diethyl benzene, identified from the floral volatiles from F. esculentum in full bloom, were found to elicit dose-dependent electrophysiological responses and attract Cotesia vestalis adults, demonstrating their potential as semiochemicals. Moreover, the age-stage, two-sex life table revealed that feeding on nectar food increased the efficacy of Cotesia vestalis adults against Plutella xylostella. CONCLUSION: In summary, the findings provide insights into the chemical ecology of plant-parasitoid complexes and support the potential use of F. esculentum as insectary plants in habitat manipulation against Plutella xylostella by supplying natural nectar food for the Cotesia vestalis population. Our results suggest an attract and reward strategy based on an attractant for Cotesia vestalis to control Plutella xylostella, or the development of volatile-based artificial food for Cotesia vestalis. © 2023 Society of Chemical Industry.

Residue dynamics of a contact and a systemic fungicide in pollen, nectar, and other plant matrices of courgette (Cucurbita pepo L.).

Pollen and nectar can be contaminated with a range of pesticides, including insecticides, fungicides, and herbicides. Since these matrices are important food sources for pollinators and other beneficial insects, their contamination can represent a key route of exposure. However, limited knowledge exists with respect to pesticide residue levels and their dynamics in these matrices for many crops and active ingredients (AIs). We used controlled glasshouse studies to investigate the residue dynamics of a systemic (cyprodinil) and a contact (fludioxonil) fungicide in the floral matrices and other plant parts of courgette/zucchini (Cucurbita pepo L.). We aimed to better understand the processes behind residue accumulation and decline in pollen and nectar. Each AI was applied to plants, either by spraying whole plants or by targeted spraying onto leaves only. Samples of pollen, nectar, anthers, flowers, and leaves were taken on the day of application and each subsequent morning for up to 13 days and analysed for residues using LC-MS/MS. Significant differences in residue levels and dynamics were found between AIs and floral matrices. The present study allowed for the identification of potential routes by which residues translocate between tissues and to link those to the physicochemical properties of each AI, which may facilitate the prediction of residue levels in pollen and nectar. Residues of the contact AI declined more quickly than those of the systemic AI in pollen and nectar. Our results further suggest that the risk of oral exposure for pollinators may be considerably reduced by using contact AIs during the green bud stage of plants, but application of systemic compounds could still result in a low, but continuous long-term exposure for pollinators with limited decline.

Elevated rates of dietary generalization in eusocial lineages of the secondarily herbivorous bees.

BACKGROUND: Within the Hymenoptera, bees are notable for their relationship with flowering plants, being almost entirely dependent on plant pollen and nectar. Though functionally herbivorous, as a result of their role as pollinators, bees have received comparatively little attention as models for insect herbivory. Bees often display dietary specialization, but quantitative comparison against other herbivorous insects has not previously been conducted. RESULTS: In the most comprehensive analysis to date for 860 bee species, dietary specialization amounted to 50.1% of studied species collecting pollen from between 1 and 2 botanical families with a relatively long tail of dietary generalists, with 11.1% of species collecting from more than 10 botanical families. This distribution deviated from the truncated Pareto distribution of dietary breadth seen in other herbivorous insect lineages. However, this deviation was predominantly due to eusocial bee lineages, which show a range of dietary breadths that conformed to a normal distribution, while solitary bees show a typical truncated distribution not strongly different from other herbivorous insects. We hypothesize that the relatively low level of dietary specialization in bees as a whole reflects the relaxation of the constraints typically observed in herbivorous insects with a comparatively reduced importance of plant chemistry and comparatively increased importance of phenology and foraging efficiency. The long flight periods of eusocial bees that are necessary to allow overlapping generations both allows and necessitates the use of multiple flowering resources, whereas solitary bees with short flight periods have more limited access to varied resources within a constrained activity period. CONCLUSIONS: Collectively, solitary bees show slightly lower specialization compared to other herbivorous insects, possibly due to their balanced relationship with plants, rather than direct antagonism such as seen in the direct consumption of plant tissues. An additional factor may be the mediocre diversity of bees at low latitudes combined with low levels of dietary specialization, whereas these areas typically display a high rate of specialization by herbivorous insects in general. Though the most important factors structuring dietary specialization in bees appear to differ from many other herbivorous insects, solitary bees show a surprisingly similar overall pattern of dietary specialization.

Global assessment of honeybee exposure to pesticides through guttation consumption: An indicator approach.

Guttation consumption is a potential pathway of pesticide residue exposure in honeybees. However, modeling tools for assessing honeybee exposure to pesticide residues in guttation drops are lacking. In this study, we propose an indicator-based approach for qualitatively or quantitatively analyzing the guttation-based exposure pathway, allowing us to conduct region-specific pesticide residue exposure assessments for honeybees. Exposure scores (the product of guttation production and residue level scores) were established to compare or rank honeybee exposure to pesticide residues via guttation intake across locations using three specified indicators (i.e., air temperature, relative humidity, and precipitation intensity). Warm, dry regions had high residue level scores (indicating high residue levels in guttation), whereas cold, wet regions had high guttation production scores (indicating high possibilities of guttation formation on leaf surfaces); their exposure scores were a combination of these two values. We evaluated and ranked honeybee exposure to imidacloprid residue across regions in Brazil, China, the United States, and selected European Union member states, revealing that pesticide application in many Brazilian federative units may raise honeybee risks due to high exposure scores. We also compared the guttation pathway to other common exposure pathways (nectar and pollen), suggesting that for some moderately lipophilic compounds, the guttation exposure pathway may not be ignored and should be further evaluated.

Spatio-temporal expression of candidate genes for nectar spur development in Tropaeolum (Tropaeolaceae: Brassicales).

BACKGROUND AND AIMS: Tropaeolaceae (Brassicales) comprise ~100 species native to South and Central America. Tropaeolaceae flowers have a nectar spur, formed by a late expansion and evagination of the fused proximal region of the perianth (i.e. the floral tube). This spur is formed in the domain of the tube oriented towards the inflorescence axis, which corresponds to the adaxial floral region. However, little is known about the molecular mechanisms responsible for the evolution of spurs in Tropaeolaceae. METHODS: In this study, we examined the spatio-temporal expression of genes putatively responsible for differential patterns of cell division between the adaxial and abaxial floral regions in Tropaeolaceae. These genes include previously identified TCP and KNOX transcription factors and the cell division marker HISTONE H4 (HIS4). KEY RESULTS: We found a TCP4 homologue concomitantly expressed with spur initiation and elaboration. Tropaeolaceae possess two TCP4-like (TCP4L) copies, as a result of a Tropaeolaceae-specific duplication. The two copies (TCP4L1 and TCP4L2) in Tropaeolum longifolium show overlapping expression in the epidermis of reproductive apices (inflorescence meristems) and young floral buds, but only TlTCP4L2 shows differential expression in the floral tube at early stages of spur formation, restricted to the adaxial region. This adaxial expression of TlTCP4L2 overlaps with the expression of TlHIS4. Later in development, only TlTCP4L2 is expressed in the nectariferous tissue of the spur. CONCLUSIONS: Based on these results, we hypothesize that Tropaeolaceae TCP4L genes had a plesiomorphic role in epidermal development and that, after gene duplication, TCP4L2 acquired a new function in spur initiation and elaboration. To better understand spur evolution in Tropaeolaceae, it is critical to expand developmental genetic studies to their sister group, the Akaniaceae, which possess simultaneously an independent duplication of TCP4L genes and a spurless floral tube.

The yield of common buckwheat (Fagopyrum esculentum Moench) depends on the genotype but not on the Pin-to-Thrum ratio.

Common buckwheat has a complicated flowering biology. It is characterized by a strong self-incompatibility resulting from heterostyly, i.e. the occurrence of two types of flowers: Pin and Thrum, differing in the length of pistils and stamens. Fertilization occurs only as a result of cross-pollination between these morphs. Suspicions exist that the disturbed ratio between plants producing Pin and Thrum flowers (with the latter type generating more seeds) causes low seed yield. The aim of the study was to analyze: (1) the ratio between plants with Pin and Thrum morphs, (2) flower and seed production, as well as abortion of flowers, (3) the composition of nectar collected at an early flowering stage and during full flowering. The study was performed under semi-controlled and field conditions on six Polish accessions. The results indicated that under semi-controlled conditions the Pin-to-Thrum ratio was indeed disproportionate; such a phenomenon is called anisoplethy. In the field, however, the Pin-to-Thrum ratio was well-balanced (isoplethy). The plants with both morphs aborted a similar percentage of flowers and produced a comparable number of empty seeds. The number of flowers, their abortion, and ripe seed production were independent of flower type, however, they were genotypically controlled. A strong correlation between the number of flowers produced by a plant, flower abortion and the number of empty seeds was found. The percentage of aborted flowers correlated positively with the weight of ripe seeds. Nectar composition was similar for all buckwheat genotypes, but we found some differences in the amount of individual sugars depending on the blooming stage. In the majority of accessions, the nectar produced at the early blooming stage was characterized by a greater mass and volume, and contained more individual sugars than at the full-flowering stage.

Honeybees' foraging choices for nectar and pollen revealed by DNA metabarcoding.

Honeybees are the most widespread managed pollinators of our food crops, and a crucial part of their well-being is a suitable diet. Yet, we do not know how they choose flowers to collect nectar or pollen from. Here we studied forty-three honeybee colonies in six apiaries over a summer, identifying the floral origins of honey and hive-stored pollen samples by DNA-metabarcoding. We recorded the available flowering plants and analyzed the specialized metabolites in honey. Overall, we find that honeybees use mostly the same plants for both nectar and pollen, yet per colony less than half of the plant genera are used for both nectar and pollen at a time. Across samples, on average fewer plant genera were used for pollen, but the composition was more variable among samples, suggesting higher selectivity for pollen sources. Of the available flowering plants, honeybees used only a fraction for either nectar or pollen foraging. The time of summer guided the plant choices the most, and the location impacted both the plants selected and the specialized metabolite composition in honey. Thus, honeybees are selective for both nectar and pollen, implicating a need of a wide variety of floral resources to choose an optimal diet from.

Night and day: Contributions of diurnal and nocturnal visitors to pollen dispersal, paternity diversity, and fruit set in an early-blooming shrub, Daphne jezoensis.

PREMISE: Under uncertain pollinator visit conditions, plants often exhibit long flowering periods and generalized pollination systems. Flowering of the gynodioecious shrub Daphne jezoensis occurs in early spring in cool temperate forests. Pollination by nocturnal moths is expected, given the species' tubular-shaped flowers with sweet fragrance and nectar. However, the effectiveness of nocturnal moths under cool conditions is unknown. We evaluated the relative importance of diurnal and nocturnal visitors as pollinators in early spring. METHODS: We investigated flowering duration, flower visitors, and floral scents in a natural population. We experimentally exposed flowers to visitors only during daytime or nighttime using bagging treatments and evaluated the contributions of diurnal and nocturnal insects to fruit set, pollen dispersal distance, and paternity diversity using 16 microsatellite markers. RESULTS: Female flowers lasted ~3 wk, which was ~8 d longer than the flowering period of hermaphrodites. Various insects, including Coleoptera, Diptera, Hymenoptera, and Lepidoptera, visited the flowers during both daytime and nighttime. Flowers emitted volatiles, such as lilac aldehyde isomers and ß-ocimene, which are known to attract moths. Fruit-set rate in the night-open treatment was similar to or higher than that in the day-open treatment. However, pollen dispersal distance in the night-open treatment was shorter than that in the day-open treatment. Paternity diversity was similar in day-open and night-open treatments. CONCLUSIONS: Early-blooming plants ensure pollen receipt and dispersal by having a long flowering period and using both diurnal and nocturnal flower visitors, suggesting the importance of a generalized pollination system under uncertain pollinator visit conditions.

The Effect of Stimulants on Nectar Composition, Flowering, and Seed Yield of Common Buckwheat (Fagopyrum esculentum Moench).

Common buckwheat is a valuable plant producing seeds containing a number of health-promoting compounds and elements. Buckwheat does not contain gluten and is characterized by an excellent composition of amino acids. This species is also a melliferous plant. Despite many advantages, the area of buckwheat cultivation is decreasing due to unstable yields. One of the reasons for low seed yield is its sensitivity to drought, high temperatures, and assimilate deficiencies. These factors have a significant impact on the nectar composition, which is important for visiting pollinators and thus for pollination. High temperature during flowering increases the degeneration of embryo sacs and embryos, which is high anyway (genetic determination) in common buckwheat. This phenomenon seems to be unbreakable by breeding methods. The authors aimed to determine whether stimulants commonly used in agriculture could increase the seed yield of this plant species. The aim of the work was to choose from eight different stimulants the most effective one that would improve the seed yield of two accessions of common buckwheat by increasing the efficiency of nectar production and reducing the number of empty seeds. The plants were sprayed at either the beginning of flowering or at full bloom. The content of sugars and amino acids was higher in the nectar produced at the beginning of flowering. The nectar of both lines included also polyamines. The level of sugars in the nectar increased mainly after spraying with the stimulants in the second phase of flowering. A positive correlation between the total amount of sugars and amino acids in the nectar and seed yield was found. All the stimulants used reduced the number of empty seeds in both accessions. Seed production in the PA15 line increased significantly under the influence of all stimulants used at the beginning of flowering, and the most effective were ASAHI SL and TYTANIT®.

Sterol composition in plants is specific to pollen, leaf, pollination and pollinator.

Sterols have several roles in planta, including as membrane components. Sterols are also essential nutrients for insects. Based on this, and the different functions of leaves and pollen, we tested the hypotheses that (a) the sterolome is different in leaves and pollen from the same plant, (b) pollens from wind- and insect pollinated plants comprise different sterols, and (c) sterol provision in pollen-rewarding angiosperms differs from nectar-rewarding species. A novel approach to sterolomics was developed, using LCMS to determine the sterol profile of leaf and pollen from a taxonomically diverse range of 36 plant species. Twenty-one sterols were identified unambiguously, with several more identified in trace amounts. C29 sterols dominated the sterolome in most plants. The sterol composition was significantly different in leaf and pollen and their main sterols evolved in different ways. The sterolome of pollen from animal- and wind-pollinated was also significantly different, but not between nectar- and pollen-rewarding species. Our results suggest that the sterol composition in different plant tissues is linked to their biological functions. Sterol composition in pollen might be driven by physical role rather than the nutrient needs of pollinating insects.

Fungicides and strawberry pollination-Effects on floral scent, pollen attributes and bumblebee behavior.

Fungicides are used in agriculture to protect crops from various fungal diseases. However, they may modulate the plants metabolism. Moreover, fungicides can accumulate in the environment and may cause toxic effects on non-target organisms such as nectar microbes and pollinators. Nectar microbes contribute to the volatile profile of flowers and can influence pollinators behaviour. Thus, fungicide treatment could potentially affect the pollination. In this study, we investigated the influence of fungicide treatment on floral attributes as well as the behavioural impact on bumblebees. In separate experiments, we used one or both strawberry cultivars (Fragaria × ananassa var. Darselect and Malwina), which were either kept untreated (control) or treated with either Cuprozin® progress or SWITCH® fungicide. We analysed various flower traits including volatiles, pollen weight, pollen protein, and the attraction of bumblebees towards the flowers in the greenhouse. Additionally, we analysed the viability of pollen and pollen live-to-dead ratio, as well as the composition of nectar fungi in the field. A treatment with Cuprozin® progress led to a lower emission of floral volatiles and a slightly lower pollen protein content. This had no impact on the visit latency of bumblebees but on the overall visit frequency of these flowers. The treatment with the fungicide SWITCH® resulted in a higher emission of floral volatiles as well as a delayed first visit by bumblebees. Furthermore, flowers of control plants were visited more often than those treated with the two fungicides. Plant-pollinator interactions are highly complex, with many contributing factors. Fungicides can have an impact on the pollen quality and pollinator attraction, potentially leading to an altered pollen dispersal by pollinators and a change in fruit quality.

Female solitary bees flexibly change foraging behaviour according to their floral resource requirements and foraging experiences.

Intraspecific variation in foraging behaviour is related to the floral resource requirements and foraging experiences of social bees. These behavioural changes influence their pollination efficiency. However, the extent of such behavioural changes in solitary bees, which constitute the majority of bee species, remains largely unknown. As pollen contains essential nutrients for ovarian and offspring development, a relationship between the resource requirements of female bees and their ovarian development is expected. Additionally, wing damage could reflect foraging experiences, as the wings are damaged during foraging. Here, we aimed to clarify the relationships between ovarian development, wing damage, foraging behaviours, and pollination efficiency in female long-horned bees (Eucera nipponensis and Eucera spurcatipes) visiting red clovers. The bee handling times were recorded. Wing damage and pollen load on the hind legs were confirmed and the number of pollen grains on bee's bodies was counted. We then dissected the bees and recorded the presence or absence of nectar and pollen in the digestive tubes, as well as the mature egg number. The mature egg number positively correlated with nectar feeding and pollen collection, whereas handling time decreased with wing damage. Bees with pollen loads on their legs attach more pollen grains to their bodies. Therefore, solitary bees flexibly change their foraging behaviour based on resource requirements and foraging experiences, and these behavioural changes can influence pollination efficiency. The asynchrony of foraging behaviours and pollination efficiency within a bee population may provide stable pollination for flowering plants throughout the season.

A critical review on the accumulation of neonicotinoid insecticides in pollen and nectar: Influencing factors and implications for pollinator exposure.

Neonicotinoids are a class of neuro-active insecticides widely used to protect major crops, primarily because of their broad-spectrum insecticidal activity and low vertebrate toxicity. Owing to their systemic nature, plants readily take up neonicotinoids and translocate them through roots, leaves, and other tissues to flowers (pollen and nectar) that serve as a critical point of exposure to pollinators foraging on treated plants. The growing evidence for potential adverse effects on non-target species, especially pollinators, and persistence has raised serious concerns, as these pesticides are increasingly prevalent in terrestrial and aquatic systems. Despite increasing research efforts, our understanding of the potential toxicity of neonicotinoids and the risks they pose to non-target species remains limited. Therefore, this critical review provides a succinct evaluation of the uptake, translocation, and accumulation processes of neonicotinoids in plants and the factors that may affect the eventual build-up of neonicotinoids in pollen and nectar. The role of plant species, as well as the physicochemical properties and application methods of neonicotinoids is discussed. Potential knowledge gaps are identified, and questions meriting future research are suggested for improving our understanding of the relationship between neonicotinoid residues in plants and exposure to pollinators.

Fertilizer and herbicide alter nectar and pollen quality with consequences for pollinator floral choices.

Background: Pollinating insects provide economically and ecologically valuable services, but are threatened by a variety of anthropogenic changes. The availability and quality of floral resources may be affected by anthropogenic land use. For example, flower-visiting insects in agroecosystems rely on weeds on field edges for foraging resources, but these weeds are often exposed to agrochemicals that may compromise the quality of their floral resources. Methods: We conducted complementary field and greenhouse experiments to evaluate the: (1) effect of low concentrations of agrochemical exposure on nectar and pollen quality and (2) relationship between floral resource quality and insect visitation. We applied the same agrochemcial treatments (low concentrations of fertilizer, low concentrations of herbicide, a combination of both, and a control of just water) to seven plant species in the field and greenhouse. We collected data on floral visitation by insects in the field experiment for two field seasons and collected pollen and nectar from focal plants in the greenhouse to avoid interfering with insect visitation in the field. Results: We found pollen amino acid concentrations were lower in plants exposed to low concentrations of herbicide, and pollen fatty acid concentrations were lower in plants exposed to low concentrations of fertilizer, while nectar amino acids were higher in plants exposed to low concentrations of either fertilizer or herbicide. Exposure to low fertilizer concentrations also increased the quantity of pollen and nectar produced per flower. The responses of plants exposed to the experimental treatments in the greenhouse helped explain insect visitation in the field study. The insect visitation rate correlated with nectar amino acids, pollen amino acids, and pollen fatty acids. An interaction between pollen protein and floral display suggested pollen amino acid concentrations drove insect preference among plant species when floral display sizes were large. We show that floral resource quality is sensitive to agrochemical exposure and that flower-visiting insects are sensitive to variation in floral resource quality.

Pollination by sexual deception.

The flower is arguably the centrepiece of angiosperm evolution. Its primary function is to secure pollination - the transfer of pollen from the anther (male) to the stigma (female). As plants are sessile organisms, the extraordinary diversity of flowers in large part reflects countless alternative evolutionary solutions to achieve this critical step in the flowering plant life cycle. The majority of flowering plants, some 87% by one estimate, depend on animals for pollination, with most of these paying for the service of pollination via food rewards of nectar or pollen. As in human economic systems, however, some cheating and deception occurs, with the pollination strategy of sexual deception being one such example.