Sugar-conditioned honey bees can be biased towards a nectarless dioecious crop.

The targeted pollination strategy has shown positive results in directing honey bees to crop flowers offering nectar along with pollen as reward. Kiwifruit is a functionally dioecious species, which relies on bees to transport pollen from staminate to pistillate nectarless flowers. Following the targeted pollination procedures recently validated, we first developed a mimic odor (KM) based on kiwifruit floral volatiles for which bees showed the highest level of generalization to the natural floral scent, although the response towards pistillate flowers was higher than towards staminate flowers. Then, in the field, feeding colonies KM-scented sucrose solution resulted in higher amounts of kiwifruit pollen collected by honey bees compared to control colonies fed unscented sucrose solution. Our results support the hypothesis that olfactory conditioning bees biases their foraging preferences in a nectarless crop, given the higher visitation to target flowers despite having provided the mimic odor paired with a sugar reward.

Genotypic variation in blueberry flower morphology and nectar reward content affects pollinator attraction in a diverse breeding population.

BACKGROUND: Pollination is crucial to obtaining optimal blueberry yield and fruit quality. Despite substantial investments in seasonal beekeeping services, blueberry producers consistently report suboptimal pollinator visitation and fruit set in some cultivars. Flower morphology and floral rewards are among the key factors that have shown to contribute to pollinator attraction, however little is known about their relative importance for improving yield in the context of plant breeding. Clarifying the relationships between flower morphology, nectar reward content, pollinator recruitment, and pollination outcomes, as well as their genetic components, can inform breeding priorities for enhancing blueberry production. In the present study, we measured ten flower and nectar traits and indices of successful pollination, including fruit set, seed count, and fruit weight in 38 southern highbush blueberry genotypes. Additionally, we assessed pollinator visitation frequency and foraging behavior over two growing seasons. Several statistical models were tested to optimize the prediction of pollinator visitation and pollination success, including partial least squares, BayesB, ridge-regression, and random forest. RESULTS: Random forest models obtained high predictive abilities for pollinator visitation frequency, with values of 0.54, 0.52, and 0.66 for honey bee, bumble bee, and total pollinator visits, respectively. The BayesB model provided the most consistent prediction of fruit set, fruit weight, and seed set, with predictive abilities of 0.07, -0.08, and 0.42, respectively. Variable importance analysis revealed that genotypic differences in nectar volume had the greatest impact on honey bee and bumble bee visitation, although preferences for flower morphological traits varied depending on the foraging task. Flower density was a major driving factor attracting nectar-foraging honey bees and bumble bees, while pollen-foraging bumble bees were most influenced by flower accessibility, specifically corolla length and the length-to-width ratio. CONCLUSIONS: Honey bees comprised the majority of pollinator visits, and were primarily influenced by nectar volume and flower density. Corolla length and the length-to-width ratio were also identified as the main predictors of fruit set, fruit weight, seed count, as well as pollen-foraging bumble bee visits, suggesting that these bees and their foraging preferences may play a pivotal role in fruit production. Moderate to high narrow-sense heritability values (ranging from 0.30 to 0.77) were obtained for all floral traits, indicating that selective breeding efforts may enhance cultivar attractiveness to pollinators.

Effects of flowering period on floral traits, pollinator behavior and seed production of David's mountain laurel (Sophora davidii).

Sophora davidii is a cross-pollinated plant with important ecological protection and medicinal value in China, but its seed yield is low due to backward and nonstandard production technology. Therefore, we divide the flowering period of Sophora davidii into initial, full and final flowering period, measuring the floral morphology, pollen viability, stigma receptivity, nectar volume and nectar concentration, foraging behavior of pollinators, fertilization physiology, seed yield and quality through field observation and indoor testing to explore whether the flowering period affects the floral traits, pollinator behavior and seed production of plants. Our results revealed that the nectar volume, nectar concentration, pollen viability and stigma receptivity at full flowering period were the highest. The single visit time and visit time per flower of Chinese honey bees were the longest in the full flowering period, while the number of transfer, visit frequency and number of touching stigma were the least. The visiting number of the bees was the most and the most active in the full flowering period. The bees pollination not only improved the pollen amount, germination rate, pollen tube length and the ovule number of S. davidii, but also their effect was the most obvious in full flowering period. The principal component analysis showed that pollination by Chinese honey bees during the whole flowering period of S. davidii was the best way to produce seeds. We can conclude that flowering period affects flower traits, foraging behavior of pollinators, seed yield and quality of S. davidii.

Honey bee colonies can buffer short-term stressor effects of pollen restriction and fungicide exposure on colony development and the microbiome.

Honey bees (Apis mellifera) have to withstand various environmental stressors alone or in combination in agriculture settings. Plant protection products are applied to achieve high crop yield, but residues of their active substances are frequently detected in bee matrices and could affect honey bee colonies. In addition, intensified agriculture could lead to resource limitation for honey bees. This study aimed to compare the response of full-sized and nucleus colonies to the combined stressors of fungicide exposure and resource limitation. A large-scale field study was conducted simultaneously at five different locations across Germany, starting in spring 2022 and continuing through spring 2023. The fungicide formulation Pictor® Active (active ingredients boscalid and pyraclostrobin) was applied according to label instructions at the maximum recommended rate on oil seed rape crops. Resource limitation was ensured by pollen restriction using a pollen trap and stressor responses were evaluated by assessing colony development, brood development, and core gut microbiome alterations. Furthermore, effects on the plant nectar microbiome were assessed since nectar inhabiting yeast are beneficial for pollination. We showed, that honey bee colonies were able to compensate for the combined stressor effects within six weeks. Nucleus colonies exposed to the combined stressors showed a short-term response with a less favorable brood to bee ratio and reduced colony development in May. No further impacts were observed in either the nucleus colonies or the full-sized colonies from July until the following spring. In addition, no fungicide-dependent differences were found in core gut and nectar microbiomes, and these differences were not distinguishable from local or environmental effects. Therefore, the provision of sufficient resources is important to increase the resilience of honey bees to a combination of stressors.

How many animal-pollinated angiosperms are nectar-producing?

The diversity of plant-pollinator interactions is grounded in floral resources, with nectar considered one of the main floral rewards plants produce for pollinators. However, a global evaluation of the number of animal-pollinated nectar-producing angiosperms and their distribution world-wide remains elusive. We compiled a thorough database encompassing 7621 plant species from 322 families to estimate the number and proportion of nectar-producing angiosperms reliant on animal pollination. Through extensive sampling of plant communities, we also explored the interplay between nectar production, floral resource diversity, latitudinal and elevational gradients, contemporary climate, and environmental characteristics. Roughly 223 308 animal-pollinated angiosperms are nectar-producing, accounting for 74.4% of biotic-pollinated species. Global distribution patterns of nectar-producing plants reveal a distinct trend along latitudinal and altitudinal gradients, with increased proportions of plants producing nectar in high latitudes and altitudes. Conversely, tropical communities in warm and moist climates exhibit greater floral resource diversity and a lower proportion of nectar-producing plants. These findings suggest that ecological trends driven by climate have fostered the diversification of floral resources in warmer and less seasonal climates, reducing the proportion of solely nectar-producing plants. Our study provides a baseline for understanding plant-pollinator relationships, plant diversification, and the distribution of plant traits.

Frequency and behavior of Melipona stingless bees and orchid bees (Hymenoptera: Apidae) in relation to floral characteristics of vanilla in the Yucatán region of Mexico.

Vanilla planifolia is native to the Mexican tropics. Despite its worldwide economic importance as a source of vanilla for flavoring and other uses, almost all vanilla is produced by expensive hand-pollination, and minimal documentation exists for its natural pollination and floral visitors. There is a claim that vanilla is pollinated by Melipona stingless bees, but vanilla is more likely pollinated by orchid bees. Natural pollination has not been tested in the Yucatán region of Mexico, where both vanilla and potential native bee pollinators are endemic. We document for the first time the flowering process, nectar production and natural pollination of V. planiflora, using bagged flower experiments in a commercial planting. We also assessed the frequency and visitation rates of stingless bees and orchid bees on flowers. Our results showed low natural pollination rates of V. planifolia (~ 5%). Only small stingless bees (Trigona fulviventris and Nannotrigona perilampoides) were seen on flowers, but no legitimate visits were witnessed. We verified that there were abundant Euglossa and fewer Eulaema male orchid bees around the vanilla plants, but neither visited the flowers. The introduction of a colony of the stingless bee Melipona beecheii and the application of chemical lures to attract orchid bees failed to induce floral visitations. Melipona beecheii, and male orchid bees of Euglossa viridissima and E. dilemma may not be natural pollinators of vanilla, due to lack of attraction to flowers. It seems that the lack of nectar in V. planifolia flowers reduces the spectrum of potential pollinators. In addition, there may be a mismatch between the attractiveness of vanilla floral fragrances to the species of orchid bees registered in the studied area. Chemical studies with controlled experiments in different regions would be important to further elucidate the potential pollinators of vanilla in southern Mexico.

Body-size-dependent effects of landscape-level resource energetics on pollinator abundance in woodland remnants.

Land use change alters floral resource availability, thereby contributing to declines in important pollinators. However, the severity of land use impact varies by species, influenced by factors such as dispersal ability and resource specialization, both of which can correlate with body size. Here. we test whether floral resource availability in the surrounding landscape (the 'matrix') influences bee species' abundance in isolated remnant woodlands, and whether this effect varies with body size. We sampled quantitative flower-visitation networks within woodland remnants and quantified floral energy resources (nectar and pollen calories) available to each bee species both within the woodland and the matrix. Bee abundance in woodland increased with floral energy resources in the surrounding matrix, with strongest effects on larger-bodied species. Our findings suggest important but size-dependent effects of declining matrix floral resources on the persistence of bees in remnant woodlands, highlighting the need to incorporate landscape-level floral resources in conservation planning for pollinators in threatened natural habitats.

Foraging task specialization in honey bees (Apis mellifera): the contribution of floral rewards to the learning performance of pollen and nectar foragers.

Social insects live in communities where cooperative actions heavily rely on the individual cognitive abilities of their members. In the honey bee (Apis mellifera), the specialization in nectar or pollen collection is associated with variations in gustatory sensitivity, affecting both associative and non-associative learning. Gustatory sensitivity fluctuates as a function of changes in motivation for the specific floral resource throughout the foraging cycle, yet differences in learning between nectar and pollen foragers at the onset of food collection remain unexplored. Here, we examined nectar and pollen foragers captured upon arrival at food sources. We subjected them to an olfactory proboscis extension reflex (PER) conditioning using a 10% sucrose solution paired (S10%+P) or unpaired (S10%) with pollen as a co-reinforcement. For non-associative learning, we habituated foragers with S10%+P or S10%, followed by dishabituation tests with either a 50% sucrose solution paired (S50%+P) or unpaired (S50%) with pollen. Our results indicate that pollen foragers show lower performance than nectar foragers when conditioned with S10%. Interestingly, performance improves to levels similar to those of nectar foragers when pollen is included as a rewarding stimulus (S10%+P). In non-associative learning, pollen foragers tested with S10%+P displayed a lower degree of habituation than nectar foragers and a higher degree of dishabituation when pollen was used as the dishabituating stimulus (S10%+P). Altogether, our results support the idea that pollen and nectar honey bee foragers differ in their responsiveness to rewards, leading to inter-individual differences in learning that contribute to foraging specialization.

Eco-evolutionary processes shaping floral nectar sugar composition.

Floral nectar sugar composition is assumed to reflect the nutritional demands and foraging behaviour of pollinators, but the relative contributions of evolutionary and abiotic factors to nectar sugar composition remain largely unknown across the angiosperms. We compiled a comprehensive dataset on nectar sugar composition for 414 insect-pollinated plant species across central Europe, along with phylogeny, paleoclimate, flower morphology, and pollinator dietary demands, to disentangle their relative effects. We found that phylogeny was strongly related with nectar sucrose content, which increased with the phylogenetic age of plant families, but even more strongly with historic global surface temperature. Nectar sugar composition was also defined by floral morphology, though it was not related to our functional measure of pollinator dietary demands. However, specialist pollinators of current plant-pollinator networks predominantly visited plant species with sucrose-rich nectar. Our results suggest that both physiological mechanisms related to plant water balance and evolutionary effects related to paleoclimatic changes have shaped floral nectar sugar composition during the radiation and specialisation of plants and pollinators. As a consequence, the high velocity of current climate change may affect plant-pollinator interaction networks due to a conflicting combination of immediate physiological responses and phylogenetic conservatism.

Development and anatomy of petals with specialized nectar holder and pollen container in Fumarioideae (Papaveraceae).

MAIN CONCLUSION: Petal developmental characteristics in Fumarioideae were similar at early stages, and the specialized nectar holder/pollen container formed by the outer/inner petals. The micro-morphology of these two structures, however, shows diversity in seven species. Elaborate petals have been modified to form different types, including petal lobes, ridges, protuberances, and spurs, each with specialized functions. Nectar holder and pollen container presumably have a function in plant-pollinator interactions. In Fumarioideae, four elaborate petals of the disymmetric/zygomorphic flower present architecture forming the "nectar holder" and "pollen container" structure at the bottom and top separately. In the present study, the petals of seven species in Fumarioideae were investigated by scanning electron microscopy, light microscope, and transmission electron microscopes. The results show that petal development could divided into six stages: initiation, enlargement, adaxial/abaxial differentiation, elaborate specializations (sacs, spurs, and lobes formed), extension, and maturation, while the specialized "nectar holder" and "pollen container" structures mainly formed in stage 4. "Nectar holder" is developed from the shallow sac/spur differentiated at the base of the outer petal, eventually forming a multi-organized complex structure, together with staminal nectaries (1-2) with individual sizes. A semi-closed ellipsoidal "pollen container" is developed from the apical part of the 3-lobed inner petals fused by middle lobes and attain different sizes. The adaxial epidermis cells are specialized, with more distinct punctate/dense columnar protrusions or wavy cuticles presented on obviously thickening cell walls. In addition, a large and well-developed cavity appears between the inner and outer epidermis of the petals. As an exception, Hypecoum erectum middle lobes present stamen mimicry. Elaborate petal structure is crucial for comprehending the petal diversity in Fumarioideae and provides more evidence for further exploration of the reproductive study in Papaveraceae.

Characterization of near-field temporal and spatial variations of pesticide residues using honeybee specimens as bio-sensing matrices.

This study was prompted by recent reports of the ubiquity of neonicotinoids (neonics) in environment and the likelihood of exposures and health hazards to non-target organisms. We aimed to quantify neonics levels in time- and location-match pollen and nectar samples foraged by honeybees (Apis mellifera) and characterized the temporal and spatial variations using a relative potency factor method to determine the total neonic levels, expressed as the imidacloprid-adjusted total neonics, IMIRPF (ng/g). Six pairs of pollen and nectar samples, a total of twelve samples, were collected from each of the thirty-two experimental hives during the active foraging months of March, April, and June and analyzed for eight neonics. We found 59% and 64% of pollen and nectar contained at least one neonic, respectively. Among those neonic-detected pollen and nectar samples, 45% and 77% of them contained more than one neonic, respectively. Imidacloprid and acetamiprid in pollen and clothianidin and thiamethoxam in nectar accounted for 60% and 83% detection, respectively. The highest 3-month average of IMIRPF in pollen (6.56 ng/g) and nectar (11.19 ng/g) were detected in a location with the predominant production of citrus fruit. The temporal and spatial variations of IMIRPF levels demonstrated the robustness of using paired pollen and nectar data as the bio-sensing matrices to facilitate the assessment of near-field exposure to total neonics and the delineation of risks.

A multifunctional role for riboflavin in the yellow nectar of Capsicum baccatum and Capsicum pubescens.

A few Capsicum (pepper) species produce yellow-colored floral nectar, but the chemical identity and biological function of the yellow pigment are unknown. A combination of analytical biochemistry techniques was used to identify the pigment that gives Capsicum baccatum and Capsicum pubescens nectars their yellow color. Microbial growth assays, visual modeling, and honey bee preference tests for artificial nectars containing riboflavin were used to assess potential biological roles for the nectar pigment. High concentrations of riboflavin (vitamin B2) give the nectars their intense yellow color. Nectars containing riboflavin generate reactive oxygen species when exposed to light and reduce microbial growth. Visual modeling also indicates that the yellow color is highly conspicuous to bees within the context of the flower. Lastly, field experiments demonstrate that honey bees prefer artificial nectars containing riboflavin. Some Capsicum nectars contain a yellow-colored vitamin that appears to play roles in (1) limiting microbial growth, (2) the visual attraction of bees, and (3) as a reward to nectar-feeding flower visitors (potential pollinators), which is especially interesting since riboflavin is an essential nutrient for brood rearing in insects. These results cumulatively suggest that the riboflavin found in some Capsicum nectars has several functions.

Identification and evaluation of Escherichia coli strain ATCC 8739 as a surrogate for thermal inactivation of enterohemorrhagic Escherichia coli in fruit nectars: Impact of applied techniques on the decimal reduction time.

The objective of this study was to identify a suitable surrogate for E. coli O157:H7 strain 19685/91 and O113:H21 strain TS18/08, by assessing their thermal resistance at temperatures of 60 °C, 65 °C, and 72 °C in strawberry nectar. The influence of the matrix and the research methodology on the decimal reduction time (D-value) was investigated. Thermal kinetics and safety assessment demonstrated that E. coli ATCC 8739 is a suitable surrogate. The study demonstrated that the presence of fruit particles in the nectar increased thermal resistance of the tested strains. Variations in D-values were observed depending on the research method employed, with D-values in glass capillaries were up to 6.6 times lower compared to larger sample volumes. Encapsulation of E. coli ATCC 8739 exhibited high efficiency of 90.25 ± 0.26% and maintained stable viable counts after 26 days of storage in strawberry nectar at 4 °C. There were no significant differences in thermal resistance between surrogates directly inoculated into strawberry nectar and those encapsulated in alginate beads. Additionally, the encapsulated strains did not migrate outside the beads. Therefore, encapsulated E. coli ATCC 8739 in alginate beads can be effectively utilized in industrial settings to validate thermal treatments as a reliable and safe method.

Feeding efficiency of two coexisting nectarivorous bat species (Phyllostomidae: Glossophaginae) at flowers of two key-resource plants.

Animals should maximize their energy uptake while reducing the costs for foraging. For flower-visitors these costs and benefits are rather straight forward as the energy uptake equals the caloric content of the consumed nectar while the costs equal the handling time at the flower. Due to their energetically demanding lifestyle, flower-visiting bats face particularly harsh energetic conditions and thus need to optimize their foraging behavior at the flowers of the different plant species they encounter within their habitat. In flight cage experiments we examined the nectar-drinking behavior (i.e. hovering duration, nectar uptake, and the resulting feeding efficiency) of the specialized nectar-feeding bat Hylonycteris underwoodi and the more generalistic Glossophaga commissarisi at flowers of two plant species that constitute important nectar resources in the Caribbean lowland rainforests of Costa Rica and compared nectar-drinking behavior between both bat species and at both plant species. We hypothesized that the 1) specialized bat should outperform the more generalistic species and that 2) bats should generally perform better at flowers of the nectar-rich flowers of the bromeliad Werauhia gladioliflora than at the relatively nectar-poor flowers of the Solanaceae Merinthopodium neuranthum that has an extremely long flowering phase and therefore is an extremely reliable nectar resource, particularly for the specialized Hylonycteris. While we did not find substantial differences in the feeding efficiency of the generalist G. commissarisi, we observed an increased feeding efficiency of the specialized H. underwoodi at flowers of the nectar-poor M. neuranthum. This suggests that familiarity and ecological importance are more important determinants of the interaction than just morphological traits. Our results demonstrate that in addition to morphology, behavioral adaptations are also important drivers that determine the fitness of nectar-feeding bats. Both familiarity with and the ecological importance of a resource seem to contribute to shaping the interactions between pollinating bats and their plants.

Nectar and floral morphology differ in evolutionary potential in novel pollination environments.

Plants can evolve rapidly after pollinator changes, but the response of different floral traits to novel selection can vary. Floral morphology is often expected to show high integration to maintain pollination accuracy, while nectar traits can be more environmentally sensitive. The relative role of genetic correlations and phenotypic plasticity (PP) in floral evolution remains unclear, particularly for nectar traits, and can be studied in the context of recent pollinator changes. Digitalis purpurea shows rapid recent evolution of corolla morphology but not nectar traits following a range expansion with hummingbirds added as pollinators. We use this species to compare PP, heritability, evolvability and integration of floral morphology and nectar in a common garden. Morphological traits showed higher heritability than nectar traits, and the proximal section of the corolla, which regulates access to nectar and underwent rapid change in introduced populations, presented lower integration than the rest of the floral phenotype. Nectar was more plastic than morphology, driven by highly plastic sugar concentration. Nectar production rate showed high potential to respond to selection. These results explain the differential rapid evolution of floral traits previously observed in this species and show how intrafloral modularity determines variable evolutionary potential in morphological and nectar traits.

Gamma-aminobutyric acid in flower nectar and its possible physiological and behavioral effects on insect pollinators.

Floral nectar, a vital nutrition source for pollinators, contains diverse chemical compounds, including γ-aminobutyric acid (GABA), a prevalent nonproteinogenic amino acid. While GABA's physiological role is known and well-studied, its ecological significance in plant-pollinator interactions remains unclear. Recent studies on GABA's effects on pollinators' preference, consumption, survival, physiology, and behavior show varying outcomes according to the species, indicating a complex relationship. GABA consumption impacts motor function and cognitive abilities, potentially influencing pollination efficiency. Future research addressing diverse concentrations, species, and behavioral aspects is crucial for comprehensively understanding GABA's ecological role in plant-pollinator interactions.

Convergent evolution of fern nectaries facilitated independent recruitment of ant-bodyguards from flowering plants.

Plant-herbivore interactions reciprocally influence species' evolutionary trajectories. These interactions have led to many physical and chemical defenses across the plant kingdom. Some plants have even evolved indirect defense strategies to outsource their protection to ant bodyguards by bribing them with a sugary reward (nectar). Identifying the evolutionary processes underpinning these indirect defenses provide insight into the evolution of plant-animal interactions. Using a cross-kingdom, phylogenetic approach, we examined the convergent evolution of ant-guarding nectaries across ferns and flowering plants. Here, we discover that nectaries originated in ferns and flowering plants concurrently during the Cretaceous, coinciding with the rise of plant associations in ants. While nectaries in flowering plants evolved steadily through time, ferns showed a pronounced lag of nearly 100 My between their origin and subsequent diversification in the Cenozoic. Importantly, we find that as ferns transitioned from the forest floor into the canopy, they secondarily recruited ant bodyguards from existing ant-angiosperm relationships.

Shining a light on UV-fluorescent floral nectar after 50 years.

Nature is aglow with numerous captivating examples of UV-fluorescence in the animal kingdom. Despite a putative role as a visual signal, exploration of UV-fluorescence in plants and its role in plant-animal interactions is lagging in comparison. Almost 50 years ago, UV-fluorescence of floral nectar, a crucial reward for pollinators, was reported for 23 flowering plant species. Since this intriguing discovery, UV-fluorescent nectar has only seldom been addressed in the scientific literature and has not been scrutinized in a phylogenetic or ecological context. Here, we report the prevalence of vibrant UV-fluorescent floral nectar across the family Cleomaceae, including the first photographic documentation in vivo colour for flowering plants. Though Cleomaceae flowers are morphologically diverse varying in colour, nectary prominence, and nectar volume, UV-fluorescent floral nectar may be a ubiquitous characteristic of the family. Fluorescence spectra show that the identity and number of fluorescent compounds in floral nectar may differ among Cleomaceae species. As Cleomaceae pollinators range from insects to bats and birds, we suggest that the UV-fluorescent floral nectar not only functions as a visual cue for the diurnal pollinators but also for the nocturnal/crepuscular pollinators in low light settings.

Ultrastructure and development of the floral nectary from Borago officinalis L. and phytochemical changes in its secretion.

Although Boraginaceae have been classified as good sources of nectar for many insects, little is still known about their nectar and nectaries. Thus, in the present contribution, we investigated the nectar production dynamics and chemistry in Borago officinalis L. (borage or starflower), together with its potential interaction capacity with pollinators. A peak of nectar secretion (∼5.1 µL per flower) was recorded at anthesis, to decrease linearly during the following 9 days. In addition, TEM and SEM analyses were performed to understand ultrastructure and morphological changes occurring in borage nectary before and after anthesis, but also after its secretory phase. Evidence suggested that nectar was transported by the apoplastic route (mainly from parenchyma to epidermis) and then released essentially by exocytotic processes, that is a granulocrine secretion. This theory was corroborated by monitoring the signal of complex polysaccharides and calcium, respectively, via Thiéry staining and ESI/EELS technique. After the secretory phase, nectary underwent degeneration, probably through autophagic events and/or senescence induction. Furthermore, nectar (Nec) and other flower structures (i.e., sepals, gynoecia with nectaries, and petals) from borage were characterized by spectrophotometry and HPLC-DAD, in terms of plant secondary metabolites, both at early (E-) and late (L-) phase from anthesis. The content of phytochemicals was quantified and discussed for all samples, highlighting potential biological roles of these compounds in the borage flower (e.g., antimicrobial, antioxidant, staining effects). Surprisingly, a high significant accumulation of flavonoids was registered in L-Nec, with respect to E-Nec, indicating that this phenomenon might be functional and able to hide molecular (e.g., defence against pathogens) and/or ecological (e.g., last call for pollinators) purposes. Indeed, it is known that these plant metabolites influence nectar palatability, encouraging the approach of specialist pollinators, deterring nectar robbers, and altering the behaviour of insects.

Following Regulation, Imidacloprid Persists and Flupyradifurone Increases in Nontarget Wildlife.

After regulation of pesticides, determination of their persistence in the environment is an important indicator of effectiveness of these measures. We quantified concentrations of two types of systemic insecticides, neonicotinoids (imidacloprid, acetamiprid, clothianidin, thiacloprid, and thiamethoxam) and butenolides (flupyradifurone), in off-crop nontarget media of hummingbird cloacal fluid, honey bee (Apis mellifera) nectar and honey, and wildflowers before and after regulation of imidacloprid on highbush blueberries in Canada in April 2021. We found that mean total pesticide load increased in hummingbird cloacal fluid, nectar, and flower samples following imidacloprid regulation. On average, we did not find evidence of a decrease in imidacloprid concentrations after regulation. However, there were some decreases, some increases, and other cases with no changes in imidacloprid levels depending on the specific media, time point of sampling, and site type. At the same time, we found an overall increase in flupyradifurone, acetamiprid, thiamethoxam, and thiacloprid but no change in clothianidin concentrations. In particular, flupyradifurone concentrations observed in biota sampled near agricultural areas increased twofold in honey bee nectar, sevenfold in hummingbird cloacal fluid, and eightfold in flowers after the 2021 imidacloprid regulation. The highest residue detected was flupyradifurone at 665 ng/mL (parts per billion [ppb]) in honey bee nectar. Mean total pesticide loads were highest in honey samples (84 ± 10 ppb), followed by nectar (56 ± 7 ppb), then hummingbird cloacal fluid (1.8 ± 0.5 ppb), and least, flowers (0.51 ± 0.06 ppb). Our results highlight that limited regulation of imidacloprid does not immediately reduce residue concentrations, while other systemic insecticides, possibly replacement compounds, concurrently increase in wildlife. Environ Toxicol Chem 2024;43:1497-1508. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.