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222 results for “Nectar”

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dryad36/100

Deep learning object detection to estimate the nectar sugar mass of flowering vegetation

Floral resources are a key driver of pollinator abundance and diversity, yet their quantification in the field and laboratory is laborious and requires specialist skills. Using a dataset of 25000 labelled tags of fieldwork-realistic quality, a Convolutional Neural Network (Faster R-CNN) was trained to detect the nectar-producing floral units of 25 taxa in surveyors' quadrat images of native, weed-rich grassland in the UK. Floral unit detection on a test set of 50 model-unseen images of comparable vegetation returned a precision of 90%, recall of 86% and F1 score (the harmonic mean of precision and recall) of 88%. Model performance was consistent across the range of floral abundance in this habitat. Comparison of the nectar sugar mass estimates made by the CNN and three human surveyors returned similar means and standard deviations. Over half of the nectar sugar mass estimates made by the model fell within the absolute range of those of the human surveyors. The optimal number of quadrat image samples was determined to be the same for the CNN as for the average human surveyor. For a standard quadrat sampling protocol of 10–15 replicates, this application of deep learning could cut pollinator-plant survey time per stand of vegetation from hours to minutes. The CNN is restricted to a single view of a quadrat, with no scope for manual examination or specimen collection, though in contrast to human surveyors its object detection is deterministic and floral unit definition is standardised. As agri-environment schemes move from prescriptive to results-based, this approach provides an independent barometer for grassland management which is usable by both landowner and scheme administrator. The model can be adapted to visual estimations of other ecological resources such as winter bird food, floral pollen volume, insect infestation and tree flowering/fruiting, and by adjustment of classification threshold may show acceptable taxonomic differentiation for presence-absence surveys.

opencc-zeroAug 2021View details →

dryad36/100

Bumblebees' food preferences are jointly shaped by rapid valuation of nectar sugar concentration and viscosity

Animals are often assumed to follow a strategy of energy maximisation, and therefore should evaluate feeding options based on energy intake rates. Contrastingly, rhesus macaque's learned food preferences are based on sensory properties, e.g. sweetness and resistance, regardless of energy differences. Here, we show that nectar sugar concentration (sweetness) and nectar viscosity (resistance) drive preferences of bumblebees, classical models for economic and foraging decision-making. Using a tasteless/odourless biopolymer (tylose), we created feeding options that differed in sweetness and resistance, properties that affect energy intake rate and can be immediately sensed. When energy intake rates were similar, bumblebees developed preferences based on sweetness and resistance. When energy intake rates were different but sweetness and resistance were balanced against each other, bees developed no preferences. Decision dynamics during training indicated that bumblebees simultaneously evaluated sweetness and resistance to make decisions quickly (in seconds). These results indicate that bumblebees' food preferences are jointly affected by the immediate sensation of nectar sweetness and resistance as positively and negatively reinforcing properties, respectively, irrespective of energy intake rate. From these findings we propose that subjective valuations of sensory food properties should be considered as constraints in models of foraging behaviour.

opencc-zeroDec 2022View details →

dryad36/100

Impacts of neonicotinoid insecticides on bumble bee energy metabolism are revealed under nectar starvation

Bumble bees are an important group of insects that provide essential pollination services as a byproduct of their foraging behaviors. These pollination services are driven, in part, by energetic exchanges between flowering plants and individual bees. Thus, it is important to examine bumble bee energy metabolism and explore how it might be influenced by external stressors, which contribute to declines in global pollinator populations. Two stressors that are commonly encountered by bees include insecticides and nutritional stress. Our study examines the effects of neonicotinoid insecticide exposure alone, and in combination with nutritional stress, on bumble bee metabolism using a novel metabolomic approach. We hypothesized that exposure to the insecticide imidacloprid would disrupt bumble bee energy metabolism, leading to changes in key metabolites involved in energy metabolism. We exposed Bombus impatiens workers to imidacloprid according to one of three exposure paradigms designed to explore how sustained versus more limited imidacloprid exposure influences energy metabolites. After bees were exposed to imidacloprid, they were subjected to artificial nectar starvation. Our results showed that the strongest effects of imidacloprid were observed when treated bees also experienced artificial nectar starvation, suggesting a combinatorial effect of neonicotinoids and nutritional stress on energy metabolism. Overall, this study provides important insights into the mechanisms underlying the impact of neonicotinoid insecticides on bumble bees and underscores the need for further investigation into the complex interactions between environmental stressors and bee metabolism.

opencc-zeroApr 2023View details →

dryad36/100

Plant species with larger extrafloral nectaries produce better quality nectar only when needed and favour interactions with best ant partners

Few studies investigated the phenotypic plasticity of extrafloral nectary (EFN) functioning associated with indirect plant defense across species. Here, we experimentally investigate in three sympatric legume species the role of EFNs, hypothesizing that plant species with larger EFNs have higher induced nectar secretion after herbivory events, greater control over secretion, and are more likely to interact with more protective ant partners. We targeted 30 individuals of each legume species and estimated EFN size and activity in the field. We conducted field experiments to evaluate the phenotypic plasticity of nectar production after leaf damage and censused ant species feeding on EFNs. Plant species increased nectar after leaf damage but in different ways. Supporting our hypothesis, C. duckeana, with the largest EFNs, increased all nectar descriptors, taking its place as the most productive and intense post-herbivory induced response, attracting more dominant ants than the other plant species. The higher control over reward production in plant species with larger-sized EFN reflects an induction mechanism under damage that reduces costs and increases the potential benefits of indirect biotic defences. Together, these plant traits shape the patterns of ant attendance and defence against herbivores, possibly favouring the maintenance of plant protection mutualisms widespread in nature.

opencc-zeroApr 2023View details →

dryad36/100

A dataset of nectar sugar production for flowering plants found in urban greenspaces

<ol> <li>Nectar and pollen are floral resources that provide food for insect pollinators, so quantifying their supplies can help us to understand and mitigate pollinator declines. However, most existing datasets of floral resource measurements focus on native plants found in rural landscapes, so cannot be used effectively for estimating supplies in urban green spaces, where non-native ornamental plants often predominate.</li> <li>We sampled floral nectar sugar in 225 plant taxa found in UK residential gardens and other urban green spaces, focussing on the most common species. The vast majority (94%) of our sampled taxa are non-native, filling an important research gap and ensuring these data are also relevant outside of the UK.</li> <li>Our dataset includes values of daily nectar sugar production for all 225 taxa and nectar sugar concentration for around half (102) of those sampled. Nectar extraction was conducted according to published methods, ensuring our values can be combined with other datasets.</li> <li>We anticipate that the two main uses of these data are (1) to estimate the nectar production of habitats and landscapes, and (2) to identify high-nectar plants of conservation importance. To increase the utility of our data we provide guidance for scaling nectar values up from single flowers to floral units, as is commonly done in field studies.</li> </ol>

opencc-zeroMay 2023View details →

dryad36/100

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

Flower-visiting insects in agroecosystems forage on weeds exposed to agrochemicals that may compromise the quality of their floral resources. We conducted complementary field and greenhouse experiments to evaluate: 1) the effect of low concentrations of agrochemical exposure on nectar and pollen quality and 2) the relationship between floral resource quality and insect visitation. 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.

opencc-zeroMay 2023View details →

dryad36/100

Nectar robbing by bees affects the reproductive fitness of the distylous plant Tirpitzia sinensis (Linaceae)

Nectar robbing can affect plant reproductive success directly by influencing female and male fitness, and indirectly by affecting pollinator behavior. Flowers have morphological and chemical features that may protect them from nectar robbers. Previous studies on nectar robbing have focused mainly on homotypic plants. It remains unclear how nectar robbing affects the reproductive success of distylous plants, and whether defense strategies of two morphs are different. Nectar robbing rates on the long- and short- styled morph (L-morph, S-morph) of the distylous Tirpitzia sinensis were investigated. We compared floral traits, the temporal pattern of change in nectar volume and sugar concentration, nectar secondary metabolites and sugar composition between robbed and unrobbed flowers of two morphs. We tested direct effects of nectar robbing on female and male components of plant fitness and the indirect effects of nectar robbing via pollinators. Nectar robbing rates did not differ between the two morphs. Flowers with smaller sepals and petals were more easily robbed. The floral tube diameter and thickness were greater in L-morphs than in S-morphs, and the nectar rob holes were significantly smaller in L-morphs than in S-morphs. Nectar robbing significantly decreased nectar replenishment rate but did not affect nectar sugar concentration or sugar composition. After robbery the quantities and diversity of secondary compounds in the nectar of S-morphs increased significantly and the total relative contents of secondary compounds in L-morphs showed no obvious changes. Nectar robbing could decrease female fitness by decreasing pollen germination and thus decreasing seed set. Nectar robbing had no significant effects on male fitness. Robbed flowers were less likely to be visited by hawkmoth pollinators, especially in S-morphs. These results suggest that nectar robbing could directly and indirectly decrease the female fitness of T. sinensis, and different morphs have evolved different defense mechanisms in response to nectar robbing pressure.

opencc-zeroOct 2023View details →

ClinicalTrials.gov36/100

Neural Cardiac Therapy for Heart Failure Study (NECTAR-HF)

ClinicalTrials.gov study NCT01385176. IPD Sharing: NO. Countries: 8. Publications: 3.

closedIPD-NOFeb 2026View details →

ClinicalTrials.gov36/100

NECTAR Everolimus Plus Cisplatin in Triple (-) Breast Cancer

ClinicalTrials.gov study NCT01931163. IPD Sharing: Not stated. Countries: 1. Publications: 1.

restrictedIPD-UNDECIDEDFeb 2026View details →

dryad36/100