Nectar Feeding Research Articles

¿Quién poliniza realmente los agaves? Diversidad de visitantes florales en 3 especies de Agave (Agavoideae: Asparagaceae)

Activity patterns of inflorescence visitors are described for 3 species of Agave: Agave difformis, A. garciae-mendozae and A. striata from different sites at Barranca de Metztitlán, Hidalgo, Mexico. The potential role of the visitors in the pollination process was defined: pollen or nectar robbers, or as primary or secondary pollinators, secondary if they visit less flowers or do so in an inefficient way. Visitor's activity was recorded for 24 consecutive hours on 5 inflorescences. The visitors were from the following groups: hawkmoths, bats, bees and hummingbirds. The peak of the activity in the 3 Agave species was registered between 21:00 to 03:00h. In some cases, diurnal visitors (bees and hummingbirds) could also be pollinators. The primary pollinators were the nectar feeding bats Leptonycteris yerbabuenae, L. nivalis, and Choeronycteris mexicana. The most common secondary pollinator was the hawkmoth Erinnyis ello. The main pollen and nectar robber was the European honey bee, Apis mellifera, however, A. mellifera could also be considered as a secondary pollinator for A. striata, because this species has smaller flowers.

Predatory hoverflies increase oviposition in response to colour stimuli offering no reward: Implications for biological control

There are increasing efforts worldwide to engineer agroecosystems to enhance ecosystem services such as carbon storage, minimisation of erosion, and biological control of pests. A key group of insect biological control agents is the hoverflies (Diptera: Syrphidae). While adult Syrphidae are pollen and nectar feeders, the larvae of many species are aphidophagous, thus demonstrating life-history omnivory and their potentially important role in the biological control of aphids and other pests. Several experiments have been conducted to assess whether the presence of flowers in or near crops has an effect on oviposition by syrphids, but the results have often been inconclusive. This paper describes a large-scale field experiment carried out over two years, in which standardised model flowers were placed in field margins and oviposition rates monitored near them. Statistically significantly more eggs were laid on broad bean (Vicia faba) infested with the pea aphid, Acyrthosiphon pisum, near yellow model flowers with and without pollen and honey resources than at positions with no model flowers nearby. These results suggest strongly that the presence of model flowers increases hoverfly oviposition and that colour may be more important than food resources in enhancing this behaviour. This work indicates that biological control of pests by hoverflies can be enhanced by simple, non-floral agroecological interventions.

Nectar feeding behavior of some butterflies in the botanical garden of Dhaka university

Nectar feeding behavior of butterflies belonging to the families Nymphalidae, Danaidae, Pieridae, Lycaenidae and Papilionidae were studied in the Botanical garden of Dhaka University. The highest and the lowest duration of searching time was 39 ± 2 and 36 ± 5 seconds respectively for the Catopsila pomona and Zizina otis. The highest and the lowest duration of feeding was 13.0 ± 1 and 9.9 ± 0.9 seconds respectively for the Danaus chrysippus and Zizina otis. The longest proboscis (12.6 ± mm) was recorded in Danaus chrysipus. The deepest corolla (22 ± 5mm) was found in the flower of Cosmos bipinnatus plants. The proboscis of 4 butterfly species named Eurema hecabe, Jononia almana, Catochrysopes strabo and D. chrysipus was highly correlated with the corolla tube of Cosmos bipinnatus, Tephrosia purpurea and Tagetes erecta repectively.Bangladesh J. Zool. 42(1): 85-90, 2014

Rapid nectar-meal effects on a predator's capacity to kill mosquitoes.

Using Evarcha culicivora, an East African jumping spider (Salticidae), we investigate how nectar meals function in concert with predation specifically at the juvenile stage between emerging from the egg sac and the first encounter with prey. Using plants and using artificial nectar consisting of sugar alone or sugar plus amino acids, we show that the plant species (Lantana camara, Ricinus communis, Parthenium hysterophorus), the particular sugars in the artificial nectar (sucrose, fructose, glucose, maltose), the concentration of sugar (20%, 5%, 1%) and the duration of pre-feeding fasts (3 days, 6 days) influence the spider's prey-capture proficiency on the next day after the nectar meal. However, there were no significant effects of amino acids. Our findings suggest that benefits from nectar feeding are derived primarily from access to particular sugars, with fructose and sucrose being the most beneficial, glucose being intermediate and maltose being no better than a water-only control.

Temporal Variation in the Behavior ofApis mellifera(Hymenoptera: Apidae) andLycastrirhyncha nitens(Diptera: Syrphidae) onPontederia sagittata(Commelinales: Pontederiaceae) Inflorescences in Relation to Nectar Availability

Insect-pollinated plants offer nectar as the main reward, which influences the preference of flower visitors. We describe the feeding behavior of the exotic bee Apis mellifera (L.) (Hymenoptera: Apidae) and the flower fly Lycastrirhyncha nitens (Bigot) (Diptera: Syrphidae) on tristylous flowers of Pontederia sagittata (C. Presl) (Commelinales: Pontederiaceae) in relation to temporal nectar availability. The production of this resource was similar between floral morphs but there were temporal variations during the anthesis period, in a coincidence with a higher number of visitors and activity of bees and flies. The dynamics of nectar production could be related to the feeding behavior of these insects despite the similarity in daily nectar volume produced in all the 3 types of flowers. The variations of nectar feeding may affect the transportation of pollen among the 3 floral morphs.

Erection pattern and section-wise wettability of honeybee glossal hairs in nectar feeding.

The honeybee's tongue (glossa) is covered with bushy hairs and resembles a mop or a brush. We examined the dimensions of glossal hairs of the Italian honeybee (Apis mellifera ligustica) and found that the average length of hairs increased from the proximal segment to the distal end. The glossal dynamic surface of a honeybee in drinking cycles was captured by a specially designed high-speed camera system, and we discovered that the glossal hairs erected rhythmically when drinking nectar; specifically, hairs on the proximal segment erected earlier than those on the distal end of a honeybee's tongue, which was identified as the phenomenon of asynchronous hair erection. Moreover, by measuring the wettability of the tongue, we found that the flabellum was the most hydrophilic and the root of the tongue was hardest to be wetted. According to our observations, we suggest that the honeybee has an optimal hair-erection pattern that could balance nectar intake and viscous drag. These results will be helpful to understand the liquid-feeding mechanism of honeybees, especially the role of erectable glossal hairs.

Switchable Wettability of the Honeybee's Tongue Surface Regulated by Erectable Glossal Hairs.

Various nectarivorous animals apply bushy-hair-equipped tongues to lap nectar from nectaries of flowers. A typical example is provided by the Italian honeybee (Apis mellifera ligustica), who protracts and retracts its tongue (glossa) through a temporary tube, and actively controls the erectable glossal hairs to load nectar. We first examined the microstructure of the honeybee’s glossal surface, recorded the kinematics of its glossal hairs during nectar feeding process and observed the rhythmical hair erection pattern clearly. Then we measured the wettability of the glossal surface under different erection angles (EA) in sugar water of the mass concentration from 25 to 45%, mimicked by elongating the glossa specimens. The results show that the EA in retraction approximately remains stable under different nectar concentrations. In a specific concentration (35, 45, or 55%), the contact angle decreases and glossal surface area increases while the EA of glossal hairs rises, the glossa therefore could dynamically alter the glossal surface and wettability in foraging activities, not only reducing the energy consumption for impelling the nectar during tongue protraction, but also improving the nectar-trapping volume for feeding during glossa retraction. The dynamic glossal surface with switchable wettability regulated by erectable hairs may reveal the effective adaptation of the honeybee to nectar intake activities.

Evolution of extreme proboscis lengths in Neotropical Hesperiidae (Lepidoptera)

Exaggerated morphologies have evolved in insects as adaptations to nectar feeding by natural selection. For example, the suctorial mouthparts of butterflies enable these insects to gain access to floral nectar concealed inside deep floral tubes. Proboscis length in Lepidoptera is known to scale with body size, but whether extreme absolute proboscis lengths of nectar feeding butterflies result from a proportional or disproportional increase with body size that differs between phylogenetic lineages remains unknown. We surveyed the range of variation that occurs in scaling relationships between proboscis length and body size against a phylogenetic background among Costa Rican Hesperiidae. We obtained a new record holder for the longest proboscis in butterflies and showed that extremely long proboscides evolved at least three times independently within Neotropical Hesperiidae. We conclude that the evolution of extremely long proboscides results from allometric scaling with body size, as demonstrated in hawk moths. We hypothesize that constraints on the evolution of increasingly long butterfly proboscides may come from (1) the underlying scaling relationships, i.e., relative proboscis length, combined with the butterfly's flight style and flower-visiting behaviour and/or (2) developmental constraints during the pupal phase. Lastly, we discuss why butterflies did not evolve similar scaling relationships as hawk moths.

The makings of a powerful sweet tooth

The main attraction of nectar, a hummingbird favorite, is the sweet taste of sugar. Oddly, though, birds lack the main vertebrate receptor for sweet taste, T1R2. Baldwin et al. show that a related receptor, T1R1-T1R3, which generally controls savory taste in vertebrates, adapts in hummingbirds to detect sweet (see the Perspective by Jiang and Beauchamp). This repurposing probably allowed hummingbirds to specialize in nectar feeding and may have assisted the evolution of the many and varied hummingbird species seen today. M. W. Baldwin, Y. Toda, T. Nakagita, M. J. O’Connell, K. C. Klasing, T. Misaka, S. V. Edwards, S. D. Liberles, Evolution of sweet taste perception in hummingbirds by transformation of the ancestral umami receptor. Science 345 , 929–933 (2014). [Abstract][Full Text] P. Jiang, G. K. Beauchamp, Sensing nectar’s sweetness. Science 345 , 878–879 (2014). [Abstract][Full Text]

Sensory biology. Evolution of sweet taste perception in hummingbirds by transformation of the ancestral umami receptor.

Sensory systems define an animal's capacity for perception and can evolve to promote survival in new environmental niches. We have uncovered a noncanonical mechanism for sweet taste perception that evolved in hummingbirds since their divergence from insectivorous swifts, their closest relatives. We observed the widespread absence in birds of an essential subunit (T1R2) of the only known vertebrate sweet receptor, raising questions about how specialized nectar feeders such as hummingbirds sense sugars. Receptor expression studies revealed that the ancestral umami receptor (the T1R1-T1R3 heterodimer) was repurposed in hummingbirds to function as a carbohydrate receptor. Furthermore, the molecular recognition properties of T1R1-T1R3 guided taste behavior in captive and wild hummingbirds. We propose that changing taste receptor function enabled hummingbirds to perceive and use nectar, facilitating the massive radiation of hummingbird species.

One proboscis, two tasks: Adaptations to blood-feeding and nectar-extracting in long-proboscid horse flies (Tabanidae, Philoliche)

Female Pangoniinae in the tabanid fly genus Philoliche can display remarkably elongated proboscis lengths, which are adapted for both blood- and nectar-feeding. Apart from their role as blood-sucking pests, they represent important pollinators of the South African flora. This study examines the morphology of the feeding apparatus of two species of long-proboscid Tabanidae: Philoliche rostrata and Philoliche gulosa – both species display adaptations for feeding from a diverse guild of long-tubed flowers, and on vertebrate blood. The heavily sclerotised proboscis can be divided into two functional units. The short, proximal piercing part is composed of the labrum-epipharynx unit, the hypopharynx and paired mandible and maxilla. The foldable distal part is composed of the prementum of the labium which solely forms the food canal and is responsible for nectar uptake via the apical labella. The proboscis works as a drinking straw, relying on a pressure gradient provided by a two-part suction pump in the head. Both proboscis and body lengths and suction pump dimensions show a significantly correlated allometric relationship with each other. This study provides detailed insights into the adaptations for a dual diet using an elongated sucking proboscis, and considers these adaptations in the context of the evolution of nectar feeding in Brachycera.

SELECTION FOR MECHANICAL ADVANTAGE UNDERLIES MULTIPLE CRANIAL OPTIMA IN NEW WORLD LEAF-NOSED BATS

Selection for divergent performance optima has been proposed as a central mechanism underlying adaptive radiation. Uncovering multiple optima requires identifying forms associated with different adaptive zones and linking those forms to performance. However, testing and modeling the performance of complex morphologies like the cranium is challenging. We introduce a three-dimensional finite-element (FE) model of the cranium that can be morphed into different shapes by varying simple parameters to investigate the relationship between two engineering-based measures of performance, mechanical advantage and von Mises stress, and four divergent adaptive zones occupied by New World Leaf-nosed bats. To investigate these relationships, we tested the fit of Brownian motion and Ornstein-Uhlenbeck models of evolution in mechanical advantage and von Mises stress using dated multilocus phylogenies. The analyses revealed three performance optima for mechanical advantage among species from three adaptive zones: bats that eat nectar; generalized insectivores, omnivores and some frugivores; and bats that specialize on hard canopy fruits. Only two optima, one corresponding to nectar feeding, were consistently uncovered for von Mises stress. These results suggest that mechanical advantage played a larger role than von Mises stress in the radiation of New World Leaf-nosed bats into divergent adaptive zones.

Foraging Behavior of Apis Mellifera (Hymenoptera: Apidae) and Lycastrirhyncha Nitens (Diptera: Syrphidae) onPontederia sagittata(Commelinales: Pontederiaceae) on a Disturbed Site

By influencing the exchange of pollen, floral visitor behavior largely promotes the reproductive success of the plants. Pontederia sagittata (C. Presl) (Commelinales: Pontederiaceae) is a tristylous species whose morphs (long-styled L, mid-styled M and short-styled S) differ in the arrangement of reproductive organs and the amounts and accessibility for food for pollinating insects. We evaluated the behavior of 2 common contemporary visitors to inflorescences, the exotic bee Apis mellifera (L.) (Apidae), a not historical pollinator, and the flower fly Lycastrirhyncha nitens (Bigot) (Syrphidae), a frequent visitor already reported on this aquatic plant, based on HD video records of the number of individuals and the frequency and duration of their visits to 300 inflorescences. Both species of insects preferred to visit S-morph inflorescences. Pollen collection and nectar feeding were the most important activities of the bees, whereas flower flies were observed fed only on nectar. Thus, these behaviors could play an important role in reproduction in the study population of P. sagittata.

Resource defense and monopolization in a marked population of ruby‐throated hummingbirds (Archilochus colubris)

Resource defense behavior is often explained by the spatial and temporal distribution of resources. However, factors such as competition, habitat complexity, and individual space use may also affect the capacity of individuals to defend and monopolize resources. Yet, studies frequently focus on one or two factors, overlooking the complexity found in natural settings. Here, we addressed defense and monopolization of nectar feeders in a population of free-ranging ruby-throated hummingbirds marked with passive integrated transponder (PIT tags). Our study system consisted of a 44 ha systematic grid of 45 feeders equipped with PIT tag detectors recording every visit made at feeders. We modeled the number of visits by competitors (NVC) at feeders in response to space use by a focal individual potentially defending a feeder, number of competitors, nectar sucrose concentration, and habitat visibility. Individuals who were more concentrated at certain feeders on a given day and who were more stable in their use of the grid throughout the season gained higher exclusivity in the use of those feeders on that day, especially for males competing against males. The level of spatial concentration at feeders and its negative effect on NVC was, however, highly variable among individuals, suggesting a continuum in resource defense strategies. Although the apparent capacity to defend feeders was not affected by competition or nectar sucrose concentration, the level of monopolization decreased with increasing number of competitors and higher nectar quality. Defense was enhanced by visibility near feeders, but only in forested habitats. The reverse effect of visibility in open habitats was more difficult to interpret as it was probably confounded by perch availability, from which a bird can defend its feeder. Our study is among the first to quantify the joint use of food resource by overlapping individuals unconstrained in their use of space. Our results show the importance of accounting for variation in space use among individuals as it translated into varying levels of defense and monopolization of feeders regardless of food resource distribution.

Nectar Feeding Habits of Loten’s Sunbird Cinnyris lotenius and Purple-rumped Sunbird Leptocoma zeylonica in the Royal Botanical Gardens, Peradeniya, Sri Lanka

Sunbirds (Nectariniidae) are small passerines that feed largely on nectar. The aim of thiswork was to observe the relationship of the purple-rumped sunbird Leptocoma zeylonica andLoten’s sunbird Cinnyris lotenius with their host flowers, and to examine their relationshipwith the glucose concentration of nectar, flower count and the length of corolla. The studywas carried out in the Royal Botanical Gardens, Peradeniya, Sri Lanka, between February2013 and September 2013. For each observation, plant species visited for nectar feeding,method of obtaining food, glucose concentration of nectar, length of corolla, and flower countwere recorded. Both species of sunbirds visited Hamelia patens, Sanchezia speciosa,Heliconia rostrata, Megaskepasma erythrochlamys, Strobilanthes flaccidifolius,Graptophyllum pictum and Pachystachys spicata. The male Loten’s sunbird’s occurrence ona given flower is biased by the presence of female (Pearson correlation coefficient: 0.874; PValue:<0.001). The Purple-rumped female’s occurrence is biased by the presence of male(Pearson correlation coefficient: 0.819; P-Value: <0.001). The results also indicated that therewas no significant correlation between the occurrence of the bird and the glucoseconcentration of the flower (Pearson correlation coefficients: -0.045; P-Value: 0.740;[Loten’s male]; -0.094; P-Value: 0.489; [Loten’s female]; -0.061; P-Value: 0.653; [Purplerumpedmale]; 0.001; P-Value: 0.997; [Purple-rumped female]). Similarly, there was nosignificant correlation between the flower count with the occurrence of the bird (Pearsoncorrelation coefficients: 0.160; P-Value: 0.239; [Loten’s male], 0.171; P-Value: 0.208;[Loten’s female]; 0.172; P-Value: 0.595; [Purple rumped male]; 0.211; P-Value: 0.118;[Purple-rumped female]). The Loten’s sunbird has no significant correlation with flowercorolla length (Pearson correlation coefficients: -0.240; P-Value: 0.075; [Loten’s male]; -0.142; P-Value: 0.297; [Loten’s female]). The Purple-rumped sunbird has a significantcorrelation with the flower corolla length. (Pearson correlation coefficient: -0.399; P-Value:0.020; [Purple rumped male]; -0.452; P-Value: <0.001; [Purple-rumped female]). Dependingon the length of corolla, the nectar obtaining method varied as probing or piercing.

Nectar feeding by weavers (Ploceidae) and their role as pollinators

Reviews of nectar-feeding by birds initially focused on specialist nectarivores and ignored the role that more generalist feeders may play in plant pollination. Recent work has emphasised the range of bird species, both specialist and opportunistic, that feed on nectar. In this review, I collate published information on nectar-feeding by weavers, highlight known weaver–plant relationships, and suggest areas for future research. There are published records of nectar feeding for Plocepasser superciliosus, Amblyospiza albifrons, Anaplectes rubriceps, two Quelea spp., four Euplectes spp., all six Foudia spp., two Malimbus spp. and 22 Ploceus spp. To date, there have been no unambiguous reports of other genera feeding on nectar. The role of Ploceus species as pollinators of Strelitzia reginae, proposed by ornithologists decades ago, has recently been confirmed by botanists. Current studies of Aloe species in South Africa suggest that opportunistic avian nectarivores such as ploceids may be the chief pollinators of bird-pollinated plants in this genus, whereas specialist nectar feeders (sunbirds) may be ‘nectar robbers’ in many cases. Particularly for winter-flowering plants, weaver species are potential pollinators, but exclusion experiments are needed to establish their role, while the dietary importance of nectar, and its impact on the birds’ physiology, has not been critically studied.

Trophic niche flexibility in Glossophaga soricina: how a nectar seeker sneaks an insect snack

Summary Omnivory enables animals to fill more than one trophic niche, providing access to a wider variety of food resources with potentially higher nutrient value, particularly when resources become scarce. Animals can achieve omnivory using different strategies, for example opportunistic foraging, or switching between multiple trophic niches. The Neotropical bat Glossophaga soricina (Pallas, 1766) is a common and widespread species known for nectar feeding, but it also eats fruit and insects. Approaching stationary objects (flowers and fruits) or moving objects (insects) poses different sensory tasks and should require different echolocation behaviours. Here we tested the contrasting hypothesis that G. soricina can approach both stationary and moving objects using the same echolocation behaviour, thus feeding at different trophic levels by a single sensory mechanism. Using DNA barcoding, we demonstrate that G. soricina eats beetles (Coleoptera), flies (Diptera) and noctuid moths with bat‐detecting ears. Laboratory observations show that G. soricina actively hunts for prey so insect consumption does not appear to be opportunistic. After capture, individuals consumed prey while perched and manipulated them with jaw, thumb, wrist and wing movements, but food handling was longer and chewing rate slower than in obligate insectivores. In contrast to most insectivorous bats, the echolocation calls of G. soricina are of high frequency and low intensity, and G. soricina did not produce feeding buzzes when approaching insects. An acoustic model of detection distances shows that its low‐intensity calls fail to trigger the auditory neurons of eared moths, allowing G. soricina to overcome auditory prey defences. Individuals achieved niche flexibility using a unique but generalist behavioural approach rather than employing two different specialist methods. Our findings provide a novel insight into the functional mechanisms of insect capture in G. soricina and highlight the importance of considering niche flexibility in classifying trophic links in ecological communities.

Mice feeding on Sarracenia secretion

This story started a couple of years back when I arrived at my New Zealand greenhouse and found a pair of native nectar feeding birds we call wax eyes (Zosterops lateralis) flying along the inside of the greenhouse and hanging around a group of autumn Sarracenia leucophylla pitchers. I managed to take a couple of very average photos of the wax eyes feeding from the mouths of the S. leucophylla.

Time management and nectar flow: flower handling and suction feeding in long-proboscid flies (Nemestrinidae: Prosoeca)

A well-developed suction pump in the head represents an important adaptation for nectar-feeding insects, such as Hymenoptera, Lepidoptera and Diptera. This pumping organ creates a pressure gradient along the proboscis, which is responsible for nectar uptake. The extremely elongated proboscis of the genus Prosoeca (Nemestrinidae) evolved as an adaptation to feeding from long, tubular flowers. According to the functional constraint hypothesis, nectar uptake through a disproportionately elongated, straw-like proboscis increases flower handling time and consequently lowers the energy intake rate. Due to the conspicuous length variation of the proboscis of Prosoeca, individuals with longer proboscides are hypothesised to have longer handling times. To test this hypothesis, we used field video analyses of flower-visiting behaviour, detailed examinations of the suction pump morphology and correlations of proboscis length with body length and suction pump dimensions. Using a biomechanical framework described for nectar-feeding Lepidoptera in relation to proboscis length and suction pump musculature, we describe and contrast the system in long-proboscid flies. Flies with longer proboscides spent significantly more time drinking from flowers. In addition, proboscis length and body length showed a positive allometric relationship. Furthermore, adaptations of the suction pump included an allometric relationship between proboscis length and suction pump muscle volume and a combination of two pumping organs. Overall, the study gives detailed insight into the adaptations required for long-proboscid nectar feeding, and comparisons with other nectar-sucking insects allow further considerations of the evolution of the suction pump in insects with sucking mouthparts.Electronic supplementary materialThe online version of this article (doi:10.1007/s00114-013-1114-6) contains supplementary material, which is available to authorized users.

Volatile phytochemicals as mosquito semiochemicals

Plant biochemical processes result in the release of an array of volatile chemical substances into the environment, some of which are known to play important plant fitness enhancing functions, such as attracting pollinators, thermal tolerance of photosynthesis, and defense against herbivores. Cunningly, phytophagous insects have evolved mechanisms to utilize these volatiles to their own advantage, either to colonize a suitable host for feeding, reproduction and oviposition or avoid an unsuitable one. The volatile compounds involved in plant–insect chemical interactions have been widely exploited in the management of agricultural pests. On the other hand, use of plant volatiles in the management of medically important insects is limited, mainly due to paucity of information on their role in disease vector–plant interactions. To date, a total of 29 plant volatile compounds from various chemical classes, including phenols, aldehydes, alcohols, ketones and terpenes, have been identified as mosquito semiochemicals. In this review, we present highlights of mosquito–plant interactions, the available evidence of nectar feeding, with particular emphasis on sources of plant attractants, methods of plant volatile collection and the candidate plant volatile compounds that attract mosquitoes to nectar sources. We also highlight the potential application of these phytochemical attractants in integrated mosquito management.