Search

Bees provide vital pollination services to the majority of flowering plants in both natural and agricultural systems. Unfortunately, both native and managed bee populations are experiencing declines, threatening the persistence of these plants and crops. Agricultural chemicals are one possible culprit contributing to bee declines. Even fungicides, generally considered safe for bees, have been shown to disrupt honey bee development and impair bumble bee behavior. Little is known, however, how fungicides may affect bumble bee colony growth. We conducted a controlled cage study to determine the effects of fungicide exposure on colonies of a native bumble bee species (Bombus impatiens). Colonies of B. impatiens were exposed to flowers treated with field-relevant levels of the fungicide chlorothalonil over the course of one month. Colony success was assessed by the number and biomass of larvae, pupae, and adult bumble bees. Bumble bee colonies exposed to fungicide produced fewer workers, lower total bee biomass, and had lighter mother queens than control colonies. Our results suggest that fungicides negatively affect the colony success of a native bumble bee species and that the use of fungicides during bloom has the potential to severely impact the success of native bumble bee populations foraging in agroecosystems. [ABSTRACT FROM AUTHOR]

Bumblebees integrate cues associated with food that they experience within their nest. Both experienced and naïve workers rely on odours in the nectar collected by foragers and stored in honeypots to gain information about currently available food sources. The ability of workers to retain memories of these odours and to orient towards them when they leave the nest affects both foraging efficiency and food yield for the colony. In this study, we added sugar solution containing a floral scent (i.e. training scent) directly to empty honeypots within nests of Bombus impatiens in the absence of all other stimuli normally associated with successful foragers. To assess bee learning and memory, we quantified the effects of (a) the number of exposures to the training scent during conditioning, (b) the number of days elapsed post-conditioning (3 days vs. 6 days) and (c) bee age, on appetitive choice of the training scent relative to an unfamiliar scent. A high proportion of the bees of all ages (i.e. 74–80%) contacted the scented syrup we supplied briefly to colonies, with most contacting it once but some as many as 14 times. Most of the bees that may have experienced the training scent in the hive atmosphere but failed to contact a honeypot containing the scented sucrose solution (i.e. bees for which the training scent was familiar but unrewarded) exhibited no response to either the familiar or unfamiliar scent; the few that responded had no preference for either scent. More frequent contact with the scented sucrose increased the likelihood a bee would respond to the scent subsequently. Bees that contacted the scented nectar 1–4 times during conditioning preferred the rewarded odour when tested 3 days later, but after 6 days their scent choice was random, suggesting they retained no memory of it. In contrast, bees that contacted the scented nectar 5–14 times chose the rewarded odour over an unrewarded odour 23 of 24 times when tested 6 days after exposure. This is the first confirmation of social learning in B. impatiens. Our results highlight the importance of direct contact with scented nectar in honeypots and the strong long-term memory of a rewarded scent acquired through relatively brief but repeated exposure to it. [ABSTRACT FROM AUTHOR]

Researchers of vertebrate navigation have investigated and debated intensely the existence of independent processes underlying spatial representation of environmental geometry and featural cues (e.g., landmarks). One of the most well-known behavioural instantiations of this dissociation originates from the differences in the way animals map locations in the surrounding environment with respect to the external cues such as boundaries or landmarks. Invertebrate researchers have joined this debate in the past few years, showing that insects can be trained to encode spatial locations using a variety of cues within small enclosures. In the present paper, we test insects in a non-rewarded, spontaneous navigation task. We observed bumblebees’ spatial navigation in response to the observed location of a conspecific, over manipulations of cue type and arena size. The results indicate that bumblebees spontaneously use both boundaries and features to guide their spatial behaviour. We discuss the similarities and differences in their behaviours to those of vertebrates and speculate on the implications of these findings. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine whether a preference by flower-naïve bumblebees could be created or enhanced by manipulating variables relevant to food collection and to defense against predation. In two experiments, colonies of bumblebees ( Bombus impatiens ) were deprived of pollen, exposed to CO 2 , or neither. Choices of individual workers in a radial arm maze were monitored. In Experiment 1, both variables lead to a preference for corridors occupied by a conspecific bee. The effect was specific: no change in preference for corridors occupied by other objects (a coin and a piece of Styrofoam) was detected. In Experiment 2, radial and concentric patterns were used, both of which were unoccupied. Only pollen deprivation increased preference for radial stimuli, while CO 2 had no discernible effect. Preferences for visual patterns by bees leaving their colony for the first time are modulated by variables that affect the internal state of the bees in problem-specific ways. [ABSTRACT FROM AUTHOR]

Stress has complex effects on learning and memory, depending on both the type of stress and when the animal experiences it. Honeybees and bumblebees are agriculturally important pollinators for whom the effects of stress are extremely relevant. These pollinators are often transported long distances during which colonies experience severe physical disturbance, causing stress to individuals prior to their release for pollination. Under natural foraging conditions, bees are excellent at learning about the flowers they forage from, including associations between floral stimuli and rewards. However, it is not clear how stress might affect bees’ abilities to learn and remember floral features. Here we address the effects of acute stress on learning and memory in the bumble bee, Bombus impatiens . Using the Proboscis Extension Response (PER) protocol, we look at stress effects on learning and memory in three experiments. After being trained to a conditioned stimulus, we addressed: (1) the effect of 24 h and (2) 30 min of stress on the recall of this learned association and (3) the effect of stress on subsequently learning an association. We found that 24 h of stress after learning appeared to improve memory recall, and there was a trend in the same direction for 30 min of stress. However, bees that were stressed prior to learning an association did not differ from unstressed bees in their ability to learn or remember an association. Our finding that stress has effects on memory in the bumblebee could have implications for their use in behavioral experiments and for promoting the success of both managed and wild populations. [ABSTRACT FROM AUTHOR]

To control flight, insects rely on the pattern of visual motion generated on the retina as they move through the environment. When light levels fall, vision becomes less reliable and flight control thus becomes more challenging. Here, we investigated the effect of light intensity on flight control by filming the trajectories of free-flying bumblebees (Bombus terrestris, Linnaeus 1758) in an experimental tunnel at different light levels. As light levels fell, flight speed decreased and the flight trajectories became more tortuous but the bees were still remarkably good at centring their flight about the tunnel's midline. To investigate whether this robust flight performance can be explained by visual adaptations in the bumblebee retina, we also examined the response speed of the green-sensitive photoreceptors at the same light intensities. We found that the response speed of the photoreceptors significantly decreased as light levels fell. This indicates that bumblebees have both behavioural (reduction in flight speed) and retinal (reduction in response speed of the photoreceptors) adaptations to allow them to fly in dim light. However, the more tortuous flight paths recorded in dim light suggest that these adaptations do not support flight with the same precision during the twilight hours of the day. [ABSTRACT FROM AUTHOR]

Here we describe for the first time the nesting behavior and the colony of Bombus ( Thoracobombus) brevivillus, a Neotropical species native only to South America. We discovered and observed seven B. brevivillus colonies between August and September 2012 in the state of Ceará, NE Brazil. Observations showed that B. brevivillus seems to be opportunistic in relation to nesting sites and brood protection, even though there is meager investment in nest building and offspring protection. Observations suggest that may be young B. brevivillus colonies invest strongly in brood production and colony development, before reproducing. More studies are necessary to evaluate the feasibility of captivity breeding of this species. [ABSTRACT FROM AUTHOR]

Bumblebees move about their environments by flying and by walking. Most experimental studies have addressed navigation during foraging flights, but we presented our experimental bees with the challenge of learning to navigate while walking as they must do in nature within topographically complex spaces containing their nests. We trained bumblebee workers to navigate complex, nine-channel, mazes in the absence of specific visual, chemical or textural cues. They successfully navigated through complex multi-turn mazes (stereotypical 'rat mazes') with several dead-ends by memorizing the entire sequence of appropriate turns, and their choice of correct first turn on entering the maze. Thus, their observed proficiencies indicated that the individual bumblebees had each memorized the maze by learning motor sequences which were not linked to visual, chemical or textural stimuli, and that their memories were triggered by contextual cues associated with the bees' positions in a sequence. Our findings have implications on natural ambulatory activities inside and outside the colony, and even in practical use as vectors of biological control agents. [ABSTRACT FROM AUTHOR]

The Tibetan plateau and its immediately surrounding mountains include the greatest hotspot of diversity worldwide for bumblebees, which are among the most important pollinators in temperate ecosystems. We make the first quantitative description of variation in the species composition of alpine social bumblebee faunas across the Tibetan plateau, for 44 species in 124 of the 307 one-degree grid cells. Data were compiled from field surveys, published sources and museum collections. Sampling effort could not be standardized across the region so our inferences have to be provisional. Faunal variation is described using detrended correspondence analysis (DCA); the faunal variation explained by climate variation is described using canonical correlation analysis (CCA); and the contribution of the climate data to the explanation is assessed using Procrustes analysis. Results show: (1) a particularly distinct group of endemic Himalayan faunas in the south; (2) a group of Tibetan interior faunas, with connections to faunas in the north-west in the Hindu Kush, Pamir and Tian Shan; and (3) a group of faunas in north-eastern Qinghai and Gansu, with connections to faunas to the north-east in Mongolia. The eastern and southern faunas in wetter habitats appear to be closer to equilibrium with climate factors, whereas some western faunas in more arid habitats appear further from equilibrium with the measured climate factors. One possibility is that these western faunas may depend on highly localized factors for mitigating the low precipitation over much of this region, and particularly on continuous summer streams with meltwater from distant permanent glaciers or high-ridge precipitation. Consequently, conservation threats to Tibetan bumblebees now include climate change causing loss of permanent streams in the west as well as the over-grazing documented in the east, threats that have not been major concerns for bumblebee conservation elsewhere. [ABSTRACT FROM AUTHOR]

The influence of space on the structure (e.g. modularity) of complex ecological networks remains largely unknown. Here, we sampled an individual-based plant-pollinator network by following the movements and flower visits of marked bumblebee individuals within a population of thistle plants for which the identities and spatial locations of stems were mapped in a 50 × 50 m study plot. The plant-pollinator network was dominated by parasitic male bumblebees and had a significantly modular structure, with four identified modules being clearly separated in space. This indicated that individual flower visitors opted for the fine-scale division of resources, even within a local site. However, spatial mapping of network modules and movements of bumblebee individuals also showed an overlap in the dense center of the plant patch. Model selection based on Akaike information criterion with traits as predictor variables revealed that thistle stems with high numbers of flower heads and many close neighbours were particularly important for connecting individuals within the modules. In contrast, tall plants and those near the patch center were crucial for connecting the different modules to each other. This demonstrated that individual-based plant-pollinator networks are influenced by both the spatial structure of plant populations and individual-specific plant traits. Additionally, bumblebee individuals with long observation times were important for both the connectivity between and within modules. The latter suggests that bumblebee individuals will still show locally restricted movements within sub-patches of plant populations even if they are observed over a prolonged time period. Our individual-based and animal-centered approach of sampling ecological networks opens up new avenues for incorporating foraging behaviour and intra-specific trait variation into analyses of plant-animal interactions across space. [ABSTRACT FROM AUTHOR]

Juvenile hormone (JH) is an important regulator of development and physiology in insects. While in many insect species, including bumble bees, JH functions as gonadotropin in adults, in some highly eusocial insects its role has shifted to regulate social behavior including division of labor, dominance and aggression. Studying JH functions across social insect species is important for understanding the evolution of sociality; however, these studies have been limited because of the inability to reduce JH levels without surgically removing its glandular source, the corpora allata. Precocene is known to inhibit JH biosynthesis in several non-social insects, but has been poorly studied in social insects. Here, we tested whether precocene- I can effectively reduce JH levels in Bombus terrestris workers, and examined its effects on their physiology and behavior. Precocene-I treatment of three-worker groups decreased JH titer and ovarian activation, irrespective of the bees' dominance rank within the group, and was remedied by JH replacement therapy. Precocene-I also decreased aggressiveness and increased ester-sterility signal production; these changes were rank-dependent, and affected mainly the most reproductive and the least aggressive workers, respectively, and could not be remedied by JH replacement therapy. These results clearly confirm the role of JH as a gonadotropin and mediator of aggression in B. terrestris, and indicate that JH effects are associated with worker dominance rank. The ability to chemically reduce JH titer provides us with a non-intrusive method to probe the evolutionary changes associated with JH and the hormonal mechanisms that are associated with reproduction and behavior in social insects. [ABSTRACT FROM AUTHOR]

Insects inform themselves about the 3D structure of their surroundings through motion parallax. During flight, they often simplify this task by minimising rotational image movement. Coordinated head and body movements generate rapid shifts of gaze separated by periods of almost zero rotational movement, during which the distance of objects from the insect can be estimated through pure translational optic flow. This saccadic strategy is less appropriate for assessing the distance between objects. Bees and wasps face this problem when learning the position of their nest-hole relative to objects close to it. They acquire the necessary information during specialised flights performed on leaving the nest. Here, we show that the bumblebee's saccadic strategy differs from other reported cases. In the fixations between saccades, a bumblebee's head continues to turn slowly, generating rotational flow. At specific points in learning flights these imperfect fixations generate a form of 'pivoting parallax', which is centred on the nest and enhances the visibility of features near the nest. Bumblebees may thus utilize an alternative form of motion parallax to that delivered by the standard 'saccade and fixate' strategy in which residual rotational flow plays a role in assessing the distances of objects from a focal point of interest. [ABSTRACT FROM AUTHOR]

In contrast to the wealth of knowledge concerning sucrose-rewarded learning, the question of whether bees learn when they collect pollen from flowers has been little addressed. The nutritional value of pollen varies considerably between species, and it may be that bees learn the features of flowers that produce pollen best suited to the dietary requirements of their larvae. It is still unknown, however, whether a non-ingestive reward pathway for pollen learning exists, and how foraging bees sense differences between pollen types. Here we adopt a novel experimental approach testing the learning ability of bees with pollen rewards. Bumblebees were reared under controlled laboratory conditions. To establish which pollen rewards are distinguishable, individual bees were given the choice of collecting two types of pollen, diluted to varying degrees with indigestible a- cellulose. Bees preferentially collected a particular pollen type, but this was not always the most concentrated sample. Preferences were influenced by the degree of similarity between samples and also by the period of exposure, with bees more readily collecting samples of lower pollen concentration after five trials. When trained differentially, bees were able to associate an initially less-preferred contextual colour with the more concentrated sample, whilst their pollen preferences did not change. Successful learning of contextual cues seems to maintain pollen foraging preferences over repeated exposures, suggesting that fast learning of floral cues may preclude continuous sampling and evaluation of alternative reward sources, leading to constancy in pollen foraging. [ABSTRACT FROM AUTHOR]

The Palaearctic Bombus ruderatus (in 1982/1983) and Bombus terrestris (1998) have both been introduced into South America ( Chile) for pollination purposes. We here report on the results of sampling campaigns in 2004, and 2010-2012 showing that both species have established and massively expanded their range., Bombus terrestris, in particular, has spread by some 200 km year−1 and had reached the Atlantic coast in Argentina by the end of 2011. Both species, and especially B. terrestris, are infected by protozoan parasites that seem to spread along with the imported hosts and spillover to native species., Genetic analyses by polymorphic microsatellite loci suggest that the host population of B. terrestris is genetically diverse, as expected from a large invading founder population, and structured through isolation by distance. Genetically, the populations of the trypanosomatid parasite, Crithidia bombi, sampled in 2004 are less diverse, and distinct from the ones sampled later. Current C. bombi populations are highly heterozygous and also structured through isolation by distance correlating with the genetic distances of B. terrestris, suggesting the latter's expansion to be a main structuring factor for the parasite., Remarkably, wherever B. terrestris spreads, the native Bombus dahlbomii disappears although the reasons remain unclear. Our ecological and genetic data suggest a major invasion event that is currently unfolding in southern South America with disastrous consequences for the native bumblebee species. [ABSTRACT FROM AUTHOR]

Whether invertebrates exhibit positive emotion–like states and what mechanisms underlie such states remain poorly understood. We demonstrate that bumblebees exhibit dopamine-dependent positive emotion–like states across behavioral contexts. After training with one rewarding and one unrewarding cue, bees that received pretest sucrose responded in a positive manner toward ambiguous cues. In a second experiment, pretest consumption of sucrose solution resulted in a shorter time to reinitiate foraging after a simulated predator attack. These behavioral changes were abolished with topical application of the dopamine antagonist fluphenazine. Further experiments established that pretest sucrose does not simply cause bees to become more exploratory. Our findings present a new opportunity for understanding the fundamental neural elements of emotions and may alter the view of how emotion states affect decision-making in animals. [ABSTRACT FROM AUTHOR]

The evolution of advanced sociality in bees is associated with apparent modifications in juvenile hormone (JH) signaling. By contrast to most insects in which JH is a gonadotropin regulating female fertility, in the highly eusocial honey bee (Apis mellifera) JH has lost its gonadotrophic function in adult females, and instead regulates age-related division of labor among worker bees. In order to shed light on the evolution of JH signaling in bees we performed allatectomy and replacement therapies to manipulate JH levels in workers of the "primitively eusocial" bumblebee Bombus terrestris. Allatectomized worker bees showed remarkable reduction in ovarian development, egg laying, Vitellogenin and Krüppel homolog 1 fat body transcript levels, hemolymph Vitellogenin protein abundance, wax secretion, and egg-cell construction. These effects were reverted, at least partially, by treating allatectomized bees with JH-III, the natural JH of bees. Allatectomy also affected the amount of ester component in Dufour's gland secretion, which is thought to convey a social signal relating to worker fertility. These findings provide a strong support for the hypothesis that in contrast to honey bees, JH is a gonadotropin in bumblebees and lend credence to the hypothesis that the evolution of advanced eusociality in honey bees was associated with major modifications in JH signaling. [ABSTRACT FROM AUTHOR]

Primates can analyse visual scenes extremely rapidly, making accurate decisions for presentation times of only 20 ms. We asked whether bumblebees, despite having potentially more limited processing power, could similarly detect and discriminate visual patterns presented for durations of 100 ms or less. Bumblebees detected stimuli and discriminated between differently oriented and coloured stimuli when presented as briefly as 25 ms but failed to identify ecologically relevant shapes (predatory spiders on flowers) even when presented for 100 ms. This suggests an important difference between primate and insect visual processing, so that while primates can capture entire visual scenes 'at a glance', insects might have to rely on continuous online sampling of the world around them, using a process of active vision, which requires longer integration times. [ABSTRACT FROM AUTHOR]

If the cognitive performance of animals reflects their particular ecological requirements, how can we explain appreciable variation in learning ability amongst closely related individuals (e.g. foraging workers within a bumble bee colony)? One possibility is that apparent 'errors' in a learning task actually represent an alternative foraging strategy. In this study we investigate the potential relationship between foraging 'errors' and foraging success among bumble bee ( Bombus terrestris) workers. Individual foragers were trained to choose yellow, rewarded flowers and ignore blue, unrewarded flowers. We recorded the number of errors (visits to unrewarded flowers) each bee made during training, then tested them to determine how quickly they discovered a more profitable food source (either familiar blue flowers, or novel green flowers). We found that error prone bees discovered the novel food source significantly faster than accurate bees. Furthermore, we demonstrate that the time taken to discover the novel, more profitable, food source is positively correlated with foraging success. These results suggest that foraging errors are part of an 'exploration' foraging strategy, which could be advantageous in changeable foraging environments. This could explain the observed variation in learning performance amongst foragers within social insect colonies. [ABSTRACT FROM AUTHOR]

Highlights: [•] An experimental approach to reproductive conflict in bumblebees. [•] Orphaned workers were paired according to levels of social activity. [•] Socially active pairs were more aggressive. [•] Aggression was not necessary for ovarian development. [•] Presence of brood depressed aggression and ovarian development. [ABSTRACT FROM AUTHOR]

Background: Bumblebees use information provided inadvertently by conspecifics when deciding between different flower foraging options. Such social learning might be explained by relatively simple associative learning mechanism: the bee may learn to associate conspecifics with nectar or pollen reward through previous experience of foraging jointly. However, in some studies, observers were guided by choices of ‘demonstrators’ viewed through a screen, so no reward was given to the observers at the time of seeing other bees’ flowers choice and no demonstrator bee was present at the moment of decision. This behaviour, referred to observational conditioning, implies an additional associative step as the positive value of conspecific is transferred to the associated flower. Here we explore the role of demonstrator movement, and the distance between observers and demonstrators that is required for observation conditioning to take place. Methodology/Principal Findings: We identify the conditions under which observational conditioning occurs in the widespread European species Bombus terrestris. The presence of artificial demonstrator bees leads to a significant change in individual colour preference toward the indicated colour if demonstrators were moving and observation distance was limited (15 cm), suggesting that observational conditioning could only influence relatively short-range foraging decisions. In addition, the movement of demonstrators is a crucial factor for observational conditioning, either due to the more life-like appearance of moving artificial bees or an enhanced detectability of moving demonstrators, and an increased efficiency at directing attention to the indicated flower colour. Conclusion: Bumblebees possess the capacity to learn the quality of a flower by distal observation of other foragers’ choices. This confirms that social learning in bees involves more advanced processes than simple associative learning, and indicates that observational conditioning might be widespread in pollinating insects, raising intriguing questions for the underlying mechanisms as well as the spread of social information in pollinator-plant interactions. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Effects of Aposematic Coloration on Predation Risk in Bumblebees? A Comparison between Differently Colored Populations, with Consideration of the Ultraviolet" by R.J. Stelzer and colleagues in a 2010 issue of the journal.

Ants on flowers can disrupt pollination by consuming rewards or harassing pollinators, but it is difficult to disentangle the effects of these exploitative and interference forms of competition on pollinator behavior. Using highly rewarding and quickly replenishing artificial flowers that simulate male or female function, we allowed bumblebees (Bombus impatiens) to forage (1) on flowers with or without ants (Myrmica rubra) and (2) on flowers with or without ant scent cues. Bumblebees transferred significantly more pollen analogue both to and from ant-free flowers, demonstrating that interference competition with ants is sufficient to modify pollinator foraging behavior. Bees also removed significantly less pollen analogue from ant-scented flowers than from controls, making this the first study to show that bees can use ant scent to avoid harassment at flowers. Ant effects on pollinator behavior, possibly in addition to their effects on pollen viability, may contribute to the evolution of floral traits minimizing ant visitation. [ABSTRACT FROM AUTHOR]

Abstract: The effects of floral herbivores on floral traits may result in alterations in pollinator foraging behaviour and subsequently influence plant reproductive success. Fed-upon plants may have evolved mechanisms to compensate for herbivore-related decreased fecundity. We conducted a series of field experiments to determine the relative contribution of floral herbivores and pollinators to female reproductive success in an alpine herb, Pedicularis gruina, in two natural populations over two consecutive years. Experimental manipulations included bagging, hand supplemental, geitonogamous pollination, and simulated floral herbivory. Bumblebees not only avoided damaged flowers and plants but also decreased successive visits of flowers in damaged plants, and the latter may reduce the level of geitonogamy. Although seed set per fruit within damaged plants was higher than that in intact plants, total seed number in damaged plants was less than that in intact plants, since floral herbivory-mediated pollinator limitation led to a sharp reduction of fruit set. Overall, the results suggest that resource reallocation within inflorescences of damaged plants may partially compensate for a reduction in seed production. Additionally, a novel finding was the decrease in successive within-plant bumblebee visits following floral herbivory. This may increase seed quantity and quality of P. gruina since self-compatible species exhibit inbreeding depression. The patterns of compensation of herbivory and its consequences reported in this study give an insight into the combined effects of interactions between floral herbivory and pollination on plant reproductive fitness. [Copyright &y& Elsevier]

Highlights: [•] Bombus terrestris foragers produce larger amounts of octyl esters compared to non-foragers. [•] Octyl esters are also known as a signal to sterility that reduces aggression. [•] Ester production is positively correlated with worker foraging efforts. [•] Foraging, potential fecundity and aggression are interlinked in B. terrestris workers. [Copyright &y& Elsevier]

Our understanding of how variable wind in natural environments affects flying insects is limited because most studies of insect flight are conducted in either smooth flow or still air conditions. Here, we investigate the effects of structured, unsteady flow (the von Karman vortex street behind a cylinder) on the flight performance of bumblebees (Bombus impatiens). Bumblebees are 'allweather' foragers and thus frequently experience variable aerial conditions, ranging from fully mixed, turbulent flow to unsteady, structured vortices near objects such as branches and stems. We examined how bumblebee flight performance differs in unsteady versus smooth flow, as well as how the orientation of unsteady flow structures affects their flight performance, by filming bumblebees flying in a wind tunnel under various flow conditions. The three-dimensional flight trajectories and orientations of bumblebees were quantified in each of three flow conditions: (1) smooth flow, (2) the unsteady wake of a vertical cylinder (inducing strong lateral disturbances) and (3) the unsteady wake of a horizontal cylinder (inducing strong vertical disturbances). In both unsteady conditions, bumblebees attenuated the disturbances induced by the wind quite effectively, but still experienced significant translational and rotational fluctuations as compared with flight in smooth flow. Bees appeared to be most sensitive to disturbance along the lateral axis, displaying large lateral accelerations, translations and rolling motions in response to both unsteady flow conditions, regardless of orientation. Bees also displayed the greatest agility around the roll axis, initiating voluntary casting maneuvers and correcting for lateral disturbances mainly through roll in all flow conditions. Both unsteady flow conditions reduced the upstream flight speed of bees, suggesting an increased cost of flight in unsteady flow, with potential implications for foraging patterns and colony energetics in natural, variable wind environments. [ABSTRACT FROM AUTHOR]

Visual search is well studied in human psychology, but we know comparatively little about similar capacities in non-human animals. It is sometimes assumed that animal visual search is restricted to a single target at a time. In bees, for example, this limitation has been evoked to explain flower constancy, the tendency of bees to specialise on a single flower type. Few studies, however, have investigated bee visual search for multiple target types after extended learning and controlling for prior visual experience. We trained colour-naive bumblebees (Bombus terrestris) extensively in separate discrimination tasks to recognise two rewarding colours in interspersed block training sessions. We then tested them with the two colours simultaneously in the presence of distracting colours to examine whether and how quickly they were able to switch between the target colours. We found that bees switched between visual targets quickly and often. The median time taken to switch between targets was shorter than known estimates of how long traces last in bees' working memory, suggesting that their capacity to recall more than one learned target was not restricted by working memory limitations. Following our results, we propose a model of memory and learning that integrates our findings with those of previous studies investigating flower constancy. [ABSTRACT FROM AUTHOR]

Understanding strategies used by animals to explore their landscape is essential to predict how they exploit patchy resources, and consequently how they are likely to respond to changes in resource distribution. Social bees provide a good model for this and, whilst there are published descriptions of their behaviour on initial learning flights close to the colony, it is still unclear how bees find floral resources over hundreds of metres and how these flights become directed foraging trips. We investigated the spatial ecology of exploration by radar tracking bumblebees, and comparing the flight trajectories of bees with differing experience. The bees left the colony within a day or two of eclosion and flew in complex loops of ever-increasing size around the colony, exhibiting Lévy-flight characteristics constituting an optimal searching strategy. This mathematical pattern can be used to predict how animals exploring individually might exploit a patchy landscape. The bees’ groundspeed, maximum displacement from the nest and total distance travelled on a trip increased significantly with experience. More experienced bees flew direct paths, predominantly flying upwind on their outward trips although forage was available in all directions. The flights differed from those of naïve honeybees: they occurred at an earlier age, showed more complex looping, and resulted in earlier returns of pollen to the colony. In summary bumblebees learn to find home and food rapidly, though phases of orientation, learning and searching were not easily separable, suggesting some multi-tasking. [ABSTRACT FROM AUTHOR]

Highlights: [•] Anthocyanins, dominated by delphanin, were more concentrated in purple- than in yellow-flowered Iris lutescens. [•] Purple and yellow flowers could be visually discriminated between by bumbleebees. [•] The overall chemical composition of scent was not significantly different between morphs. [•] The scent of both morphs was dominated by terpenoids. [•] Color-scent correlation was demonstrated based on their shared biosynthetic pathway. [Copyright &y& Elsevier]

It was found that the succinate oxidation rate in mitochondria of flight muscles of Bombus terrestris L. increased by a factor of 2.15 after flying for 1 h. An electrophoretically homogenous preparation of succinate dehydrogenase with a specific activity of 7.14 U/mg protein and 81.55-fold purity was isolated from B. terrestris flight muscles. It is shown that this enzyme is represented in the muscle tissue by only one isoform with R = 0.24. The molecular weight of the native molecule and its subunits A and B was determined. The kinetic characteristics of succinate dehydrogenase ( K = 0.33 mM) and the optimal concentration of hydrogen ions (pH 7.8) were established, and the effect of salts on the enzyme activity was studied. The role of succinate as a respiratory substrate in stress and the structural and functional characteristics of the succinate dehydrogenase system in the flight muscles of insects are discussed. [ABSTRACT FROM AUTHOR]

The results of behavioural experiments provide important information about the structure and information-processing abilities of the visual system. Nevertheless, if we want to infer from behavioural data how the visual system operates, it is important to know how different learning protocols affect performance and to devise protocols that minimise noise in the response of experimental subjects. The purpose of this work was to investigate how reinforcement schedule and individual variability affect the learning process in a colour discrimination task. Free-flying bumblebees were trained to discriminate between two perceptually similar colours. The target colour was associated with sucrose solution, and the distractor could be associated with water or quinine solution throughout the experiment, or with one substance during the first half of the experiment and the other during the second half. Both acquisition and final performance of the discrimination task (measured as proportion of correct choices) were determined by the choice of reinforcer during the first half of the experiment: regardless of whether bees were trained with water or quinine during the second half of the experiment, bees trained with quinine during the first half learned the task faster and performed better during the whole experiment. Our results confirm that the choice of stimuli used during training affects the rate at which colour discrimination tasks are acquired and show that early contact with a strongly aversive stimulus can be sufficient to maintain high levels of attention during several hours. On the other hand, bees which took more time to decide on which flower to alight were more likely to make correct choices than bees which made fast decisions. This result supports the existence of a trade-off between foraging speed and accuracy, and highlights the importance of measuring choice latencies during behavioural experiments focusing on cognitive abilities. [ABSTRACT FROM AUTHOR]

Bumblebees (Bombus terrestris) were trained to find one of the four exit holes located in the corners of an enclosed environment with a distinctive geometry (a rectangular cage). Panels located at the comers provided nongeometric, featural cues. Between trials bumblebees were passively disoriented to disable dead reckoning. When tested after removal of the panels, bumblebees reoriented using the residual information provided by the geometry of the cage. When tested after removal of only the two panels located in the two geometrically correct comers (the one with the exit and the diagonally opposite one), bumblebees were not able to use features in comers distant to the goal to reorient themselves. Finally, when geometric and featural cues provided contradictory information, bumblebees showed more reliance on featural cues. A similar outcome was observed when the conflict between geometrical and featural information was determined by first training bumblebees in a rectangular cage with a single wall of a different color used as a feature, and then testing animals with the feature displaced along a different wall. When the feature was close to the goal during training, bumblebees chose the corners with the feature at test, when the feature was far from goal during training, bumblebees chose the corners with the correct geometry at test. These results are similar to those revealed by similar transformational tests carried out in vertebrates relying mainly on vision for spatial orientation, that is, birds and monkeys. [ABSTRACT FROM AUTHOR]

Despite the ubiquity and the importance of interspecific interactions among flower visitors, few studies have examined their effects on the realized feeding niches of visitor species in a community context. To evaluate the community-wide effects of interactions among flower visitors, I have examined changes in the flower utilization patterns of each visitor species at several sites where the component of the visitor's community differed. Specifically, I compared the flower preferences and foraging habits (legitimate foraging vs. primary nectar robbing vs. secondary nectar robbing) of five bumble bee species in flower patches consisting of Trifolium pratense L. (red clover) and T. repens L. (white clover) on Hokkaido Island, Japan. I also examined the nectar production and standing crops of each flower species to evaluate the exploitation competition based on nectar. The bumble bee species exhibited different flower utilization patterns among sites. At sites where the long-tongued Bombus diversus tersatus was common and the exotic short-tongued B. terrestris was rare, B. diversus tersatus visited red clover (long-tubed flowers) exclusively, whereas medium-tongued B. pseudobaicalensis and short-tongued B. hypocrita sapporoensis and B. hypnorum koropokkrus preferentially visited white clover (short-tubed flowers). Conversely, at sites where the long-tongued bee was rare, four other species frequently visited red clover in different modes: B. pseudobaicalensis visited legitimately, B. hypocrita sapporoensis and B. terrestris visited as primary nectar robbers, and B. hypnorum koropokkrus visited as a secondary nectar robber. The presence or absence of resource exploitation by the long-tongued species and the interaction between primary and secondary nectar robbers via robbing holes was the major ecological sources of these differences. Diverse effects of interactions among flower visitors played important roles in shaping pattern of plant and flower visitor interactions. [ABSTRACT FROM AUTHOR]

The capacity to discriminate between choice options is crucial for a decision-maker to avoid unprofitable options. The physical properties of rewards are presumed to be represented on context-dependent, nonlinear cognitive scales that may systematically influence reward expectation and thus choice behavior. In this study, we investigated the discrimination performance of free-flying bumblebee workers ( Bombus impatiens) in a choice between sucrose solutions with different concentrations. We conducted two-alternative free choice experiments on two B. impatiens colonies containing some electronically tagged bumblebees foraging at an array of computer-automated artificial flowers that recorded individual choices. We mimicked natural foraging conditions by allowing uncertainty in the probability of reward delivery while maintaining certainty in reward concentration. We used a Bayesian approach to fit psychometric functions, relating the strength of preference for the higher concentration option to the relative intensity of the presented stimuli. Psychometric analysis was performed on visitation data from individually marked bumblebees and pooled data from unmarked individuals. Bumblebees preferred the more concentrated sugar solutions at high stimulus intensities and showed no preference at low stimulus intensities. The obtained psychometric function is consistent with reward evaluation based on perceived concentration contrast between choices. We found no evidence that bumblebees reduce reward expectations upon experiencing non-rewarded visits. We compare psychometric function parameters between the bumblebee B. impatiens and the flower bat Glossophaga commissarisi and discuss the relevance of psychophysics for pollinator-exerted selection pressures on plants. [ABSTRACT FROM AUTHOR]

Animals collecting food from renewable resource patches scattered in space often establish small foraging areas to which they return faithfully. Such area fidelity offers foraging advantages through selection of profitable patches, route minimization, and regular circuit visits to these patches (“trapline foraging”). Resource distribution under field conditions may often vary in time, however, especially when competitors suddenly vanish and a number of patches become available for their neighbors. Previous studies suggested that site-faithful foragers of bumble bees quickly respond to such unexpected events by readjusting their foraging areas, although it is not clear how much their foraging performance was improved, beyond the simple relaxation of competitive pressure, or how they manifest such flexibility while persistently using certain foraging areas or paths. Here, we conducted indoor flight-cage experiments with bumble bees and found that a bee, when encountering a loss of its competitor, improved its foraging performance to a greater extent than expected from a simple relaxation of competitive pressure by increasing the size of its foraging area. Moreover, bees with better-established traplines achieved greater foraging areas after the loss of competitors, suggesting that bees do not necessarily need to “sample” neighboring patches to monitor temporal changes in environments. We discuss how periodical returns and route memory associated with accurate reward values could allow inherently conservative trapliners to make flexible adjustments, by effectively monitoring their circumstances and quickly readjusting to detected changes. [ABSTRACT FROM AUTHOR]

Pollinators such as bees are essential to the functioning of terrestrial ecosystems. However, despite concerns about a global pollinator crisis, long-term data on the status of bee species are limited. We present a long-term study of relative rates of change for an entire regional bee fauna in the northeastern United States, based on >30,000 museum records representing 438 species. Over a 140-y period, aggregate native species richness weakly decreased, but richness declines were significant only for the genus Bombus. Of 187 native species analyzed individually, only three declined steeply, all of these in the genus Bombus. However, there were large shifts in community composition, as indicated by 56% of species showing significant changes in relative abundance over time. Traits associated with a declining relative abundance include small dietary and phenological breadth and large body size. In addition, species with lower latitudinal range boundaries are increasing in relative abundance, a finding that may represent a response to climate change. We show that despite marked increases in human population density and large changes in anthropogenic land use, aggregate native species richness declines were modest outside of the genus Bombus. At the same time, we find that certain ecological traits are associated with declines in relative abundance. These results should help target conservation efforts focused on maintaining native bee abundance and diversity and therefore the important ecosystems services that they provide. [ABSTRACT FROM AUTHOR]

Bumblebees tend to face their nest over a limited range of compass directions when learning the nest's location on departure and finding it on their approach after foraging. They thus obtain similar views of the nest and its surroundings on their learning and return flights. How do bees coordinate their flights relative to nest-based and compass-based reference frames to get such similar views? We show, first, that learning and return flights contain straight segments that are directed along particular compass bearings, which are independent of the orientation of a bee's body. Bees are thus free within limits to adjust their viewing direction relative to the nest, without disturbing flight direction. Second, we examine the coordination of nest-based and compass-based control during likely information gathering segments of these flights: loops during learning flights and zigzags on return flights. We find that bees tend to start a loop or zigzag when flying within a restricted range of compass directions and to fly towards the nest and face it after a fixed change in compass direction, without continuous interactions between their nest-based and compass-based directions of flight. A preferred trajectory of compass-based flight over the course of a motif, combined with the tendency of the bees to keep their body oriented towards the nest automatically narrows the range of compass directions over which bees view the nest. Additionally, the absence of interactions between the two reference frames allows loops and zigzags to have a stereotyped form that can generate informative visual feedback. [ABSTRACT FROM AUTHOR]

Many wasps and bees learn the position of their nest relative to nearby visual features during elaborate 'learning' flights that they perform on leaving the nest. Return flights to the nest are thought to be patterned so that insects can reach their nest by matching their current view to views of their surroundings stored during learning flights. To understand how ground-nesting bumblebees might implement such a matching process, we have video-recorded the bees' learning and return flights and analysed the similarities and differences between the principal motifs of their flights. Loops that take bees away from and bring them back towards the nest are common during learning flights and less so in return flights. Zigzags are more prominent on return flights. Both motifs tend to be nest based. Bees often both fly towards and face the nest in the middle of loops and at the turns of zigzags. Before and after flight direction and body orientation are aligned, the two diverge from each other so that the nest is held within the bees' fronto-lateral visual field while flight direction relative to the nest can fluctuate more widely. These and other parallels between loops and zigzags suggest that they are stable variations of an underlying pattern, which enable bees to store and reacquire similar nest-focused views during learning and return flights. [ABSTRACT FROM AUTHOR]

Despite the expansion of phylogenetic community analysis to understand community assembly, few studies have used these methods on mobile organisms and it has been suggested the local scales that are typically considered may be too small to represent the community as perceived by organisms with high mobility. Mobility is believed to allow species to mediate competitive interactions quickly and thus highly mobile species may appear randomly assembled in local communities. At larger scales, however, biogeographical processes could cause communities to be either phylogenetically clustered or even. Using phylogenetic community analysis we examined patterns of relatedness and trait similarity in communities of bumble bees (Bombus) across spatial scales comparing: local communities to regional pools, regional communities to continental pools and the continental community to a global species pool. Species composition and data on tongue lengths, a key foraging trait, were used to test patterns of relatedness and trait similarity across scales. Although expected to exhibit limiting similarity, local communities were clustered both phenotypically and phylogenetically. Larger spatial scales were also found to have more phylogenetic clustering but less trait clustering. While patterns of relatedness in mobile species have previously been suggested to exhibit less structure in local communities and to be less clustered than immobile species, we suggest that mobility may actually allow communities to have more similar species that can simply limit direct competition through mobility. [ABSTRACT FROM AUTHOR]

The movement of organisms is subject to a multitude of influences of widely varying character: from the bio-mechanics of the individual, over the interaction with the complex environment many animals live in, to evolutionary pressure and energy constraints. As the number of factors is large, it is very hard to build comprehensive movement models. Even when movement patterns in simple environments are analysed, the organisms can display very complex behaviours. While for largely undirected motion or long observation times the dynamics can sometimes be described by isotropic random walks, usually the directional persistence due to a preference to move forward has to be accounted for, e.g., by a correlated random walk. In this paper we generalise these descriptions to a model in terms of stochastic differential equations of Langevin type, which we use to analyse experimental search flight data of foraging bumblebees. Using parameter estimates we discuss the differences and similarities to correlated random walks. From simulations we generate artificial bumblebee trajectories which we use as a validation by comparing the generated ones to the experimental data. [ABSTRACT FROM AUTHOR]

Flexible division of labour is a key feature of social insects. Our understanding of individual response behaviour and how it is integrated into a functioning colony is still patchy. Most theoretical studies addressing this question are based on the assumption that workers have intrinsic and often fixed response thresholds for task-related stimuli. Here, we investigated the plasticity in worker fanning response behaviour in a bumblebee, Bombus terrestris. Using a temperature-controlled brood dummy, we first asked whether the fanning response is modulated by rate of temperature change. Second, we examined to what extent the fanning response is influenced by recent fanning experience. Our results show that the individual fanning response is modulated by both the rate of temperature increase and recent experience. Workers responded at lower temperatures and with a higher probability when the temperature of the brood dummy increased slowly compared with more rapid temperature increases. Workers that repeatedly responded to an increase in brood dummy temperature with fanning showed a significant decrease in their response thresholds, whereas the response thresholds of control workers that experienced the same treatment but did not gather fanning experience remained unchanged. The decrease in response threshold was pronounced when the time interval between two successive fanning events was less than 6h. When 16h or more separated fanning events, individual fanning responses returned to higher threshold levels. We suggest that experience-dependent modulation of response thresholds plays an important role in the behavioural differentiation of workers and the flexibility of insect colonies. [Copyright &y& Elsevier]

One of the concerns surrounding the commercial release of genetically modified ( GM) crops is the escape of transgenes into agricultural or semi-natural habitats through vertical gene flow, as this may cause environmental or economic problems. There is also the concern that GM crops may affect pollinators and the pollination services they provide. Despite the growing commercial interest of GM tomato ( Solanum lycopersicum), gene flow has been assessed only sparsely in tomato. To evaluate the likelihood of gene flow from GM tomato plants to sexually compatible plants, and to assess whether bumblebee activity is affected by GM tomato, three experiments were conducted under greenhouse conditions, using a Bt-tomato expressing the insecticidal Cry3Bb1 protein as model system: (a) artificial crosses between a GM tomato line, two wild tomato relatives ( Solanum hirsutum and Solanum nigrum) and a non- GM tomato variety; (b) bumblebee-mediated crosses between GM and non- GM tomato plants and (c) visual observations of bumblebees' feeding behaviour. No hybrids were obtained between the GM tomato line and S. hirsutum and S. nigrum. In an experimental design where non- GM receptor plants outnumbered GM plants by approximately 3:1, the bumblebee-mediated cross-fertilisation rate between GM and non- GM tomato plants was measured at 4.3 ± 5.47%. No significant differences in feeding behaviour of bumblebees foraging on GM and non- GM tomato plants were observed. Therefore, we conclude that: (a) the probability of transgene introgression between the GM tomato line used in this study and its wild relatives S. hirsutum and S. nigrum is negligible; (b) bumblebee activity can mediate cross-fertilisation between GM and non- GM tomato and (3) the Cry3Bb1-expressing tomato line tested does not adversely affect the feeding behaviour of bumblebees. [ABSTRACT FROM AUTHOR]

Mechanisms of spatial attention are used when the amount of gathered information exceeds processing capacity. Such mechanisms have been proposed in bees, but have not yet been experimentally demonstrated. We provide evidence that selective attention influences the foraging performance of two social bee species, the honeybee Apis mellifera and the bumblebee Bombus terrestris. Visual search tasks, originally developed for application in human psychology, were adapted for behavioural experiments on bees. We examined the impact of distracting visual information on search performance, which we measured as error rate and decision time. We found that bumblebees were significantly less affected by distracting objects than honeybees. Based on the results, we conclude that the search mechanism in honeybees is serial like, whereas in bumblebees it shows the characteristics of a restricted parallel-like search. Furthermore, the bees differed in their strategy to solve the speed-accuracy trade-off. Whereas bumblebees displayed slow but correct decision-making, honeybees exhibited fast and inaccurate decision-making. We propose two neuronal mechanisms of visual information processing that account for the different responses between honeybees and bumblebees, and we correlate species-specific features of the search behaviour to differences in habitat and life history. [ABSTRACT FROM AUTHOR]

Abstract: Spring queens of Bombus cryptarum from Europe, Bombus burjaeticus from the Russian Transbaikal region and Bombus moderatus from North America were collected at different localities to grow artificial colonies and obtain fresh males. Furthermore, males of Bombus florilegus, B. moderatus, Bombus magnus and Bombus occidentalis were collected in the field. Cephalic labial gland secretions of 29 specimens from these different taxa were analysed by gas chromatography/mass spectrometry (GC/MS). About 50 compounds were identified, including a mixture of straight-chain fatty acid derivatives (alkenoles, acids, acetates and esters), and the usual pattern of saturated and unsaturated hydrocarbons C21–C29. The secretions of all specimens investigated were very similar: ethyl dodecanoate was identified as the main component (90–97% peak area). Since the sum of percentage peak areas for the hydrocarbons amounted up to 3–6%, most of the remaining compounds (8 alkenoles, 6 acids, 6 acetates and 20 esters) could only be detected at very low levels (<0.1% peak area). With the exception of B. florilegus, each taxon had a sympatric bumblebee taxon that also used ethyl dodecanoate as the main component: B. magnus, sympatric with B. cryptarum in Europe, Bombus patagiatus, sympatric with B. burjaeticus in the Russian Transbaikal and B. occidentalis, sympatric with B. moderatus in North America. Male cephalic labial gland secretions of 20 specimens from these sympatric taxa were also investigated to see how far their pattern of compounds differed from that of the cryptarum complex taxa (cryptarum–burjaeticus–florilegus–moderatus). Besides some quantitative differences in ethyl dodecanoate and ethyl octadec-9-enoate, the occurrence of octadeca-9,12-dien-1-ol, octadeca-9,12,15-trien-1-ol and octadec-11-en-1-ol was an essential qualitative difference that separated the labial gland secretions of B. magnus, B. patagiatus and B. occidentalis from those of their sympatric counterparts. A principal component analysis confirmed this separation. Due to their low variability and differences in pattern of compounds compared to those of closely related sympatric bumblebees, the labial gland secretions of B. cryptarum, B. burjaeticus, B. florilegus and B. moderatus distributed across Europe, the Russian Far East and North America are very well suited to function as ‘species recognition signal’. The taxonomic consequences for the cryptarum complex taxa and their relationship to Bombus albocinctus from the Russian Far East are discussed in context of recent genetic investigations. [Copyright &y& Elsevier]

Bumblebees ( Bombus spp.) foraging in the field typically reject flowers where they detect the olfactory footprints of previous visitors and hence avoid recently emptied inflorescences. A growing number of studies have begun to illustrate that associative learning shapes the development of this process, in both bumblebees and other bee species. This raises the question of what the default response to such marks is, but little is known about how inexperienced foragers use social information. Here, we offered flower-naive bees a choice between scent-marked flowers and unmarked alternatives and found that individuals neither avoided nor preferred marked flowers. Our findings provide no support for 'hard-wired' responses to scent marks in bumblebees and highlight the importance of associative learning in shaping social information use to match local circumstances. [ABSTRACT FROM AUTHOR]

Although the practice of cultivating mass flowering crops (MFCs) is seen as a means of counteracting the widespread decline of insect pollinators, no study to-date has evaluated whether the increased pollinator abundance associated with MFCs influences pollinator visits to assemblages of adjacent native, non-crop plant species (pollinator 'spill-over'). In this study we quantified bumblebee abundance along hedgerow transects in MFC (field bean) vs non-MFC (wheat) margins. Surveys were conducted on east and west-facing margins twice daily (morning and afternoon) for three or four days during the main MFC flowering period (June) over four years involving paired bean and wheat fields in Devon and Cornwall, southwest England. Although no single bumblebee species showed any consistent change in relative frequency, when taken across all years and bumblebee species combined, we observed twice as many bumblebees visiting flowers adjacent to the MFC. However, when we compared bumblebee activity along hedgerow transects two weeks after bean flowering, there was no difference between crops. We thus conclude that although there is evidence for pollinator spill-over from the bean MFC to nearby semi-natural habitat, the effect is comparatively short lived and not specific to any single bumblebee species. We also suggest that while pollinator services to native plant species might be briefly enhanced by MFC cultivation, the possible repercussions of bumblebee spill-over from MFCs to semi-natural habitats and the other pollinator groups they support should be evaluated before MFC cultivation is considered as a means of conserving declining bumblebee populations. [ABSTRACT FROM AUTHOR]

Conspecifics are usually considered competitors negatively affecting food intake rates. However, their presence can also inform about resource quality by providing inadvertent social information. Few studies have investigated whether foragers perceive conspecifics as informers or competitors. Here, we experimentally tested whether variation in the density of demonstrators ('none', 'low' and 'high'), whose location indicated flower profitability, affected decision-making of bumble-bees Bombus terrestris. Bumble-bees foraged on either 'simple' (two colours) or 'complex' (four colours) artificial floral communities. We found that conspecifics at low density may be used as sources of information in first flower choices, whereas they appeared as competitors over the whole foraging sequence. Low conspecific densities improved foragers' first-visit success rate in the simple environment, and decreased time to first landing, especially in the complex environment. High conspecific densities did not affect these behavioural parameters, but reduced flower constancy in both floral communities, which may alter the efficiency of pollinating visits. These results suggest that the balance of the costs and benefits of conspecific presence varies with foraging experience, floral community and density. Spatio-temporal scales could thus be an important determinant of social information use. This behavioural flexibility should allow bumble-bees to better exploit their environment. [ABSTRACT FROM AUTHOR]

Many antagonistic species attack plants and consume specific plant parts. Understanding how these antagonists affect plant fitness individually and in combination is an important research focus in ecology and evolution. We examined the individual and combined effects of herbivory, nectar robbing, and pre-dispersal seed predation on male and female estimates of fitness in the host plant Ipomopsis aggregata. By examining the effects of antagonists on plant traits, we were able to tease apart the direct consumptive effects of antagonists versus the indirect effects mediated through changes in traits important to pollination. In a three-way factorial field experiment, we manipulated herbivory, nectar robbing, and seed predation. Herbivory and seed predation reduced some male and female fitness estimates, whereas plants tolerated the effects of robbing. The effects of herbivory, robbing, and seed predation were primarily additive, and we found little evidence for non-additive effects of multiple antagonists on plant reproduction. Herbivory affected plant reproduction through both direct consumptive effects and indirectly through changes in traits important to pollination (i.e., nectar and phenological traits). Conversely, seed predators primarily had direct consumptive effects on plants. Our results suggest that the effects of multiple antagonists on estimates of plant fitness can be additive, and investigating which traits respond to damage can provide insight into how antagonists shape plant performance. [ABSTRACT FROM AUTHOR]

Background: Accurate estimates of movement behavior and distances travelled by animals are difficult to obtain, especially for small-bodied insects where transmitter weights have prevented the use of radio-tracking. Methodology/Principal Findings: Here, we report the first successful use of micro radio telemetry to track flight distances and space use of bumblebees. Using ground surveys and Cessna overflights in a Central European rural landscape mosaic we obtained maximum flight distances of 2.5 km, 1.9 km and 1.3 km for Bombus terrestris (workers), Bombus ruderatus (worker), and Bombus hortorum (young queens), respectively. Bumblebee individuals used large areas (0.25-43.53 ha) within one or a few days. Habitat analyses of one B. hortorum queen at the landscape scale indicated that gardens within villages were used more often than expected from habitat availability. Detailed movement trajectories of this individual revealed that prominent landscape structures (e.g. trees) and flower patches were repeatedly visited. However, we also observed long (i.e. .45 min) resting periods between flights (B. hortorum) and differences in flower-handling between bumblebees with and without transmitters (B. terrestris) suggesting that the current weight of transmitters (200 mg) may still impose significant energetic costs on the insects. Conclusions/Significance: Spatio-temporal movements of bumblebees can now be tracked with telemetry methods. Our measured flight distances exceed many previous estimates of bumblebee foraging ranges and suggest that travelling long distances to food resources may be common. However, even the smallest currently available transmitters still appear to compromise flower handling performance and cause an increase in resting behavior of bees. Future reductions of transmitter mass and size could open up new avenues for quantifying landscape-scale space use of insect pollinators and could provide novel insights into the behavior and requirements of bumblebees during critical life stages, e.g. when searching for mates, nest locations or hibernation sites. [ABSTRACT FROM AUTHOR]