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Burmannia shows a set of floral traits that suggest elaborate mechanisms of animal mediated pollen transfer. These include flower coloration, septal nectaries and a long and narrow floral chamber. The stamens are synorganized with the common style restricting the entrance to the floral chamber, sometimes forming a gynostegium. Contrary to this apparent zoophilous floral syndrome, several species of Burmannia were reported to perform self-pollination via cleistogamy. Understanding of reproductive systems in Burmannia is complicated by scarcity of available results of direct observations on pollination process. Here we present data on pollination biology of B. disticha obtained during field investigations in Vietnam followed by laboratory analyses of ecologically important floral traits and the captured flower visitors. We found that the anthetic perianth is open, i.e. the flower is chasmogamous. The flowers are visited by various Diptera, Hymenoptera, Lepidoptera and Orthoptera. Of them, the bumblebees (Bombus burmensis), a bee (Coelioxys sp.) and some lepidopterans were revealed to carry pollen of B. disticha. Based on the amount of carried pollen, insect behavior during the visits and general knowledge on biology of these insect taxa, we concluded that the bumblebees act as the principal pollinators of B. disticha, whereas the lepidopterans are considered as its possible pollinators. We compared the lengths of proboscises of the captured insects to the depth of the floral chamber, and found that only the bumblebees and lepidopterans should be able to reach the nectar. Finally, we estimated the pollen-ovule ratio of B. disticha as 6.84, which is comparable to the ratio known in autogamous angiosperms. Based on its flower organization and pollination mechanism, we consider B. disticha an entomophilous and predominantly xenogamous species. Its gynostegium is likely an adaptation for pollen transfer by insects with long proboscises. At the same time, earlier investigations together with pollen-ovule ratio indicate that B. disticha possesses a labile pollination strategy, and autogamy sometimes occurs. Since Burmannia is one of the few angiosperm genera that comprise both mycoheterotrophic (achlorophyllous) and autotrophic (green) species, our study provides important evidence for reconstructions of ecological and morphological evolutionary pathways in relation to the mode of organic nutrition. [ABSTRACT FROM AUTHOR]

A key question in pollination biology is that of how pollinators identify and choose foraging patches. Several approaches have been employed for this, including field studies and large greenhouse flight chambers. Most methods used to date are limited, though, by reliance on a combination of artificial flowers, large spatial scales, or lack of spatially distinct floral patches. To address this issue, we designed and tested a y-maze flight arena and tested it using the bumblebee Bombus impatiens and canola plants. Our results indicate that the system is not biased by environmental conditions, or by an innate "handedness" of Bombus impatiens. We found that bees made all the expected patch choices when presented with soil, plants without flowers, or plants with flowers. This new method is important and useful as it allows researchers to ask questions of both plant health and insect behavior and the chamber system is modular allowing for simple changes to the setup to focus on different questions. Highlights: • Y-maze flight arena was designed to evaluate foraging behavior on intact plants. • No evidence of side preference in individual bees. • Behaviors observed in the y-maze appear to correspond to behaviors observed in other settings. [ABSTRACT FROM AUTHOR]

A recent study published in Current Biology reveals that bumble bees bite down on flowers to enhance their ability to vibrate and shake out pollen. This behavior, known as "buzz pollination," is used by about 9% of plants, including important crops like potatoes, tomatoes, and peas. The study found that when bees bit the anthers of buzz-pollinated flowers, they transmitted up to three times more vibration, resulting in more pollen collection. However, the reasons behind why bees bite and the mechanics of their head shakes remain unknown. This research highlights the complexity of insect behavior and the need for further investigation. [Extracted from the article]

Flowers act as multisensory billboards to pollinators by using a range of sensory modalities such as visual patterns and scents. Different floral organs release differing compositions and quantities of the volatiles contributing to floral scent, suggesting that scent may be patterned within flowers. Early experiments suggested that pollinators can distinguish between the scents of differing floral regions, but little is known about how these potential scent patterns might influence pollinators.We show that bumblebees can learn different spatial patterns of the same scent, and that they are better at learning to distinguish between flowers when the scent pattern corresponds to a matching visual pattern. Surprisingly, once bees have learnt the spatial arrangement of a scent pattern, they subsequently prefer to visit novel unscented flowers that have an identical arrangement of visual marks, suggesting that multimodal floral signals may exploit the mechanisms by which learnt information is stored by the bee. [ABSTRACT FROM AUTHOR]

This study examines the mechanism underlying one way in which bumblebees are known to develop a preference for symmetric patterns: through prior non-differential reinforcement on simple patterns (black discs and white discs). In three experiments, bees were given a choice among symmetric and asymmetric black-and-white non-rewarding patterns presented at the ends of corridors in a radial maze. Experimental groups had prior rewarded non-discrimination training on white patterns and black patterns, while control groups had no pre-test experience outside the colony. No preference for symmetry was obtained for any of the control groups. Prior training with circular patterns highlighting a horizontal axis of symmetry led to a specific subsequent preference for horizontal over vertical symmetry, while training with a vertical axis abolished this effect. Circles highlighting both axes created a general avoidance of asymmetry in favour of symmetric patterns with vertical, horizontal or both axes of symmetry. Training with plain circles, but not with deformed circles, led to a preference for symmetry: there was no evidence that the preference emerged just by virtue of having attention drawn away from irrelevant pattern differences. Our results point to a preference for symmetry developing gradually through first learning to extract an axis of symmetry from simple patterns and subsequently recognizing that axis in new patterns. They highlight the importance of continued learning through non-differential reinforcement by skilled foragers. Floral guides can function not only to guide pollinators to the source of reward but also to highlight an axis of symmetry for use in subsequent floral encounters. [ABSTRACT FROM AUTHOR]

Invasive species are considered a main driver of pollinator declines, yet the direct effects of invasive alien plants on pollinators are poorly understood., Abundant, invasive plant species can provide a copious nectar resource for native pollinators. However, the nectar of some plants contains secondary compounds, usually associated with defence against herbivores. The impacts of these compounds on pollinators are often unknown., We compared how consumption of grayanotoxin I and III, natural secondary compounds in the nectar of invasive Rhododendron ponticum L., affected three native bee species: a honeybee, ( Apis mellifera L.), a solitary mining bee ( Andrena carantonica, Pérez) and a bumblebee, ( Bombus terrestris, L.)., Survival of the solitary bee and the bumblebee species was not affected by either grayanotoxin, but honeybees were ∼20× more likely to die when fed solutions containing grayanotoxin I. Furthermore, solitary bees were deterred from feeding and exhibited malaise behaviours indicative of sublethal toxicity in response to consumption of grayanotoxin I. In contrast, grayanotoxins did not affect bumblebee survival or behaviour, even when bees were subjected to multiple stressors (parasite infection or food stress)., Our experiments suggest that while R. ponticum provides abundant floral nectar, it is only available as a food resource to pollinators that tolerate grayanotoxins. Pollinators whose health is negatively affected by grayanotoxins may experience negative impacts from R. ponticum invasion directly (if they consume R. ponticum nectar) or indirectly (if native floral resources are replaced by R. ponticum)., Our study makes a novel comparison of the effects of a natural nectar secondary compound on three pollinator species and clearly demonstrates drastic variation in the responses of different key pollinator taxa to a nectar toxin. Our findings are thus in congruence with literature demonstrating the varying effects of invasive plant chemistry on native foliar herbivores, and our work demonstrates that nectar chemistry should be taken into account when determining the impacts of plant invasion for native pollinators. [ABSTRACT FROM AUTHOR]

Untrained, “flower-naïve” bumblebees display behavioural preferences when presented with visual properties such as colour, symmetry, spatial frequency and others. Two unsupervised neural networks were implemented to understand the extent to which these models capture elements of bumblebees’ unlearned visual preferences towards flower-like visual properties. The computational models, which are variants of Independent Component Analysis and Feature-Extracting Bidirectional Associative Memory, use images of test-patterns that are identical to ones used in behavioural studies. Each model works by decomposing images of floral patterns into meaningful underlying factors. We reconstruct the original floral image using the components and compare the quality of the reconstructed image to the original image. Independent Component Analysis matches behavioural results substantially better across several visual properties. These results are interpreted to support a hypothesis that the temporal and energetic costs of information processing by pollinators served as a selective pressure on floral displays: flowers adapted to pollinators’ cognitive constraints. [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]

The presence of yeasts in pollen and floral nectar is rather the norm than the exception. Due to the metabolic activities of yeasts, sugar and amino acid composition of nectar often drastically change and may negatively impact the nutritional value of nectar for pollinators and hence insect fitness. On the other hand, the presence of yeasts in floral nectar may also increase its nutritional value due to yeast's probiotic effect and the release of yeast's metabolites. In this study, we investigated whether the presence of defined flower‐ and insect‐associated yeasts affected individual and colony fitness of the bumble bee pollinator Bombus terrestris. Specifically, we tested whether the presence of yeasts in nectar affected bumble bee foraging behavior and nectar consumption, individual growth and colony development, larval and queen mortality, and mating success. Quantitative analyses of sugar and amino acid profiles showed that nectar yeasts significantly affected the chemical composition of nectar. However, dual‐choice experiments indicated that yeast inoculation did not significantly affect foraging behavior or consumption rates. Nest development, on the other hand, was significantly affected by the presence of yeasts, but effects largely depended on species identity, with Candida bombiphila, Metschnikowia gruessii, and Rhodotorula mucilaginosa having the largest positive impact on colony growth. Interestingly, the effects at the colony level were more pronounced than at the individual level. In vitro growth tests further showed that yeasts have the potential to suppress the growth of the bumble bee gut pathogen Crithidia bombi. Overall, these results demonstrate that nectar‐inhabiting yeasts can have diverse effects on bumble bee fitness and therefore may mediate plant–pollinator mutualisms. [ABSTRACT FROM AUTHOR]