Illumination preference, illumination constancy and colour discrimination by bumblebees in an environment with patchy light

Arnold, Sarah E. J.; Chittka, Lars

doi:10.1242/jeb.065565

Cited by 27 publications

(26 citation statements)

References 25 publications

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“…Since different types of illumination can affect bee vision (Arnold and Chittka, 2012) conducting experiments across a variety of lighting regimes may be important. However, brightness has generally been found to be an unimportant variable when chromatic differences provide for discrimination.…”

Section: Discussionmentioning

confidence: 99%

Wild bees preferentially visitRudbeckiaflower heads with exaggerated ultraviolet absorbing floral guides

2014

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Here, we report on the results of an experimental study that assessed the visitation frequency of wild bees to conspecific flowers with different sized floral guides. UV absorbent floral guides are ubiquitous in Angiosperms, yet surprisingly little is known about conspecific variation in these guides and very few studies have evaluated pollinator response to UV guide manipulation. This is true despite our rich understanding about learning and color preferences in bees. Historical dogma indicates that flower color serves as an important long-range visual signal allowing pollinators to detect the flowers, while floral guides function as close-range signals that direct pollinators to a reward. We initiated the work presented here by first assessing the population level variation in UV absorbent floral guides for conspecific flowers. We assessed two species, Rudbeckia hirta and R. fulgida. We then used several petal cut-and-paste experiments to test whether UV floral guides can also function to attract visitors. We manipulated floral guide size and evaluated visitation frequency. In all experiments, pollinator visitation rates were clearly associated with floral guide size. Diminished floral guides recruited relatively few insect visitors. Exaggerated floral guides recruited more visitors than smaller or average sized guides. Thus, UV floral guides play an important role in pollinator recruitment and in determining the relative attractiveness of conspecific flower heads. Consideration of floral guides is therefore important when evaluating the overall conspicuousness of flower heads relative to background coloration. This work raises the issue of whether floral guides serve as honest indicators of reward, since guide size varies in nature for conspecific flowers at the same developmental stage and since preferences for larger guides were found. To our knowledge, these are the first cut-and-paste experiments conducted to examine whether UV absorbent floral guides affect visitation rates and pollinator preference.

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Section: Discussionmentioning

confidence: 99%

Wild bees preferentially visitRudbeckiaflower heads with exaggerated ultraviolet absorbing floral guides

2014

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“…However, considering the high degree of variability that can be found in natural forest lights because of filtering effects (36), there will likely be cases, such as forest shade and open gaps environments, where any model will likely fail. This failure would explain behavioral observations that individual bumblebees show a tendency to prefer foraging within a constant illumination condition when finding colored flowers (20). How Would Such a System Operate?…”

Section: Significancementioning

confidence: 99%

“…Color signals captured in the bees' photoreceptors are sequentially processed along multiple neural pathways, including opponent neurons in the inner layer of the medulla, which seem to exhibit a capacity to adapt to stimulus input (19). Bumble bees are capable of sensing changes in overhead illumination and making complex foraging decisions (20)(21)(22), suggesting potential use of contextual information for perceiving variations in ambient illumination. For example, considering changes in the illumination from short to long wavelength-rich radiation, free flying bumblebees (23) and honey bees (17, 24) make reliable color decisions for most dynamic changing conditions.…”

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confidence: 99%

Improved color constancy in honey bees enabled by parallel visual projections from dorsal ocelli

Garcia

Hung

Greentree

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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How can a pollinator, like the honey bee, perceive the same colors on visited flowers, despite continuous and rapid changes in ambient illumination and background color? A hundred years ago, von Kries proposed an elegant solution to this problem, color constancy, which is currently incorporated in many imaging and technological applications. However, empirical evidence on how this method can operate on animal brains remains tenuous. Our mathematical modeling proposes that the observed spectral tuning of simple ocellar photoreceptors in the honey bee allows for the necessary input for an optimal color constancy solution to most natural light environments. The model is fully supported by our detailed description of a neural pathway allowing for the integration of signals originating from the ocellar photoreceptors to the information processing regions in the bee brain. These findings reveal a neural implementation to the classic color constancy problem that can be easily translated into artificial color imaging systems.daylight | insect | vision | neuron tracing | von Kries C olor constancy allows natural and artificial visual systems to solve the challenge of maintaining the color sensation of an object despite changes in the illumination. Color constancy requires the visual system to discount an unknown illumination function, when the only available information to a sensor may be the total response of the different photoreceptors present in the visual system (1).Color constancy by chromatic adaptation is classically modeled by assuming a set of scalar coefficients that adjust the sensitivity of the different sensors responsible for color vision depending on the particular ambient light conditions (2, 3). The chromatic effect produced by variation of the spectral power distribution (SPD) of daylight is explained by differences in the ratio of long to short wavelengths observed at different conditions of daylight (4). This variability is constrained, potentially making possible the recovery of SPD from a limited number of sensor responses and simplifying color constancy solutions (5). Indeed, it is possible to reconstruct the entire SPD for different phases of daylight with just two functions summarizing daylight variability at short (<550 nm) and long (>550 nm) wavelengths (6). However, visual targets often present complex shapes and textures and are illuminated by variable intensity, spectrally mixed illumination, potentially requiring the use of contextual information for achieving color constancy (7,8). Chromatic adaptation is thus thought unlikely to be the sole mechanism enabling constancy (8, 9), and different cortical or other neural processing mechanisms seem important for reliable color vision (10, 11). Considering human vision, color processing involves multistage neural representations from V1 to V4 and the frontal cortex, and although V4 neurons seem critical for automatic color constancy operations (11-14), subsequent neural processing stages have been implicated (15).Although this evidence suggests ...

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“…In montane systems, dipteran pollinators commonly increase in dominance with increasing elevation while hymenopterans increase with decreasing elevation (reviewed in Hodkinson 2005). Arnold and Chittka (2012) showed that bees displayed greater color discrimination in well-lit environments relative to shaded ones. Second, pollinator preference can change along an altitudinal gradient, irrespective of community composition.…”

Section: Introductionmentioning

confidence: 99%

An altitudinal cline in UV floral pattern corresponds with a behavioral change of a generalist pollinator assemblage

Koski

Ashman

2015

Ecology

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Spatial variation in pollinator communities or behaviors can underlie floral diversification. Floral traits in the UV spectrum are common and mediate plant-pollinator interactions, but the role of pollinators in driving or maintaining their geographic variation has not been fully explored. We identify an altitudinal cline of increasing relative size of the UV bullseye pattern in Argentina anserina (Rosaceae) flowers, and assess whether pollination context contributes to clinal variation. At four sites that varied in altitude, we document the pollinator assemblage, and pollinator preference and visitation behavior. We then determine how pollinator visits affected pollen receipt and export. Finally, we describe how the functional relationship between UV floral phenotype and pollen receipt changed with altitude. Floral UV bullseye size increased with altitude, which corresponded with a change from a hymenopteran- to a dipteran-dominated pollinator assemblage. While dipteran and hymenopteran preferences for bullseye size were similar, flowers with large bullseyes received more foraging visits than those with small bullseyes at higher altitude. The reverse was observed at the lower altitudes; pollinators approached large-bullseye flowers often but rarely foraged. These differences are expected to affect fitness because foraging visits increased pollen export and receipt. Indeed, when natural variation in bullseye size was considered, it had a stronger effect on pollen receipt than other traits (flower size, display, or color). Plants with larger bullseyes tended to receive more pollen at the highest-altitude site, while those with smaller ones received more pollen at the lowest-altitude site. Results suggest that altitudinal changes in preference and behavior of the overall pollinator assemblage, but not differential preferences of pollinator taxonomic groups, could contribute to clinal variation in a UV floral trait for a generalist-pollinated plant.

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Illumination preference, illumination constancy and colour discrimination by bumblebees in an environment with patchy light

Cited by 27 publications

References 25 publications

Wild bees preferentially visitRudbeckiaflower heads with exaggerated ultraviolet absorbing floral guides

Wild bees preferentially visitRudbeckiaflower heads with exaggerated ultraviolet absorbing floral guides

Improved color constancy in honey bees enabled by parallel visual projections from dorsal ocelli

An altitudinal cline in UV floral pattern corresponds with a behavioral change of a generalist pollinator assemblage

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