Flower Color Evolution and the Evidence of Pollinator-Mediated Selection

Trunschke, Judith; Lunau, Klaus; Pyke, Graham H.; Ren, Zhoupeng; Wang, Hong

doi:10.3389/fpls.2021.617851

Cited by 56 publications

(48 citation statements)

References 141 publications

(295 reference statements)

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“…An unanswered question for the system is whether any C. angustifolium visitors perceive the reflectance variation from the petals or if it matters. Additionally, it is possible pollinators may respond to visual signals that were not represented by our point measure of spectral reflectance, such as ultraviolet patterns (Koski and Ashman, 2014;Trunschke et al, 2021). While we only measured a single petal per flower, to our knowledge there are no UV patterns on C. angustifolium petals (Kaz Ohashi, personal communication) and the low reflectance in the 300-400 nm range also supports this interpretation.…”

Section: Discussionmentioning

confidence: 66%

Differences in Floral Scent and Petal Reflectance Between Diploid and Tetraploid Chamerion angustifolium

2021

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Genome duplication in plants is thought to be a route to speciation due to cytotype incompatibility. However, to reduce cross-pollination between cytotypes in animal-pollinated species, distinctive floral phenotypes, which would allow pollinator-mediated assortative mating between flowers, are also expected. Chamerion angustifolium is a Holarctic species that forms a hybrid zone between diploid and tetraploid populations in the North American Rocky Mountains. Extensive research has shown that these cytotypes differ in many ways, including some floral traits, and that pollinators can discriminate between cytotypes, leading to assortative mating. However, two signals commonly used by insect pollinators have not been measured for this species, namely petal colour and floral scent. Using greenhouse-grown diploids and tetraploids of C. angustifolium from the ploidy hybrid-zone in the North American Rocky Mountains, we show that both floral scent signals and petal reflectance differ between cytotypes. These differences, along with differences in flower size shown previously, could help explain pollinator-mediated assortative mating observed in previous studies. However, these differences in floral phenotypes may vary in importance to pollinators. While the differences in scent included common floral volatiles readily detected by bumblebees, the differences in petal reflectance may not be perceived by bees based on their visual sensitivity across the spectra. Thus, our results suggest that differences in floral volatile emissions are more likely to contribute to pollinator discrimination between cytotypes and highlight the importance of understanding the sensory systems of pollinators when examining floral signals.

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Section: Discussionmentioning

confidence: 66%

Differences in Floral Scent and Petal Reflectance Between Diploid and Tetraploid Chamerion angustifolium

2021

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“…Likewise, some flying pollinators ( e.g ., honeybees and butterflies) also use achromatic intensity contrast especially when the targets are small ( Koshitaka, Arikawa & Kinoshita, 2011 ; Dyer, Spaethe & Prack, 2008 ). Additionally, different components of the flower-visitor-subjective color appearance of flowers must be distinguished ( e.g ., hue, saturation, brightness, and other potentially visible characteristics) for correctly identifying possible selection targets, as demonstrated by laboratory studies ( Trunschke et al, 2021 ). In addition, flower visits include a sequence of behavioral reactions, which can be driven by innate bias.…”

Section: Discussionmentioning

confidence: 97%

“…As such, learning to associate floral cues with the presence of a reward could increase foraging efficiency if it allows the pollinator to locate a new flower of the same species and quickly extract the nectar. Floral color plays an essential role in this task ( Trunschke et al, 2021 ). In contrast, innate preferences—which have been extensively investigated in flower-visiting social insects ( Lunau & Maier, 1995 ; Kelber, Vorobyev & Osorio, 2003 )—are believed to account for biases that aid in recognition, and possibly learning, of critical floral resources ( Riffell et al, 2008 ).…”

Section: Introductionmentioning

confidence: 99%

Innate and learnt color preferences in the common green-eyed white butterfly (Leptophobia aripa): experimental evidence

Muñoz-Galicia¹,

Castillo‐Guevara²,

Lara³

2021

PeerJ

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Background Learning abilities help animals modify their behaviors based on experience and innate sensory biases to confront environmental unpredictability. In a food acquisition context, the ability to detect, learn, and switch is fundamental in a wide range of insect species facing the ever-changing availability of their floral rewards. Here, we used an experimental approach to address the innate color preferences and learning abilities of the common green-eyed white butterfly (Leptophobia aripa). Methods In Experiment 1, we conducted innate preference choice-tests to determine whether butterflies had a strong innate color preference and to evaluate whether color preferences differed depending on the array of colors offered. We faced naïve butterflies to artificial flowers of four colors (quadruple choice-test): yellow, pink, white, and red; their choices were assessed. In Experiment 2, we examined the ability of this butterfly species to associate colors with rewards while exploring if the spectral reflectance value of a flower color can slow or accelerate this behavioral response. Butterflies were first trained to be fed from artificial yellow flowers inserted in a feeder. These were later replaced by artificial flowers with a similar (blue) or very different (white) spectral reflectance range. Each preference test comprised a dual-choice test (yellow vs blue, yellow vs white). Results Butterflies showed an innate strong preference for red flowers. Both the number of visits and the time spent probing these flowers were much greater than the pink, white, and yellow color flowers. Butterflies learn to associate colors with sugar rewards. They then learned the newly rewarded colors as quickly and proficiently as if the previously rewarded color was similar in spectral reflectance value; the opposite occurs if the newly rewarded color is very different than the previously rewarded color. Conclusions Our findings suggest that common green-eyed white butterflies have good learning abilities. These capabilities may allow them to respond rapidly to different color stimulus.

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“…While it can be assumed that many of the flower visitors also serve as pollinators, experimental proof of the actual pollinator identity and its share in the overall pollination of most generalist plant species is largely lacking. These bits of information are, however, crucial in understanding pollinator-mediated selection on traits like e.g., color, since the strength of selection can be assumed to critically depend on the pollination efficiency of the different pollinators of a plant species (Trunschke et al, 2021). To better understand the origin of the color frequency distribution that we observed in our study, we need further detailed information about the base line in the entire community (i.e., spectral reflectance data from all of the c. 400 flowering plant species that occur in the region) and quality information about the predominant pollinator(s) for each of them, which will be a challenge for future generations of pollination ecologists.…”

Section: Colormentioning

confidence: 99%

Flower Color as Predictor for Nectar Reward Quantity in an Alpine Flower Community

Streinzer

Neumayer²,

Spaethe

2021

Front. Ecol. Evol.

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Entomophilous plants have evolved colorful floral displays to attract flower visitors to achieve pollination. Although many insects possess innate preferences for certain colors, the underlying proximate and ultimate causes for this behavior are still not well understood. It has been hypothesized that the floral rewards, e.g., sugar content, of plants belonging to a particular color category correlate with the preference of the flower visitors. However, this hypothesis has been tested only for a subset of plant communities worldwide. Bumble bees are the most important pollinators in alpine environments and show a strong innate preference for (bee) “UV-blue” and “blue” colors. We surveyed plants visited by bumble bees in the subalpine and alpine zones (>1,400 m a.s.l.) of the Austrian Alps and measured nectar reward and spectral reflectance of the flowers. We found that the majority of the 105 plant samples visited by bumble bees fall into the color categories “blue” and “blue-green” of a bee-specific color space. Our study shows that color category is only a weak indicator for nectar reward quantity; and due to the high reward variance within and between categories, we do not consider floral color as a reliable signal for bumble bees in the surveyed habitat. Nevertheless, since mean floral reward quantity differs between categories, naïve bumble bees may benefit from visiting flowers that fall into the innately preferred color category during their first foraging flights.

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Flower Color Evolution and the Evidence of Pollinator-Mediated Selection

Cited by 56 publications

References 141 publications

Differences in Floral Scent and Petal Reflectance Between Diploid and Tetraploid Chamerion angustifolium

Differences in Floral Scent and Petal Reflectance Between Diploid and Tetraploid Chamerion angustifolium

Innate and learnt color preferences in the common green-eyed white butterfly (Leptophobia aripa): experimental evidence

Flower Color as Predictor for Nectar Reward Quantity in an Alpine Flower Community

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