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Johanna Mappes - One of the best experts on this subject based on the ideXlab platform.
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Influences of geographic differentiation in the forewing Warning Signal of the wood tiger moth in Alaska
Evolutionary Ecology, 2014Co-Authors: Robert H. Hegna, Johanna MappesAbstract:Aposematic organisms have Warning Signals advertising their unpalatability to predators, and because Signal efficiency is better in higher densities, positive frequency-dependent selection is expected to select against less common Signals. The wood tiger moth ( Parasemia plantaginis ) occurs across the Holarctic and its conspicuous hindwings serve as Warning Signals to predators. It also has conspicuous black and white forewing patterns that could act as Warning Signals, or help to hide the moth by preventing predators from seeing the outline of the moth’s body (a strategy known as disruptive coloration). In Alaska, the predominant forewing pattern changes distinctly between the regions around Fairbanks and Anchorage, suggesting local predators may maintain differences if the pattern functions as a Warning Signal. Alternatively, restricted gene flow along with drift could be responsible. We placed artificial moths with both local dominant and foreign forewing patterns in each of the two regions to test if predators select against the foreign forewing types, which would suggest the Warning Signal function of forewing patters. We also manipulated the level of disruptiveness in the forewing patterns to see if disruptiveness works in concert with the Warning Signal. The locally dominant forewing type was better protected in Fairbanks, but not in Anchorage where morphs were attacked equally. Manipulating the level of disruptiveness in the forewing pattern did not influence predation. Population genetic analyses from specimens caught during fieldwork showed the existence of two populations and restricted gene flow. Our results suggest that positive frequency dependent selection may be partially responsible for maintaining local Signal differences, although predators seem to avoid both forewing patterns in Anchorage. Restricted gene flow between the two populations could be attributed to a combination of selection against foreign morphs in Fairbanks and physical barriers, which both likely contribute to Warning Signal differences in Alaska.
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Temporal relationship between genetic and Warning Signal variation in the aposematic wood tiger moth (Parasemia plantaginis)
Molecular ecology, 2014Co-Authors: Juan A. Galarza, Robert H. Hegna, Ossi Nokelainen, Roghaeih Ashrafi, Johanna MappesAbstract:Many plants and animals advertise unpalatability through Warning Signals in the form of colour and shape. Variation in Warning Signals within local populations is not expected because they are subject to directional selection. However, mounting evidence of Warning Signal variation within local populations suggests that other selective forces may be acting. Moreover, different selective pressures may act on the individual components of a Warning Signal. At present, we have a limited understanding about how multiple selection processes operate simultaneously on Warning Signal components, and even less about their temporal and spatial dynamics. Here, we examined temporal variation of several wing Warning Signal components (colour, UV-reflectance, Signal size and pattern) of two co-occurring colour morphs of the aposematic wood tiger moth (Parasemia plantaginis). Sampling was carried out in four geographical regions over three consecutive years. We also evaluated each morph's temporal genetic structure by analysing mitochondrial sequence data and nuclear microsatellite markers. Our results revealed temporal differences between the morphs for most Signal components measured. Moreover, variation occurred differently in the fore- and hindwings. We found no differences in the genetic structure between the morphs within years and regions, suggesting single local populations. However, local genetic structure fluctuated temporally. Negative correlations were found between variation produced by neutrally evolving genetic markers and those of the different Signal components, indicating a non-neutral evolution for most Warning Signal components. Taken together, our results suggest that differential selection on Warning Signal components and fluctuating population structure can be one explanation for the maintenance of Warning Signal variation in this aposematic species.
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to quiver or to shiver increased melanization benefits thermoregulation but reduces Warning Signal efficacy in the wood tiger moth
Proceedings of The Royal Society B: Biological Sciences, 2013Co-Authors: Robert H. Hegna, Ossi Nokelainen, Jonathan R Hegna, Johanna MappesAbstract:Melanin production is often considered costly, yet beneficial for thermoregulation. Studies of variation in melanization and the opposing selective forces that underlie its variability contribute greatly to understanding natural selection. We investigated whether melanization benefits are traded off with predation risk to promote observed local and geographical variation in the Warning Signal of adult male wood tiger moths (Parasemia plantaginis). Warning Signal variation is predicted to reduce survival in aposematic species. However, in P. plantaginis, male hindwings are either yellow or white in Europe, and show continuous variation in melanized markings that cover 20 to 90 per cent of the hindwing. We found that the amount of melanization increased from 40 to 59 per cent between Estonia (58° N) and north Finland (67° N), suggesting melanization carries thermoregulatory benefits. Our thermal measurements showed that more melanic individuals warmed up more quickly on average than less melanic individuals, which probably benefits flight in cold temperatures. With extensive field experiments in central Finland and the Alpine region, we found that more melanic individuals suffered increased predation. Together, our data suggest that Warning Signal efficiency is constrained by thermoregulatory benefits. Differences in relative costs and benefits of melanin probably help to maintain the geographical Warning Signal differences.
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trade off between Warning Signal efficacy and mating success in the wood tiger moth
Proceedings of The Royal Society B: Biological Sciences, 2012Co-Authors: Ossi Nokelainen, Robert H. Hegna, Carita Lindstedt, Joanneke H Reudler, Johanna MappesAbstract:The coloration of species can have multiple functions, such as predator avoidance and sexual Signalling, that directly affect fitness. As selection should favour traits that positively affect fitness, the genes underlying the trait should reach fixation, thereby preventing the evolution of polymorphisms. This is particularly true for aposematic species that rely on coloration as a Warning Signal to advertise their unprofitability to predators. Nonetheless, there are numerous examples of aposematic species showing remarkable colour polymorphisms. We examined whether colour polymorphism in the wood tiger moth is maintained by trade-offs between different functions of coloration. In Finland, males of this species have two distinct colour morphs: white and yellow. The efficacy of the Warning Signal of these morphs was tested by offering them to blue tits in the laboratory. Birds hesitated significantly longer to attack yellow than white males. In a field experiment, the survival of the yellow males was also higher than white males. However, mating experiments in the laboratory revealed that yellow males had lower mating success than white males. Our results offer an explanation for the maintenance of polymorphism via trade-off between survival selection and mating success.
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Prey community structure affects how predators select for Müllerian mimicry
Proceedings. Biological sciences, 2012Co-Authors: Eira Ihalainen, Graeme D. Ruxton, Michael P. Speed, Hannah M. Rowland, Johanna MappesAbstract:Mullerian mimicry describes the close resemblance between aposematic prey species; it is thought to be beneficial because sharing a Warning Signal decreases the mortality caused by sampling by inex...
Robert H. Hegna - One of the best experts on this subject based on the ideXlab platform.
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Influences of geographic differentiation in the forewing Warning Signal of the wood tiger moth in Alaska
Evolutionary Ecology, 2014Co-Authors: Robert H. Hegna, Johanna MappesAbstract:Aposematic organisms have Warning Signals advertising their unpalatability to predators, and because Signal efficiency is better in higher densities, positive frequency-dependent selection is expected to select against less common Signals. The wood tiger moth ( Parasemia plantaginis ) occurs across the Holarctic and its conspicuous hindwings serve as Warning Signals to predators. It also has conspicuous black and white forewing patterns that could act as Warning Signals, or help to hide the moth by preventing predators from seeing the outline of the moth’s body (a strategy known as disruptive coloration). In Alaska, the predominant forewing pattern changes distinctly between the regions around Fairbanks and Anchorage, suggesting local predators may maintain differences if the pattern functions as a Warning Signal. Alternatively, restricted gene flow along with drift could be responsible. We placed artificial moths with both local dominant and foreign forewing patterns in each of the two regions to test if predators select against the foreign forewing types, which would suggest the Warning Signal function of forewing patters. We also manipulated the level of disruptiveness in the forewing patterns to see if disruptiveness works in concert with the Warning Signal. The locally dominant forewing type was better protected in Fairbanks, but not in Anchorage where morphs were attacked equally. Manipulating the level of disruptiveness in the forewing pattern did not influence predation. Population genetic analyses from specimens caught during fieldwork showed the existence of two populations and restricted gene flow. Our results suggest that positive frequency dependent selection may be partially responsible for maintaining local Signal differences, although predators seem to avoid both forewing patterns in Anchorage. Restricted gene flow between the two populations could be attributed to a combination of selection against foreign morphs in Fairbanks and physical barriers, which both likely contribute to Warning Signal differences in Alaska.
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Temporal relationship between genetic and Warning Signal variation in the aposematic wood tiger moth (Parasemia plantaginis)
Molecular ecology, 2014Co-Authors: Juan A. Galarza, Robert H. Hegna, Ossi Nokelainen, Roghaeih Ashrafi, Johanna MappesAbstract:Many plants and animals advertise unpalatability through Warning Signals in the form of colour and shape. Variation in Warning Signals within local populations is not expected because they are subject to directional selection. However, mounting evidence of Warning Signal variation within local populations suggests that other selective forces may be acting. Moreover, different selective pressures may act on the individual components of a Warning Signal. At present, we have a limited understanding about how multiple selection processes operate simultaneously on Warning Signal components, and even less about their temporal and spatial dynamics. Here, we examined temporal variation of several wing Warning Signal components (colour, UV-reflectance, Signal size and pattern) of two co-occurring colour morphs of the aposematic wood tiger moth (Parasemia plantaginis). Sampling was carried out in four geographical regions over three consecutive years. We also evaluated each morph's temporal genetic structure by analysing mitochondrial sequence data and nuclear microsatellite markers. Our results revealed temporal differences between the morphs for most Signal components measured. Moreover, variation occurred differently in the fore- and hindwings. We found no differences in the genetic structure between the morphs within years and regions, suggesting single local populations. However, local genetic structure fluctuated temporally. Negative correlations were found between variation produced by neutrally evolving genetic markers and those of the different Signal components, indicating a non-neutral evolution for most Warning Signal components. Taken together, our results suggest that differential selection on Warning Signal components and fluctuating population structure can be one explanation for the maintenance of Warning Signal variation in this aposematic species.
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Not all colors are equal: predation and color polytypism in the aposematic poison frog Oophaga pumilio
Evolutionary Ecology, 2013Co-Authors: Robert H. Hegna, Ralph A. Saporito, Maureen A DonnellyAbstract:Aposematic organisms are not predicted to show high levels of Warning Signal diversity because they are expected to be under stabilizing selection to decrease costs of ‘educating’ predators about their unpalatability. However, systematic changes in Warning Signals (polytypism) can be expected if they represent adaptations to local predators. The aposematic strawberry poison frog ( Oophaga pumilio ) is red throughout its mainland distribution in Costa Rica and Panamá, but displays high levels of Warning Signal diversity in the Bocas del Toro Archipelago of Panamá. Both coloration and spot pattern vary in a polytypic sense. Sexual selection contributes to maintaining the polytypism, but little work has investigated the potential influence of predation. We used unspotted models of O. pumilio to determine if predation might help explain the color polytypism on Isla Colón in the Bocas del Toro Archipelago of Panamá. We tested whether attack rates differed among the red mainland morph, green/yellow Isla Colón morph, and the brown control. We found that frog color significantly predicted being attacked. The local green Isla Colón models were attacked more than foreign red or brown models. No difference in attack rate existed between red and brown control models. Our results suggest that the red mainland morph possesses a more effective Warning Signal, even when it is not the local morph. Honest Signaling of unpalatability, neophobia, and the use of search images by local predators are potential explanations. Similarity of the brown model to other local poison frogs might explain the lower attack rate compared to previous work. The attack rate was lower on Isla Colón compared to mainland Costa Rica, which supports the hypothesis that less overall predation in the Bocas del Toro Archipelago may contribute to the overall Warning Signal diversity in O. pumilio there by relaxing selection for aposematic traits.
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to quiver or to shiver increased melanization benefits thermoregulation but reduces Warning Signal efficacy in the wood tiger moth
Proceedings of The Royal Society B: Biological Sciences, 2013Co-Authors: Robert H. Hegna, Ossi Nokelainen, Jonathan R Hegna, Johanna MappesAbstract:Melanin production is often considered costly, yet beneficial for thermoregulation. Studies of variation in melanization and the opposing selective forces that underlie its variability contribute greatly to understanding natural selection. We investigated whether melanization benefits are traded off with predation risk to promote observed local and geographical variation in the Warning Signal of adult male wood tiger moths (Parasemia plantaginis). Warning Signal variation is predicted to reduce survival in aposematic species. However, in P. plantaginis, male hindwings are either yellow or white in Europe, and show continuous variation in melanized markings that cover 20 to 90 per cent of the hindwing. We found that the amount of melanization increased from 40 to 59 per cent between Estonia (58° N) and north Finland (67° N), suggesting melanization carries thermoregulatory benefits. Our thermal measurements showed that more melanic individuals warmed up more quickly on average than less melanic individuals, which probably benefits flight in cold temperatures. With extensive field experiments in central Finland and the Alpine region, we found that more melanic individuals suffered increased predation. Together, our data suggest that Warning Signal efficiency is constrained by thermoregulatory benefits. Differences in relative costs and benefits of melanin probably help to maintain the geographical Warning Signal differences.
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trade off between Warning Signal efficacy and mating success in the wood tiger moth
Proceedings of The Royal Society B: Biological Sciences, 2012Co-Authors: Ossi Nokelainen, Robert H. Hegna, Carita Lindstedt, Joanneke H Reudler, Johanna MappesAbstract:The coloration of species can have multiple functions, such as predator avoidance and sexual Signalling, that directly affect fitness. As selection should favour traits that positively affect fitness, the genes underlying the trait should reach fixation, thereby preventing the evolution of polymorphisms. This is particularly true for aposematic species that rely on coloration as a Warning Signal to advertise their unprofitability to predators. Nonetheless, there are numerous examples of aposematic species showing remarkable colour polymorphisms. We examined whether colour polymorphism in the wood tiger moth is maintained by trade-offs between different functions of coloration. In Finland, males of this species have two distinct colour morphs: white and yellow. The efficacy of the Warning Signal of these morphs was tested by offering them to blue tits in the laboratory. Birds hesitated significantly longer to attack yellow than white males. In a field experiment, the survival of the yellow males was also higher than white males. However, mating experiments in the laboratory revealed that yellow males had lower mating success than white males. Our results offer an explanation for the maintenance of polymorphism via trade-off between survival selection and mating success.
Carita Lindstedt - One of the best experts on this subject based on the ideXlab platform.
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trade off between Warning Signal efficacy and mating success in the wood tiger moth
Proceedings of The Royal Society B: Biological Sciences, 2012Co-Authors: Ossi Nokelainen, Robert H. Hegna, Carita Lindstedt, Joanneke H Reudler, Johanna MappesAbstract:The coloration of species can have multiple functions, such as predator avoidance and sexual Signalling, that directly affect fitness. As selection should favour traits that positively affect fitness, the genes underlying the trait should reach fixation, thereby preventing the evolution of polymorphisms. This is particularly true for aposematic species that rely on coloration as a Warning Signal to advertise their unprofitability to predators. Nonetheless, there are numerous examples of aposematic species showing remarkable colour polymorphisms. We examined whether colour polymorphism in the wood tiger moth is maintained by trade-offs between different functions of coloration. In Finland, males of this species have two distinct colour morphs: white and yellow. The efficacy of the Warning Signal of these morphs was tested by offering them to blue tits in the laboratory. Birds hesitated significantly longer to attack yellow than white males. In a field experiment, the survival of the yellow males was also higher than white males. However, mating experiments in the laboratory revealed that yellow males had lower mating success than white males. Our results offer an explanation for the maintenance of polymorphism via trade-off between survival selection and mating success.
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Characterizing the pigment composition of a variable Warning Signal of Parasemia plantaginis larvae
Functional Ecology, 2010Co-Authors: Carita Lindstedt, Leena Lindström, Nathan Morehouse, Hannu Pakkanen, Jérôme Casas, Jean-philippe Christidès, Kimmo Kemppainen, Johanna MappesAbstract:1. Aposematic animals advertise their defences to predators via Warning Signals that often are bright colours combined with black patterns. Predation is assumed to select for large pattern elements and conspicuousness of Warning Signals because this enhances avoidance learning of predators. However, conspicuousness of the colour pattern can vary among individuals of aposematic species, suggesting that Warning Signal expression may be constrained by opposing selection pressures. If effective Warning Signals are costly to produce, variation in Signal expression may be maintained via physiological trade-offs. To understand the costs of Signalling that might underlay both physiological and ecological trade-offs, it is crucial to identify the pigments involved in aposematic traits, how they or their precursors are acquired and how their production and ⁄ or deposition interact with other physiological processes. 2. We characterized the pigments responsible for the genetically and phenotypically variable orange-black Warning Signal of the hairy larvae of an Arctiid moth, Parasemia plantaginis. We tested orange and black coloured hairs for the presence of six candidate pigment types using high-performance liquid chromatography, spectral and solubility analyses. 3. After excluding the presence of carotenoids, ommochromes, pterins and pheomelanins in orange hairs, our results suggest that tiger moth larvae produce their orange Warning Signal by depositing both diet-derived flavonoids and trace levels of synthesized eumelanin in their hairs. The nearby black hairs are coloured by eumelanin. 4. In light of previous studies, we conclude that although a large orange patch increases the 1larvae's antipredator efficacy, variation in the size of orange patches within a population can be driven by scarcity of flavonoids in diet. However, traces of eumelanin found in the orange hairs of the larvae may also play a significant role in the maintenance of the Signal pattern on poor quality diets. 5. The goal of the future studies will be to test the condition dependence of pigment deposition in aposematic colour patterns by directly manipulating relevant nutritional parameters such as dietary flavonoid or nitrogen content (i.e. amino acid content).
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Thermoregulation constrains effective Warning Signal expression.
Evolution; international journal of organic evolution, 2008Co-Authors: Carita Lindstedt, Leena Lindström, Johanna MappesAbstract:Evolution of conspicuous Signals may be constrained if animal coloration has nonSignaling as well as Signaling functions. In aposematic wood tiger moth (Parasemia plantaginis) larvae, the size of a Warning Signal (orange patch on black body) varies phenotypically and genetically. Although a large Warning Signal is favored as an antipredator defense, we hypothesized that thermoregulation may constrain the Signal size in colder habitats. To test this hypothesis, we conducted a factorial rearing experiment with two selection lines for larval coloration (small and large Signal) and with two temperature manipulations (high and low temperature environment). Temperature constrained the size and brightness of the Warning Signal. Larvae with a small Signal had an advantage in the colder environment, which was demonstrated by a faster development time and growth rate in the low temperature treatment, compared to larvae with a large Signal. Interestingly, the larvae with a small Signal were found more often on the plant than the ones with a large Signal, suggesting higher basking activity of the melanic (small Signal) individuals in the low temperature. We conclude that the expression of aposematic display is not only defined by its efficacy against predators; variation in temperature may constrain evolution of a conspicuous Warning Signal and maintain variation in it.
Ronald L. Rutowski - One of the best experts on this subject based on the ideXlab platform.
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Effects of directionality, Signal intensity, and short-wavelength components on iridescent Warning Signal efficacy
Behavioral Ecology and Sociobiology, 2016Co-Authors: Kimberly V. Pegram, Ronald L. RutowskiAbstract:Many bright colors function as visual Signals and are produced by structural mechanisms that result in their being iridescent. Iridescent colors differ from other types of animal coloration in that they vary in both hue and intensity, as the angle of viewing and illumination change relative to the color surface. Iridescent colors can serve as Warning Signals by deterring predation on distasteful animals. Due to their directional and mirror-like reflection, iridescent Signals have the potential to (1) vary in appearance with each approach; (2) create a flashing Signal; (3) under the right conditions, be more intense than diffusely reflecting Signals; (4) display different hues with different positioning of the sun, predator, and prey; and (5) display angle-dependent camouflage, which could all influence Warning Signal effectiveness. Here, we examine how Signal intensity, short-wavelength hue, and variation in appearance affect the response of domestic chickens ( Gallus gallus domesticus ) to Warning Signals. Variation did not affect their response. Higher intensity Signals were more effective in terms of predator avoidance than were lower intensity, and blue-violet Signals were more effective than were blue and blue-green. This could influence the effectiveness of an iridescent Warning Signal in nature if the prey displays more intense, blue-violet coloration. With the properties we tested, we found no cost to having Warning colors that are iridescent and that there may be benefits in the ability to change hue and display a more intense Signal. We suggest future research to examine the effects of iridescent flashing and angle-dependent camouflage on Warning Signal effectiveness. Significance statement Iridescent colors have only been recently shown to function as Warning Signals, but we know very little about how they function to deter predation. Here, we show that birds are more likely to change their behavior in response to higher intensity and blue-violet Signals compared to low intensity and blue and blue-green Signals. The intensity results are consistent with previous experiments, but the role of short-wavelength hue on Warning Signal effectiveness has never been tested before. Variation due to the shifting appearance of an iridescent Signal did not influence the response to the Warning Signal, consistent with studies in long-wavelength Signals. We found no cost to displaying an iridescent Signal and potentially an adaptive benefit as iridescent Warning Signals have the potential to be brighter and display a different hue based on the arrangement of light source, Signaler, and receiver.
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Effects of directionality, Signal intensity, and short-wavelength components on iridescent Warning Signal efficacy
Behavioral Ecology and Sociobiology, 2016Co-Authors: Kimberly V. Pegram, Ronald L. RutowskiAbstract:Many bright colors function as visual Signals and are produced by structural mechanisms that result in their being iridescent. Iridescent colors differ from other types of animal coloration in that they vary in both hue and intensity, as the angle of viewing and illumination change relative to the color surface. Iridescent colors can serve as Warning Signals by deterring predation on distasteful animals. Due to their directional and mirror-like reflection, iridescent Signals have the potential to (1) vary in appearance with each approach; (2) create a flashing Signal; (3) under the right conditions, be more intense than diffusely reflecting Signals; (4) display different hues with different positioning of the sun, predator, and prey; and (5) display angle-dependent camouflage, which could all influence Warning Signal effectiveness. Here, we examine how Signal intensity, short-wavelength hue, and variation in appearance affect the response of domestic chickens (Gallus gallus domesticus) to Warning Signals. Variation did not affect their response. Higher intensity Signals were more effective in terms of predator avoidance than were lower intensity, and blue-violet Signals were more effective than were blue and blue-green. This could influence the effectiveness of an iridescent Warning Signal in nature if the prey displays more intense, blue-violet coloration. With the properties we tested, we found no cost to having Warning colors that are iridescent and that there may be benefits in the ability to change hue and display a more intense Signal. We suggest future research to examine the effects of iridescent flashing and angle-dependent camouflage on Warning Signal effectiveness. Iridescent colors have only been recently shown to function as Warning Signals, but we know very little about how they function to deter predation. Here, we show that birds are more likely to change their behavior in response to higher intensity and blue-violet Signals compared to low intensity and blue and blue-green Signals. The intensity results are consistent with previous experiments, but the role of short-wavelength hue on Warning Signal effectiveness has never been tested before. Variation due to the shifting appearance of an iridescent Signal did not influence the response to the Warning Signal, consistent with studies in long-wavelength Signals. We found no cost to displaying an iridescent Signal and potentially an adaptive benefit as iridescent Warning Signals have the potential to be brighter and display a different hue based on the arrangement of light source, Signaler, and receiver.
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iridescent blue and orange components contribute to the recognition of a multicomponent Warning Signal
Behaviour, 2013Co-Authors: Kimberly V. Pegram, Melissa J Lillo, Ronald L. RutowskiAbstract:Warning colouration functions to deter predators from attacking unprofitable (e.g., unpalatable or toxic) prey items. While Warning colours are often characterized by long-wavelength components (e.g., orange, red or yellow), many distasteful animals across the animal kingdom display orange or red colour patches adjacent to or within a field of short-wavelength colouration such as blue (e.g., strawberry poison dart frogs, pipevine swallowtail and pyjama nudibranch), which yields a multicomponent visual Warning Signal. Here we show that, in such Signals, blue and orange patches can function as redundant Signal components; avian predators trained not to attack the intact blue and orange colouration of the pipevine swallowtail (Battus philenor) recognised the butterflies as distasteful even when the blue and orange were presented individually. Our results demonstrate that blue colouration and potential multiple, unimodal, Signal components should be considered in research on visual Warning Signals, including in well-studied animals, such as dendrobatid frogs and swallowtail butterflies.
Kimberly V. Pegram - One of the best experts on this subject based on the ideXlab platform.
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Effects of directionality, Signal intensity, and short-wavelength components on iridescent Warning Signal efficacy
Behavioral Ecology and Sociobiology, 2016Co-Authors: Kimberly V. Pegram, Ronald L. RutowskiAbstract:Many bright colors function as visual Signals and are produced by structural mechanisms that result in their being iridescent. Iridescent colors differ from other types of animal coloration in that they vary in both hue and intensity, as the angle of viewing and illumination change relative to the color surface. Iridescent colors can serve as Warning Signals by deterring predation on distasteful animals. Due to their directional and mirror-like reflection, iridescent Signals have the potential to (1) vary in appearance with each approach; (2) create a flashing Signal; (3) under the right conditions, be more intense than diffusely reflecting Signals; (4) display different hues with different positioning of the sun, predator, and prey; and (5) display angle-dependent camouflage, which could all influence Warning Signal effectiveness. Here, we examine how Signal intensity, short-wavelength hue, and variation in appearance affect the response of domestic chickens ( Gallus gallus domesticus ) to Warning Signals. Variation did not affect their response. Higher intensity Signals were more effective in terms of predator avoidance than were lower intensity, and blue-violet Signals were more effective than were blue and blue-green. This could influence the effectiveness of an iridescent Warning Signal in nature if the prey displays more intense, blue-violet coloration. With the properties we tested, we found no cost to having Warning colors that are iridescent and that there may be benefits in the ability to change hue and display a more intense Signal. We suggest future research to examine the effects of iridescent flashing and angle-dependent camouflage on Warning Signal effectiveness. Significance statement Iridescent colors have only been recently shown to function as Warning Signals, but we know very little about how they function to deter predation. Here, we show that birds are more likely to change their behavior in response to higher intensity and blue-violet Signals compared to low intensity and blue and blue-green Signals. The intensity results are consistent with previous experiments, but the role of short-wavelength hue on Warning Signal effectiveness has never been tested before. Variation due to the shifting appearance of an iridescent Signal did not influence the response to the Warning Signal, consistent with studies in long-wavelength Signals. We found no cost to displaying an iridescent Signal and potentially an adaptive benefit as iridescent Warning Signals have the potential to be brighter and display a different hue based on the arrangement of light source, Signaler, and receiver.
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Effects of directionality, Signal intensity, and short-wavelength components on iridescent Warning Signal efficacy
Behavioral Ecology and Sociobiology, 2016Co-Authors: Kimberly V. Pegram, Ronald L. RutowskiAbstract:Many bright colors function as visual Signals and are produced by structural mechanisms that result in their being iridescent. Iridescent colors differ from other types of animal coloration in that they vary in both hue and intensity, as the angle of viewing and illumination change relative to the color surface. Iridescent colors can serve as Warning Signals by deterring predation on distasteful animals. Due to their directional and mirror-like reflection, iridescent Signals have the potential to (1) vary in appearance with each approach; (2) create a flashing Signal; (3) under the right conditions, be more intense than diffusely reflecting Signals; (4) display different hues with different positioning of the sun, predator, and prey; and (5) display angle-dependent camouflage, which could all influence Warning Signal effectiveness. Here, we examine how Signal intensity, short-wavelength hue, and variation in appearance affect the response of domestic chickens (Gallus gallus domesticus) to Warning Signals. Variation did not affect their response. Higher intensity Signals were more effective in terms of predator avoidance than were lower intensity, and blue-violet Signals were more effective than were blue and blue-green. This could influence the effectiveness of an iridescent Warning Signal in nature if the prey displays more intense, blue-violet coloration. With the properties we tested, we found no cost to having Warning colors that are iridescent and that there may be benefits in the ability to change hue and display a more intense Signal. We suggest future research to examine the effects of iridescent flashing and angle-dependent camouflage on Warning Signal effectiveness. Iridescent colors have only been recently shown to function as Warning Signals, but we know very little about how they function to deter predation. Here, we show that birds are more likely to change their behavior in response to higher intensity and blue-violet Signals compared to low intensity and blue and blue-green Signals. The intensity results are consistent with previous experiments, but the role of short-wavelength hue on Warning Signal effectiveness has never been tested before. Variation due to the shifting appearance of an iridescent Signal did not influence the response to the Warning Signal, consistent with studies in long-wavelength Signals. We found no cost to displaying an iridescent Signal and potentially an adaptive benefit as iridescent Warning Signals have the potential to be brighter and display a different hue based on the arrangement of light source, Signaler, and receiver.
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iridescent blue and orange components contribute to the recognition of a multicomponent Warning Signal
Behaviour, 2013Co-Authors: Kimberly V. Pegram, Melissa J Lillo, Ronald L. RutowskiAbstract:Warning colouration functions to deter predators from attacking unprofitable (e.g., unpalatable or toxic) prey items. While Warning colours are often characterized by long-wavelength components (e.g., orange, red or yellow), many distasteful animals across the animal kingdom display orange or red colour patches adjacent to or within a field of short-wavelength colouration such as blue (e.g., strawberry poison dart frogs, pipevine swallowtail and pyjama nudibranch), which yields a multicomponent visual Warning Signal. Here we show that, in such Signals, blue and orange patches can function as redundant Signal components; avian predators trained not to attack the intact blue and orange colouration of the pipevine swallowtail (Battus philenor) recognised the butterflies as distasteful even when the blue and orange were presented individually. Our results demonstrate that blue colouration and potential multiple, unimodal, Signal components should be considered in research on visual Warning Signals, including in well-studied animals, such as dendrobatid frogs and swallowtail butterflies.
