Lisa Taylor, Nate Morehouse and I are organizing a symposium entitled "Color signals in terrestrial invertebrates: integrating senders and receivers" at ISBE next week. I collected the symposium abstracts here for easy reference, in order of presentation. The full abstract book of ISBE 2014 can be found at http://www.isbe2014.com.
Zurek DB*, Taylor LA, Byrne K, Cronin TW, Morehouse NI: Color vision in a colorful predator: light path absorbance and retinal sensitivities in jumping spiders
The spider family Salticidae (Jumping spiders) offers immense potential for the study of visually guided behavior and visual signal evolution due to their complex visual systems, sophisticated behavioral repertoires, and high ecological and species diversity. Behavioral evidence suggests that color plays a major role in the lives of these animals, including the identification of suitable prey and the selection of attractive mates. However, a number of key questions remain regarding how this group of animals sees color. Previous work has established that color vision is enabled by the large forward-facing principal eyes, but comprehensive characterization of visual sensitivities has proved challenging to access using traditional methods. The small number of available studies hints at considerable species diversity in wavelength sensitivities. By using an MSP-based approach, a first in arachnids, we characterized spectral transmission profiles of photoreceptors, as well as of pre-retinal optical elements in the principal eyes of the salticid Habronattus pyrrithrix. Behavioral work indicates that this animal is sensitive to color stimuli ranging from UV to red. Our data reveal that these animals use a combination of spectral sensitivities and pre- and intra-retinal filtering to achieve this broad range of color sensitivity. The presented physiological groundwork lays the foundation for future comparative studies of vision and visual signals throughout Habronattus and other salticid genera.
Koyanagi M*: Wavelength sensitivity and depth perception mechanism in a jumping spider.
A wide variety of animals receive environmental light information with eyes and use the information for varied visual tasks. In eyes, retinal-based photopigment rhodopsin, also called visual pigment, captures light in visual photoreceptor cells and starts the visual signaling. Because the spectral sensitivities of visual pigments are adaptively tuned to optimize informational capacity in most visual systems, elucidation of the spectral sensitivities provides a cue to the characteristics of the vision. Recently, we have investigated the molecular basis of the well-developed vision in a jumping spider. Interestingly, the principal eye of jumping spiders has been known to have a unique retina with four tiered photoreceptor layers, on each of which light of different wavelengths is focused due to chromatic aberration of the lens. We found that green-sensitive visual pigments are localized in the two deepest layers (Layers I and II) and that UV-sensitive pigments are localized in the two shallowest layers (Layers III and IV). For Layers I, III and IV, the spectral sensitivity of the visual pigment fits the wavelength of light that were previously found to be focused on that layer, which enables to capture focused images of both green and UV lights. Unexpectedly, this was not the case for Layer II, suggesting that Layer II receives defocused images, which contain depth information of the scene in optical theory. Behavioral experiments under the light which affects the amount of defocus in the images strongly suggest that jumping spiders perceive depth using image defocus.
Osaka City University, Department of Biology and Geosciences, Graduate School of Science; [email protected]; ISBE2014 Symposium Talk.
Wilts BD*, Stavenga DG: Living in a digital world: butterfly wing coloration and its connection to vision.
The biological world has exploited photonic structures since the Cambrian explosion over 500 million years ago, with which an enormous diversification of insect coloration as well as visual systems started. The (co-)evolution of prey and predators has since led to the amazing diversity of coloration mechanisms that reflect bright colors but also to optimization of visual systems to detect specific light compositions. Butterfly wing displays feature intricate optical structures that have evolved to reflect light in a specialist way. Organismal colors can be due to structural arrangements on the mesoscale (structural colors) or/and due to pigments absorbing in a restricted wavelength range (pigmentary colors). Insect displays often fulfill specific biological functions with the most obvious function being social and intraspecific signaling, as e.g. by the vivid colored pierid and birdwing butterflies. More specialized functions are aposematic signaling, as seen in the Emerald-Cattleheart butterfly, Parides sesostris, or camouflage in foliaceous environments (Green Hairstreak, Callophrys rubi). We have characterized the photonic structures found in several insects and will discuss their spatial and spectral optical properties.Surprisingly, most wing colors appear to be digital, e.g. strong (similar) colors covering step-like areas in a restricted wavelength range. Blue/green/yellow colors appear universally, while others are hardly observed. This could suggest a tuning of insect displays to the visual system and we will tentatively conclude that by comparing the spectral properties of the displays with the spectral sensitivities of the insects' photoreceptors. From this dataset, we suggest that insect displays are tuned to their visual systems.
University of Cambridge, Cavendish Laboratories, Department of Physics; [email protected]; ISBE2014 Symposium Talk
Li D*, Chen ZQ, Xu X, Zhang ZT: UV coloration in jumping spiders: mechanisms, function and evolution.
Many animals have body parts that reflect ultraviolet (UV: < 400 nm) light. In species that exhibit sexual dimorphism, UV-reflecting ornaments are commonly involved in intra-specific interactions. Therefore, it is often suggested that the evolution of these traits might be the consequence of sexual selection. Over the past two decades, it has been well established that male UV-A (320-400 nm) ornamentation falls under direct selection through female preferences in many animals, including birds, fishes, reptiles, insects, and spiders. However, the adaptive significance of UV-B (280-320 nm) coloration, the relative importance of UV-A and UV-B in sexual selection as well as the origin and evolution of UV-based mate preferences are still poorly understood. In this talk, I will first provide a brief review on UV vision, UV coloration and the perception of UV coloration in jumping spiders (Araneae: Salticidae). I will then highlight our recent studies on the role of UV-A and UV-B in female mate choice and the relative importance of UV-A and UV-B in sexual selection in salticids. Next, I will present our data on how UV-based female choice occurred at first place and evolved in jumping spiders. Furthermore, I will provide some data on the mechanisms of UV color production. Finally, I will discuss about likely future studies of UV coloration in salticids in particular and in animals in general.
National University of Singapore; Hubei University, Department of Biological Sciences; Centre for Behavioural Ecology & Evolution, College of Life Sciences; [email protected]; ISBE2014 Symposium Talk.
Henze MJ*, Lind O, Kohler M, Kelber A: Seeing and (not) being seen:The sensory basis of color signals in a polymorphic damselfly.
Adult blue-tailed damselflies (Ischnura elegans) are color-polymorphic insects. Males turn bright green after emergence and become blue over the days. Females show a red or purple coloration first and, when sexually mature, either mimic the blue color of the males or are camouflaged by an inconspicuous olive-green or brown. Even though I. elegans has been studied intensely, the sensory basis of the color signals for intraspecific and predator-prey interactions has never been explored. We quantified backgrounds in the natural habitat and the body coloration of the damselflies by spectral reflectance measurements, including time series documenting the animals' color change. To understand the function of the colors for mate and rival detection, we determined the angular, spectral and polarization sensitivity of photoreceptors in the compound eyes of males. Four spectral types of receptors maximally sensitive in the UV, blue, green and red region of the spectrum were found by intracellular recordings. Combining spectral reflectance and spectral sensitivity data in a model enabled us to reconstruct the saliency of the different color morphs to conspecific males searching for mates or trying to chase off rivals. The functions of the colors for predator avoidance are also largely unknown. In a similar model, we therefore incorporated known spectral sensitivities of passerines, potential predators on I. elegans. This allows us to judge which color morphs are best camouflaged for the birds. Our goal is a physiologically based understanding of the reasons for color polymorphism, a common phenomenon - not only in damselflies.
Lund University, Department of Biology Vision Group; [email protected]; ISBE2014 Symposium Talk.
Scales JA, Schoroeder R, Rivera JA, Linkem CN, Butler MA*: Color signaling and behavioral modification in an adaptive radiation of Hawaiian damselflies.
Color cues play an important role in the detection of prey items and in communication, especially with respect to mating. However, sending and receiving color signals can be complex as most light environments, like that of forests, are heterogeneous. The forest canopy filters light, and objects in the habitat reflect light differently so that patches of light can vary in color and intensity. Thus, we may expect species living in such variable light habitats to take advantage of micro-site heterogeneity tobehaviorally maximize their color signal efficacy. Megalagrion damselflies utilize a diversity of breeding microhabitats that vary in light quality, are territorial spending much of their time perched observing the environment, and are brilliantly colored, with extensive variation both across species and sexes. Moreover, many species live sympatrically in multi-species communities. Here, we examine the role of coloration in Hawaiian damselflies in guiding behavior, the role of environmental heterogeneity in communication, and specifically whether individuals use perch position to improve the effectiveness of their visual signals or reception of visual information. Field behavioral tests demonstrated that different colors elicit distinct behavioral responses from male damselflies, which vary across species. Furthermore, we show that damselflies can perch to not only maximize their own visibility, but also to improve the contrast of conspecifics within their habitat. These views importantly improved the detection of conspecifics, but not potential prey items, providing evidence that these damselflies use behavior to improve their color signaling for sexual communication, and not simply a general improvement of vision.
University of Hawaii, Manoa, Department of Biology; [email protected]; ISBE2014 Symposium Talk.
Limeri LB*, Morehouse NI: Sensory limitations and the maintenance of color polymorphisms: Female color polymorphisms through male eyes.
Although color polymorphisms are a widespread and conspicuous component of biodiversity, the selective pressures that act to maintain multiple morphs within populations remain poorly understood in most cases. In particular, the role that visual system limitations may play in maintaining multiple color morphs is not well explored. We used a female-limited color polymorphism common to the butterfly genus Colias, called the ‘alba’ polymorphism, to investigate the hypotheses that mate-searching males may struggle to discriminate pale ‘alba’ females from co-occurring heterospecific white butterflies, or that ‘alba’ females may be more difficult to detect than non-‘alba’ females in natural scenes. Such perceptual limitations may influence the relative mating rates of ‘alba’ versus non-‘alba’ females, contributing to the evolutionary persistence of both morphs. Based on receptor-noise-limited modeling of the male Colias visual system, we estimate that when viewed side-by-side, male Colias should be able to discriminate ‘alba’ females from other co-occurring heterospecific butterflies. However, under field conditions that involve larger distances in space or time, males are likely to face challenges discriminating between conspecific ‘alba’ females and co-occurring heterospecific white butterflies, particularly heterospecific ‘alba’ females. We find mixed support for the hypothesis that the two female morphs differ in their salience against the natural background. Our results suggest that constraints arising from male visual function may be involved in the maintenance of this color polymorphism. We argue that such visual system constraints may play a larger role in the maintenance of color polymorphism than has been empirically appreciated to date.
University of Pittsburgh, Department of Biological Sciences; [email protected]; ISBE2014 Symposium Talk.
Schultz TD*, Marley M: Structural colors provide a flexible mechanism for evolving alternative forms of camouflage in different habitats.
Camouflage defense strategies are widely employed by diurnal insects and include background matching, masquerade, and disruptive coloration. The effectiveness of these different options depend on predator vision and the structure of the visual background, but may be further constrained by behavioral and thermoregulatory requirements of the prey. Most tiger beetles are highly active ectothermic predators on open soil and are necessarily exposed to avian predators. Some species exhibit extraordinary geographic variation in dorsal coloration due to minor switches in the deposition of melanin within the cuticle. Slight changes in the thickness of thin epicuticular layers produce interference colors that match any background. Structural white markings that may provide disruptive coloration or affect the grain of the dorsal color pattern are produced by the suppression of melanin in the wing covers. Using spectrometry, image analysis, and a physiological model of avian vision, we assessed the conspicuousness of different tiger beetle populations on their respective backgrounds. Dorsal colorations matched the local soils below the level of detectability and white markings broke up the outline of beetles on fine-grained substrates. However, on light soils where maintaining a high body temperature required frequent basking, beetles masqueraded as dark objects, usually stones, with reduced white markings that conformed to the size and shape of the objects. The combination of interference colors and structural white bands make it possible for tiger beetle populations to adapt to local backgrounds and shift defense strategies when under thermal constraints.
Denison University, Department of Biology; [email protected]; ISBE2014 Symposium Talk.
Kemp DJ, Herberstein ME*, Fleishman L, Whiting MJ: A conceptual framework for the study of coloration in nature.
The world in color presents a dazzling dimension of phenotypic variation. Interest in studying color traits is burgeoning due to the increased accessibility of spectrometers coupled with heightened appreciation of how animals view color very differently to humans. However, accurate, biologically-relevant appraisals of color are challenged by the complexities of reconstructing how spectral information is perceived, integrated and processed in the brains of viewers. We therefore consider that color research requires a marriage between two schools of enquiry, termed top-down and bottom-up approaches. Top-down studies are broadly motivated to use color traits to examine ecological and/or evolutionary processes, and are often performed by non-color specialists using novel species. Bottom-up enquiry, on the other hand, seeks to understand the visual and perceptual basis of color signal reception, and targets few increasingly well-characterized model systems. Reconciling these two schools is critical, not in the least because bottom-up insights generate the intellectual and analytic principles for top-down studies, which in turn may validate such principles. In this paper we present a conceptual framework for color research that emphasizes the need for unification and reciprocity among these parallel schools of enquiry.
Macquarie University, Department of Biological Sciences; [email protected]; ISBE2014 Symposium Talk.
Taylor LA*, Maier E, Byrne K, Amin Z, Morehouse NI: Color in the undergrowth: flexible color biases and learning in foraging jumping spiders.
Understanding the design of prey defenses, such as aposematic colors, involves understanding the perceptual and cognitive abilities of predators that drive their evolution. Research in this area has focused on ‘key’ predators (e.g., birds), with less attention to invertebrate predators. To understand selection pressures that jumping spiders exert on prey color patterns, we first examined natural biases by offering field-collected Habronattus pyrrithrix arrays of artificially colored crickets. We found population-wide color biases with the lowest attack rates on red and yellow prey (colors commonly used as warning colors) and highest attack rates on blue. We then examined whether we could ‘train’ naïve spiders to develop color biases by manipulating their exposure to naturally-occurring prey. Spiders were randomly assigned to one of three diet treatments: (1) white-eyed Drosophila and distasteful red milkweed bugs (fed milkweed seeds), (2) white-eyed Drosophila and palatable red milkweed bugs (fed sunflower seeds), or (3) white-eyed Drosophila only (control). When tested with artificially colored crickets, we found that spiders in Group 1 demonstrated an aversion to red, spiders in Group 2 demonstrated a preference for red, and spiders in Group 3 showed no color bias. We discuss the implications of such biases and learning for the evolution of prey coloration. Moreover, many of the colors that females avoid when foraging are the same colors that males incorporate into their colorful courtship displays; we will discuss ongoing work examining potential spillover between a female’s learned food color biases and her responses to the same colors in male courtship.
University of Florida, Florida Museum of Natural History; [email protected]; ISBE2014 Symposium Talk.
Papaj DR*: Multiple signals for multiple outcomes: How bumblebees manage visually-based floral signals in multiple reward contexts.
Animals in their daily lives must respond effectively to numerous distinct signals in diverse contexts. How animals manage multiple signal use in cognitive terms is not well understood. We are endeavoring to understand the use of visually-based floral signals by bumble bees foraging for multiple types of floral rewards. For many invertebrate pollinator species, pollen and floral nectar constitute important and complementary nutrient sources. Pollen is often offered as a floral reward and is sometimes even the only reward. Yet most studies of pollinator behavior to date have focused nearly exclusively on floral signals in relation to nectar collection. In this talk, we outline key considerations in how members of a bee colony manage use of multiple floral color signals in the context of collection of pollen and nectar. We present evidence that learning plays an important role in the use of color signals in pollen collection and discuss how visual learning in relation to nectar collection may interact with visual learning in relation to pollen collection. Finally, we discuss how the signal sender, i.e., the flower, may exploit color sensitivities specific to one reward type or the other, so as to direct pollinators to the reward for which they are motivated to forage.
University of Arizona, Department of Ecology and Evolutionary Biology; [email protected]; ISBE2014 Symposium Talk.
Jones PL*, Ryan MJ, Chittka L: Interactions between innate color preferences, individual experience and social information in bumblebee foraging decisions.
Animals forage in complex habitats where they must make decisions about which resources to consume and which to ignore. Foraging decisions can be influenced by many factors including innate preferences, individual experiences, and social information. We examined how these factors interact to affect which colored flowers bumblebees, Bombus terrestris audax, select to approach. Naïve bees were first tested for their innate preferences for blue and yellow artificial flowers. Bees were then given individual experience foraging on flowers of an assigned color that was associated with either high quality rewards or low quality rewards. In the next step bees were presented with social information about flowers of the alternate color. When bees had no individual experience they were attracted to flower colors about which they had social information; but this preference was only significant when the socially demonstrated flower was the color for which bees had an innate preference. When bees had individual experience foraging on a color with high quality rewards they ignored social information about other colors regardless of innate color preferences. In contrast, when bees had individual experience foraging on colored flowers with poor quality rewards, they were more likely to use social information to learn to approach alternate colors but only when the alternate color was innately preferred. This is one of the few studies to examine social learning strategies in bumblebees, and is unique in its investigation of the interactions between innate preferences, individual experience and social learning in animal decision-making.
University of Texas at Austin; [email protected]; ISBE2014 Symposium Talk.
Girard MB*, Rosenblum EB, Kasumovic MM: Sexual selection and signal evolution: diversification of peacock spiders (genus: Maratus).
Australian endemic jumping spiders of the Maratus genus use visual displays in conjunction with vibratory signals during courtship. This group exhibits some of the most elaborate animal displays known and preliminary data suggests over forty different species that vary widely in both visual and vibrational signaling traits, as well as habitat type. Accordingly, these spiders provide an excellent opportunity to study sexual selection, multi-modal communication and trends in diversification. In order to elucidate patterns of complex signal use in peacock spiders, we characterized male visual (morphological and behavioral) and vibrational signal diversity for over twenty-five distinct Maratus species, as well as several outgroups. Using these specimens, which were collected from a diverse range of habitats across Australia, we constructed a molecular phylogeny for the genus. We determined relationships between different species, and thus were able to test evolutionary hypotheses about complex signal evolution. Overall, this study provides the first comparative look at signaling behavior and sexual selection in Maratus peacock spiders.
University of California, Berkeley, University of New South Wales, Environmental Science, Policy and Management Department, Division: Organisms and the Environment; [email protected]; ISBE2014 Symposium Talk.
Limeri LB*, Morehouse NI: Sensory limitations and the maintenance of color polymorphisms: Female color polymorphisms through male eyes.
Although color polymorphisms are a widespread and conspicuous component of biodiversity, the selective pressures that act to maintain multiple morphs within populations remain poorly understood in most cases. In particular, the role that visual system limitations may play in maintaining multiple color morphs is not well explored. We used a female-limited color polymorphism common to the butterfly genus Colias, called the ‘alba’ polymorphism, to investigate the hypotheses that mate-searching males may struggle to discriminate pale ‘alba’ females from co-occurring heterospecific white butterflies, or that ‘alba’ females may be more difficult to detect than non-‘alba’ females in natural scenes. Such perceptual limitations may influence the relative mating rates of ‘alba’ versus non-‘alba’ females, contributing to the evolutionary persistence of both morphs. Based on receptor-noise-limited modeling of the male Colias visual system, we estimate that when viewed side-by-side, male Colias should be able to discriminate ‘alba’ females from other co-occurring heterospecific butterflies. However, under field conditions that involve larger distances in space or time, males are likely to face challenges discriminating between conspecific ‘alba’ females and co-occurring heterospecific white butterflies, particularly heterospecific ‘alba’ females. We find mixed support for the hypothesis that the two female morphs differ in their salience against the natural background. Our results suggest that constraints arising from male visual function may be involved in the maintenance of this color polymorphism. We argue that such visual system constraints may play a larger role in the maintenance of color polymorphism than has been empirically appreciated to date.
University of Pittsburgh, Department of Biological Sciences; [email protected]; ISBE2014 Symposium Talk.
The spider family Salticidae (Jumping spiders) offers immense potential for the study of visually guided behavior and visual signal evolution due to their complex visual systems, sophisticated behavioral repertoires, and high ecological and species diversity. Behavioral evidence suggests that color plays a major role in the lives of these animals, including the identification of suitable prey and the selection of attractive mates. However, a number of key questions remain regarding how this group of animals sees color. Previous work has established that color vision is enabled by the large forward-facing principal eyes, but comprehensive characterization of visual sensitivities has proved challenging to access using traditional methods. The small number of available studies hints at considerable species diversity in wavelength sensitivities. By using an MSP-based approach, a first in arachnids, we characterized spectral transmission profiles of photoreceptors, as well as of pre-retinal optical elements in the principal eyes of the salticid Habronattus pyrrithrix. Behavioral work indicates that this animal is sensitive to color stimuli ranging from UV to red. Our data reveal that these animals use a combination of spectral sensitivities and pre- and intra-retinal filtering to achieve this broad range of color sensitivity. The presented physiological groundwork lays the foundation for future comparative studies of vision and visual signals throughout Habronattus and other salticid genera.
Koyanagi M*: Wavelength sensitivity and depth perception mechanism in a jumping spider.
A wide variety of animals receive environmental light information with eyes and use the information for varied visual tasks. In eyes, retinal-based photopigment rhodopsin, also called visual pigment, captures light in visual photoreceptor cells and starts the visual signaling. Because the spectral sensitivities of visual pigments are adaptively tuned to optimize informational capacity in most visual systems, elucidation of the spectral sensitivities provides a cue to the characteristics of the vision. Recently, we have investigated the molecular basis of the well-developed vision in a jumping spider. Interestingly, the principal eye of jumping spiders has been known to have a unique retina with four tiered photoreceptor layers, on each of which light of different wavelengths is focused due to chromatic aberration of the lens. We found that green-sensitive visual pigments are localized in the two deepest layers (Layers I and II) and that UV-sensitive pigments are localized in the two shallowest layers (Layers III and IV). For Layers I, III and IV, the spectral sensitivity of the visual pigment fits the wavelength of light that were previously found to be focused on that layer, which enables to capture focused images of both green and UV lights. Unexpectedly, this was not the case for Layer II, suggesting that Layer II receives defocused images, which contain depth information of the scene in optical theory. Behavioral experiments under the light which affects the amount of defocus in the images strongly suggest that jumping spiders perceive depth using image defocus.
Osaka City University, Department of Biology and Geosciences, Graduate School of Science; [email protected]; ISBE2014 Symposium Talk.
Wilts BD*, Stavenga DG: Living in a digital world: butterfly wing coloration and its connection to vision.
The biological world has exploited photonic structures since the Cambrian explosion over 500 million years ago, with which an enormous diversification of insect coloration as well as visual systems started. The (co-)evolution of prey and predators has since led to the amazing diversity of coloration mechanisms that reflect bright colors but also to optimization of visual systems to detect specific light compositions. Butterfly wing displays feature intricate optical structures that have evolved to reflect light in a specialist way. Organismal colors can be due to structural arrangements on the mesoscale (structural colors) or/and due to pigments absorbing in a restricted wavelength range (pigmentary colors). Insect displays often fulfill specific biological functions with the most obvious function being social and intraspecific signaling, as e.g. by the vivid colored pierid and birdwing butterflies. More specialized functions are aposematic signaling, as seen in the Emerald-Cattleheart butterfly, Parides sesostris, or camouflage in foliaceous environments (Green Hairstreak, Callophrys rubi). We have characterized the photonic structures found in several insects and will discuss their spatial and spectral optical properties.Surprisingly, most wing colors appear to be digital, e.g. strong (similar) colors covering step-like areas in a restricted wavelength range. Blue/green/yellow colors appear universally, while others are hardly observed. This could suggest a tuning of insect displays to the visual system and we will tentatively conclude that by comparing the spectral properties of the displays with the spectral sensitivities of the insects' photoreceptors. From this dataset, we suggest that insect displays are tuned to their visual systems.
University of Cambridge, Cavendish Laboratories, Department of Physics; [email protected]; ISBE2014 Symposium Talk
Li D*, Chen ZQ, Xu X, Zhang ZT: UV coloration in jumping spiders: mechanisms, function and evolution.
Many animals have body parts that reflect ultraviolet (UV: < 400 nm) light. In species that exhibit sexual dimorphism, UV-reflecting ornaments are commonly involved in intra-specific interactions. Therefore, it is often suggested that the evolution of these traits might be the consequence of sexual selection. Over the past two decades, it has been well established that male UV-A (320-400 nm) ornamentation falls under direct selection through female preferences in many animals, including birds, fishes, reptiles, insects, and spiders. However, the adaptive significance of UV-B (280-320 nm) coloration, the relative importance of UV-A and UV-B in sexual selection as well as the origin and evolution of UV-based mate preferences are still poorly understood. In this talk, I will first provide a brief review on UV vision, UV coloration and the perception of UV coloration in jumping spiders (Araneae: Salticidae). I will then highlight our recent studies on the role of UV-A and UV-B in female mate choice and the relative importance of UV-A and UV-B in sexual selection in salticids. Next, I will present our data on how UV-based female choice occurred at first place and evolved in jumping spiders. Furthermore, I will provide some data on the mechanisms of UV color production. Finally, I will discuss about likely future studies of UV coloration in salticids in particular and in animals in general.
National University of Singapore; Hubei University, Department of Biological Sciences; Centre for Behavioural Ecology & Evolution, College of Life Sciences; [email protected]; ISBE2014 Symposium Talk.
Henze MJ*, Lind O, Kohler M, Kelber A: Seeing and (not) being seen:The sensory basis of color signals in a polymorphic damselfly.
Adult blue-tailed damselflies (Ischnura elegans) are color-polymorphic insects. Males turn bright green after emergence and become blue over the days. Females show a red or purple coloration first and, when sexually mature, either mimic the blue color of the males or are camouflaged by an inconspicuous olive-green or brown. Even though I. elegans has been studied intensely, the sensory basis of the color signals for intraspecific and predator-prey interactions has never been explored. We quantified backgrounds in the natural habitat and the body coloration of the damselflies by spectral reflectance measurements, including time series documenting the animals' color change. To understand the function of the colors for mate and rival detection, we determined the angular, spectral and polarization sensitivity of photoreceptors in the compound eyes of males. Four spectral types of receptors maximally sensitive in the UV, blue, green and red region of the spectrum were found by intracellular recordings. Combining spectral reflectance and spectral sensitivity data in a model enabled us to reconstruct the saliency of the different color morphs to conspecific males searching for mates or trying to chase off rivals. The functions of the colors for predator avoidance are also largely unknown. In a similar model, we therefore incorporated known spectral sensitivities of passerines, potential predators on I. elegans. This allows us to judge which color morphs are best camouflaged for the birds. Our goal is a physiologically based understanding of the reasons for color polymorphism, a common phenomenon - not only in damselflies.
Lund University, Department of Biology Vision Group; [email protected]; ISBE2014 Symposium Talk.
Scales JA, Schoroeder R, Rivera JA, Linkem CN, Butler MA*: Color signaling and behavioral modification in an adaptive radiation of Hawaiian damselflies.
Color cues play an important role in the detection of prey items and in communication, especially with respect to mating. However, sending and receiving color signals can be complex as most light environments, like that of forests, are heterogeneous. The forest canopy filters light, and objects in the habitat reflect light differently so that patches of light can vary in color and intensity. Thus, we may expect species living in such variable light habitats to take advantage of micro-site heterogeneity tobehaviorally maximize their color signal efficacy. Megalagrion damselflies utilize a diversity of breeding microhabitats that vary in light quality, are territorial spending much of their time perched observing the environment, and are brilliantly colored, with extensive variation both across species and sexes. Moreover, many species live sympatrically in multi-species communities. Here, we examine the role of coloration in Hawaiian damselflies in guiding behavior, the role of environmental heterogeneity in communication, and specifically whether individuals use perch position to improve the effectiveness of their visual signals or reception of visual information. Field behavioral tests demonstrated that different colors elicit distinct behavioral responses from male damselflies, which vary across species. Furthermore, we show that damselflies can perch to not only maximize their own visibility, but also to improve the contrast of conspecifics within their habitat. These views importantly improved the detection of conspecifics, but not potential prey items, providing evidence that these damselflies use behavior to improve their color signaling for sexual communication, and not simply a general improvement of vision.
University of Hawaii, Manoa, Department of Biology; [email protected]; ISBE2014 Symposium Talk.
Limeri LB*, Morehouse NI: Sensory limitations and the maintenance of color polymorphisms: Female color polymorphisms through male eyes.
Although color polymorphisms are a widespread and conspicuous component of biodiversity, the selective pressures that act to maintain multiple morphs within populations remain poorly understood in most cases. In particular, the role that visual system limitations may play in maintaining multiple color morphs is not well explored. We used a female-limited color polymorphism common to the butterfly genus Colias, called the ‘alba’ polymorphism, to investigate the hypotheses that mate-searching males may struggle to discriminate pale ‘alba’ females from co-occurring heterospecific white butterflies, or that ‘alba’ females may be more difficult to detect than non-‘alba’ females in natural scenes. Such perceptual limitations may influence the relative mating rates of ‘alba’ versus non-‘alba’ females, contributing to the evolutionary persistence of both morphs. Based on receptor-noise-limited modeling of the male Colias visual system, we estimate that when viewed side-by-side, male Colias should be able to discriminate ‘alba’ females from other co-occurring heterospecific butterflies. However, under field conditions that involve larger distances in space or time, males are likely to face challenges discriminating between conspecific ‘alba’ females and co-occurring heterospecific white butterflies, particularly heterospecific ‘alba’ females. We find mixed support for the hypothesis that the two female morphs differ in their salience against the natural background. Our results suggest that constraints arising from male visual function may be involved in the maintenance of this color polymorphism. We argue that such visual system constraints may play a larger role in the maintenance of color polymorphism than has been empirically appreciated to date.
University of Pittsburgh, Department of Biological Sciences; [email protected]; ISBE2014 Symposium Talk.
Schultz TD*, Marley M: Structural colors provide a flexible mechanism for evolving alternative forms of camouflage in different habitats.
Camouflage defense strategies are widely employed by diurnal insects and include background matching, masquerade, and disruptive coloration. The effectiveness of these different options depend on predator vision and the structure of the visual background, but may be further constrained by behavioral and thermoregulatory requirements of the prey. Most tiger beetles are highly active ectothermic predators on open soil and are necessarily exposed to avian predators. Some species exhibit extraordinary geographic variation in dorsal coloration due to minor switches in the deposition of melanin within the cuticle. Slight changes in the thickness of thin epicuticular layers produce interference colors that match any background. Structural white markings that may provide disruptive coloration or affect the grain of the dorsal color pattern are produced by the suppression of melanin in the wing covers. Using spectrometry, image analysis, and a physiological model of avian vision, we assessed the conspicuousness of different tiger beetle populations on their respective backgrounds. Dorsal colorations matched the local soils below the level of detectability and white markings broke up the outline of beetles on fine-grained substrates. However, on light soils where maintaining a high body temperature required frequent basking, beetles masqueraded as dark objects, usually stones, with reduced white markings that conformed to the size and shape of the objects. The combination of interference colors and structural white bands make it possible for tiger beetle populations to adapt to local backgrounds and shift defense strategies when under thermal constraints.
Denison University, Department of Biology; [email protected]; ISBE2014 Symposium Talk.
Kemp DJ, Herberstein ME*, Fleishman L, Whiting MJ: A conceptual framework for the study of coloration in nature.
The world in color presents a dazzling dimension of phenotypic variation. Interest in studying color traits is burgeoning due to the increased accessibility of spectrometers coupled with heightened appreciation of how animals view color very differently to humans. However, accurate, biologically-relevant appraisals of color are challenged by the complexities of reconstructing how spectral information is perceived, integrated and processed in the brains of viewers. We therefore consider that color research requires a marriage between two schools of enquiry, termed top-down and bottom-up approaches. Top-down studies are broadly motivated to use color traits to examine ecological and/or evolutionary processes, and are often performed by non-color specialists using novel species. Bottom-up enquiry, on the other hand, seeks to understand the visual and perceptual basis of color signal reception, and targets few increasingly well-characterized model systems. Reconciling these two schools is critical, not in the least because bottom-up insights generate the intellectual and analytic principles for top-down studies, which in turn may validate such principles. In this paper we present a conceptual framework for color research that emphasizes the need for unification and reciprocity among these parallel schools of enquiry.
Macquarie University, Department of Biological Sciences; [email protected]; ISBE2014 Symposium Talk.
Taylor LA*, Maier E, Byrne K, Amin Z, Morehouse NI: Color in the undergrowth: flexible color biases and learning in foraging jumping spiders.
Understanding the design of prey defenses, such as aposematic colors, involves understanding the perceptual and cognitive abilities of predators that drive their evolution. Research in this area has focused on ‘key’ predators (e.g., birds), with less attention to invertebrate predators. To understand selection pressures that jumping spiders exert on prey color patterns, we first examined natural biases by offering field-collected Habronattus pyrrithrix arrays of artificially colored crickets. We found population-wide color biases with the lowest attack rates on red and yellow prey (colors commonly used as warning colors) and highest attack rates on blue. We then examined whether we could ‘train’ naïve spiders to develop color biases by manipulating their exposure to naturally-occurring prey. Spiders were randomly assigned to one of three diet treatments: (1) white-eyed Drosophila and distasteful red milkweed bugs (fed milkweed seeds), (2) white-eyed Drosophila and palatable red milkweed bugs (fed sunflower seeds), or (3) white-eyed Drosophila only (control). When tested with artificially colored crickets, we found that spiders in Group 1 demonstrated an aversion to red, spiders in Group 2 demonstrated a preference for red, and spiders in Group 3 showed no color bias. We discuss the implications of such biases and learning for the evolution of prey coloration. Moreover, many of the colors that females avoid when foraging are the same colors that males incorporate into their colorful courtship displays; we will discuss ongoing work examining potential spillover between a female’s learned food color biases and her responses to the same colors in male courtship.
University of Florida, Florida Museum of Natural History; [email protected]; ISBE2014 Symposium Talk.
Papaj DR*: Multiple signals for multiple outcomes: How bumblebees manage visually-based floral signals in multiple reward contexts.
Animals in their daily lives must respond effectively to numerous distinct signals in diverse contexts. How animals manage multiple signal use in cognitive terms is not well understood. We are endeavoring to understand the use of visually-based floral signals by bumble bees foraging for multiple types of floral rewards. For many invertebrate pollinator species, pollen and floral nectar constitute important and complementary nutrient sources. Pollen is often offered as a floral reward and is sometimes even the only reward. Yet most studies of pollinator behavior to date have focused nearly exclusively on floral signals in relation to nectar collection. In this talk, we outline key considerations in how members of a bee colony manage use of multiple floral color signals in the context of collection of pollen and nectar. We present evidence that learning plays an important role in the use of color signals in pollen collection and discuss how visual learning in relation to nectar collection may interact with visual learning in relation to pollen collection. Finally, we discuss how the signal sender, i.e., the flower, may exploit color sensitivities specific to one reward type or the other, so as to direct pollinators to the reward for which they are motivated to forage.
University of Arizona, Department of Ecology and Evolutionary Biology; [email protected]; ISBE2014 Symposium Talk.
Jones PL*, Ryan MJ, Chittka L: Interactions between innate color preferences, individual experience and social information in bumblebee foraging decisions.
Animals forage in complex habitats where they must make decisions about which resources to consume and which to ignore. Foraging decisions can be influenced by many factors including innate preferences, individual experiences, and social information. We examined how these factors interact to affect which colored flowers bumblebees, Bombus terrestris audax, select to approach. Naïve bees were first tested for their innate preferences for blue and yellow artificial flowers. Bees were then given individual experience foraging on flowers of an assigned color that was associated with either high quality rewards or low quality rewards. In the next step bees were presented with social information about flowers of the alternate color. When bees had no individual experience they were attracted to flower colors about which they had social information; but this preference was only significant when the socially demonstrated flower was the color for which bees had an innate preference. When bees had individual experience foraging on a color with high quality rewards they ignored social information about other colors regardless of innate color preferences. In contrast, when bees had individual experience foraging on colored flowers with poor quality rewards, they were more likely to use social information to learn to approach alternate colors but only when the alternate color was innately preferred. This is one of the few studies to examine social learning strategies in bumblebees, and is unique in its investigation of the interactions between innate preferences, individual experience and social learning in animal decision-making.
University of Texas at Austin; [email protected]; ISBE2014 Symposium Talk.
Girard MB*, Rosenblum EB, Kasumovic MM: Sexual selection and signal evolution: diversification of peacock spiders (genus: Maratus).
Australian endemic jumping spiders of the Maratus genus use visual displays in conjunction with vibratory signals during courtship. This group exhibits some of the most elaborate animal displays known and preliminary data suggests over forty different species that vary widely in both visual and vibrational signaling traits, as well as habitat type. Accordingly, these spiders provide an excellent opportunity to study sexual selection, multi-modal communication and trends in diversification. In order to elucidate patterns of complex signal use in peacock spiders, we characterized male visual (morphological and behavioral) and vibrational signal diversity for over twenty-five distinct Maratus species, as well as several outgroups. Using these specimens, which were collected from a diverse range of habitats across Australia, we constructed a molecular phylogeny for the genus. We determined relationships between different species, and thus were able to test evolutionary hypotheses about complex signal evolution. Overall, this study provides the first comparative look at signaling behavior and sexual selection in Maratus peacock spiders.
University of California, Berkeley, University of New South Wales, Environmental Science, Policy and Management Department, Division: Organisms and the Environment; [email protected]; ISBE2014 Symposium Talk.
Limeri LB*, Morehouse NI: Sensory limitations and the maintenance of color polymorphisms: Female color polymorphisms through male eyes.
Although color polymorphisms are a widespread and conspicuous component of biodiversity, the selective pressures that act to maintain multiple morphs within populations remain poorly understood in most cases. In particular, the role that visual system limitations may play in maintaining multiple color morphs is not well explored. We used a female-limited color polymorphism common to the butterfly genus Colias, called the ‘alba’ polymorphism, to investigate the hypotheses that mate-searching males may struggle to discriminate pale ‘alba’ females from co-occurring heterospecific white butterflies, or that ‘alba’ females may be more difficult to detect than non-‘alba’ females in natural scenes. Such perceptual limitations may influence the relative mating rates of ‘alba’ versus non-‘alba’ females, contributing to the evolutionary persistence of both morphs. Based on receptor-noise-limited modeling of the male Colias visual system, we estimate that when viewed side-by-side, male Colias should be able to discriminate ‘alba’ females from other co-occurring heterospecific butterflies. However, under field conditions that involve larger distances in space or time, males are likely to face challenges discriminating between conspecific ‘alba’ females and co-occurring heterospecific white butterflies, particularly heterospecific ‘alba’ females. We find mixed support for the hypothesis that the two female morphs differ in their salience against the natural background. Our results suggest that constraints arising from male visual function may be involved in the maintenance of this color polymorphism. We argue that such visual system constraints may play a larger role in the maintenance of color polymorphism than has been empirically appreciated to date.
University of Pittsburgh, Department of Biological Sciences; [email protected]; ISBE2014 Symposium Talk.
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