ORCID Profile
0000-0002-7557-7627
Current Organisations
James Cook University
,
Deakin University
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Publisher: Elsevier BV
Date: 10-1998
Publisher: Elsevier BV
Date: 12-1995
Publisher: Informa UK Limited
Date: 03-2004
DOI: 10.1071/MU03007
Publisher: Elsevier BV
Date: 1987
DOI: 10.1016/0042-6989(87)90200-8
Abstract: Visual pigment polymorphism similar to that found in primates is described in the photoreceptors of wild-caught guppies (Poecilia reticulata). Microspectrophotometric examination of retinal cells revealed rod visual pigments with a lambda max close to 503 nm. Classes of cones with lambda max around 410 and 465 nm were found, together with a population of pigments in the 529-579 nm range. It is in these long-wavelength cones that polymorphism occurs. Male guppies are highly polymorphic for body colour and it is possible that the cone polymorphism is related to the appreciation of the different yellow, orange and red carotenoid colour spots that are used in sexual display.
Publisher: Wiley
Date: 04-03-2016
DOI: 10.1002/PRO.2902
Publisher: University of Chicago Press
Date: 04-2015
DOI: 10.1086/680010
Abstract: There is no conclusive evidence of any nonhuman animal using the sun as part of its predation strategy. Here, we show that the world's largest predatory fish-the white shark (Carcharodon carcharias)-exploits the sun when approaching baits by positioning the sun directly behind them. On sunny days, sharks reversed their direction of approach along an east-west axis from morning to afternoon but had uniformly distributed approach directions during overcast conditions. These results show that white sharks have sufficient behavioral flexibility to exploit fluctuating environmental features when predating. This sun-tracking predation strategy has a number of potential functional roles, including improvement of prey detection, avoidance of retinal overstimulation, and predator concealment.
Publisher: Cold Spring Harbor Laboratory
Date: 26-09-2018
DOI: 10.1101/427658
Abstract: Biological colouration presents a canvas for the study of ecological and evolutionary processes. Enduring interest in colour-based phenotypes has driven, and been driven by, improved techniques for quantifying colour patterns in ever-more relevant ways, yet the need for flexible, open frameworks for data processing and analysis persists. Here we introduce pavo 2 , the latest iteration of the R package pavo . This release represents the extensive refinement and expansion of existing methods, as well as a suite of new tools for the cohesive analysis of the spectral and (now) spatial structure of colour patterns and perception. At its core, the package retains a broad focus on (a) the organisation and processing of spectral and spatial data, and tools for the alternating (b) visualisation, and (c) analysis of data. Significantly, pavo 2 introduces image-analysis capabilities, providing a cohesive workflow for the comprehensive analysis of colour patterns. We demonstrate the utility of pavo with a brief ex le centred on mimicry in Heliconius butterflies. Drawing on visual modelling, adjacency, and boundary strength analyses, we show that the combined spectral (colour and luminance) and spatial (pattern element distribution and boundary salience) features of putative models and mimics are closely aligned. pavo 2 offers a flexible and reproducible environment for the analysis of colour, with renewed potential to assist researchers in answering fundamental questions in sensory ecology and evolution.
Publisher: The Society for the Study of Evolution
Date: 2001
DOI: 10.1554/0014-3820(2001)055[1002:DAISSA]2.0.CO;2
Abstract: The ornamentation and displays on which sexual attractiveness and thus mating success are based may be complex and comprise several traits. Predicting the outcome of sexual selection on such complex phenotypes requires an understanding of both the direct operation of selection on each trait and the indirect consequences of selection operating directly on genetically correlated traits. Here we report the results of a quantitative genetic analysis of the ornamentation, sexual attractiveness, and mating success of male guppies (Poecilia reticulata). We analyze male ornamentation both from the point of view of single ornamental traits (e.g., the area of each color) and of composite measures of the way the entire pattern is likely to be perceived by females (e.g., the mean and contrast in chroma). We demonstrate that there is substantial additive genetic variation in almost all measures of male ornamentation and that much of this variation may be Y linked. Attractiveness and mating success are positively correlated at the phenotypic and genetic level. Orange area and chroma, the area of a male's tail, and the color contrast of his pattern overall are positively correlated with attractiveness and/or mating success at the phenotypic and genetic levels. Using attractiveness and mating success as measures of fitness, we estimate gradients of linear directional sexual selection operating on each male trait and use equations of multivariate evolutionary change to predict the response of male ornamentation to this sexual selection. From these analyses, we predict that indirect selection may have important effects on the evolution of male guppy color patterns.
Publisher: Oxford University Press (OUP)
Date: 11-2004
Publisher: The Royal Society
Date: 22-05-2017
Abstract: Animal colour patterns are a model system for understanding evolution because they are unusually accessible for study and experimental manipulation. This is possible because their functions are readily identifiable. In this final paper of the symposium we provide a diagram of the processes affecting colour patterns and use this to summarize their functions and put the other papers in a broad context. This allows us to identify significant ‘holes’ in the field that only become obvious when we see the processes affecting colour patterns, and their interactions, as a whole. We make suggestions about new directions of research that will enhance our understanding of both the evolution of colour patterns and visual signalling but also illuminate how the evolution of multiple interacting traits works. This article is part of the themed issue ‘Animal coloration: production, perception, function and application’.
Publisher: Elsevier BV
Date: 04-2012
Publisher: Oxford University Press (OUP)
Date: 07-1984
Publisher: Oxford University Press (OUP)
Date: 22-11-2005
Publisher: Informa UK Limited
Date: 02-10-2014
Publisher: Oxford University Press (OUP)
Date: 12-1992
DOI: 10.2307/2410053
Publisher: Cold Spring Harbor Laboratory
Date: 20-12-2022
DOI: 10.1101/2022.12.20.521213
Abstract: Aposematic signals advertise underlying defences in many species. They should be detectable (highly contrasting against the background) and bold (high internal pattern contrast) to enhance predator recognition, learning and memorisation. However, the signalling function of aposematic colour patterns may be distance-dependent: signals may be undetectable from a distance to reduce costs of increased attacks from naïve predators but bold when viewed up close. To test this hypothesis, we quantified the chromatic and achromatic detectability and boldness of colour patterns in 13 nudibranch species that varied in the strength of their chemical defences, in terms of unpalatability and toxicity, using Quantitative Colour Pattern Analysis (QCPA) and data on the visual perception of a triggerfish ( Rhinecanthus aculeatus ). When viewed from larger distances, there were no differences in detectability and boldness between well-defended and undefended species. However, when viewed at close distances, well-defended species were more detectable and bolder than undefended species. The detectability of defended species decreased more significantly with increased viewing distances compared to boldness but remained relatively consistent over viewing distances for undefended species. We provide evidence for distance-dependent signalling in aposematic nudibranchs and highlight the importance of distinguishing between signal detectability and boldness in studies of aposematism.
Publisher: Wiley
Date: 28-08-2018
Publisher: Springer Science and Business Media LLC
Date: 22-06-2013
Publisher: Wiley
Date: 12-1992
Publisher: The Royal Society
Date: 26-07-2023
Abstract: Aposematic signals visually advertise underlying anti-predatory defences in many species. They should be detectable (e.g. contrasting against the background) and bold (e.g. using internal pattern contrast) to enhance predator recognition, learning and memorization. However, the signalling function of aposematic colour patterns may be distance-dependent: signals may be undetectable from a distance to reduce increased attacks from naïve predators but bold when viewed up close. Using quantitative colour pattern analysis, we quantified the chromatic and achromatic detectability and boldness of colour patterns in 13 nudibranch species with variable strength of chemical defences in terms of unpalatability and toxicity, approximating the visual perception of a triggerfish ( Rhinecanthus aculeatus ) across a predation sequence (detection to subjugation). When viewed from an ecologically relevant distance of 30 cm, there were no differences in detectability and boldness between well-defended and undefended species. However, when viewed at closer distances (less than 30 cm), well-defended species were more detectable and bolder than undefended species. As distance increased, detectability decreased more significantly than boldness for defended species. For undefended species, boldness and detectability remained comparatively consistent, regardless of viewing distance. We provide evidence for distance-dependent signalling in aposematic nudibranchs and highlight the importance of distinguishing signal detectability from boldness in studies of aposematism.
Publisher: Oxford University Press (OUP)
Date: 08-1981
Publisher: University of Chicago Press
Date: 04-2015
DOI: 10.1086/680022
Abstract: Multicomponent signals are made up of interacting elements that generate a functional signaling unit. The interactions between signal components and their effects on in idual fitness are not well understood, and the effect of environment is even less so. It is usually assumed that color patterns appear the same in all light environments and that the effects of each color are additive. Using guppies, Poecilia reticulata, we investigated the effect of water color on the interactions between components of sexually selected male coloration. Through behavioral mate choice trials in four different water colors, we estimated the attractiveness of male color patterns, using multivariate fitness estimates and overall signal contrast. Our results show that females exhibit preferences that favor groups of colors rather than in idual colors independently and that each environment favors different color combinations. We found that these effects are consistent with female guppies selecting entire color patterns on the basis of overall visual contrast. This suggests that both in iduals and populations inhabiting different light environments will be subject to ergent, multivariate selection. Although the appearance of color patterns changes with light environment, achromatic components change little, suggesting that these could function in species recognition or other aspects of communication that must work across environments. Consequently, we predict different phylogenetic patterns between chromatic and achromatic signals within the same clades.
Publisher: Oxford University Press (OUP)
Date: 12-1990
Publisher: Cold Spring Harbor Laboratory
Date: 17-06-2022
DOI: 10.1101/2022.06.16.496397
Abstract: Edge detection is important for object detection and recognition. However, we do not know whether edge statistics predict the detection of prey by non-human predators. Understanding the link between image statistics and animal behaviour is crucial and of increasing importance given the growing availability of image analyses and their application across non-human visual systems. Here, we investigated whether Boundary Strength Analysis (BSA), Local Edge Intensity Analysis (LEIA) and the Gabor Ratio (GabRat) could predict the speed and success with which triggerfish ( Rhinecanthus aculeatus ) detected patterned circular stimuli against a noisy visual background, in both chromatic and achromatic presentations. We found that in idual pattern statistics could only explain up to 2% of the variation in detection time, whereas PCA regression analysis considering all edge statistics simultaneously explained up to 6% of the variation. This suggests that other factors explained more behavioural variation than in idual edge statistics. Furthermore, different statistics significantly correlated with detection speed depending on treatment, viewing distance, and changes in fish response over time, while highlighting the importance of considering spatial acuity and relevant viewing distances in the study of visual signals. Our results demonstrate the need for broad and unbiased approaches for identifying task-specific predictive relationships between pattern statistics and animal behaviour using image statistics capturing different aspects of colour patterns. We require robust statistical approaches to investigate correlations between ecological effect and the ever-increasing dimensionality and size of datasets in the field of visual ecology, rather than pre-emptively narrowing down the choice of image statistics unless warranted by specific hypotheses. Correlations between edge detecting colour pattern statistics and animal behaviour are complex. Specifically, correlations are unlikely to be explained by single image statistics and depend upon observer distance.
Publisher: The Company of Biologists
Date: 04-2022
DOI: 10.1242/JEB.243533
Abstract: Animals use colour vision in a range of behaviours. Visual performance is limited by thresholds, which are set by noise in photoreceptors and subsequent neural processing. The receptor noise limited (RNL) model of colour discrimination is widely used for modelling colour vision and accounts well for experimental data from many species. In one of the most comprehensive tests yet of colour discrimination in a non-human species, we used Ishihara-style stimulus patterns to examine thresholds for 21 directions at five locations in colour space for the fish Rhinecanthus aculeatus. Thresholds matched RNL model predictions most closely for stimuli near the achromatic point, but exceeded predictions (indicating a decline in sensitivity) with distance from this point. Thresholds were also usually higher for saturation than for hue differences. These changes in colour threshold with colour space location and direction may give insight into photoreceptor non-linearities and post-receptoral mechanisms of colour vision in fish. Our results highlight the need for a cautious interpretation of the RNL model – especially for modelling colours that differ from one another in saturation (rather than hue), and for highly saturated colours distant from the achromatic point in colour space.
Publisher: Springer Science and Business Media LLC
Date: 24-08-2000
Publisher: Springer Science and Business Media LLC
Date: 27-01-2017
DOI: 10.1038/SREP41445
Abstract: Variation in wavelength sensitivity among subspecies is unknown among vertebrates. The parrot Platycercus elegans has extreme plumage variation between subspecies ranging from pale yellow to crimson which, with differences in background colour and light environment between subspecies, makes it a good candidate for the evolution of within-species differences in vision. We report differences in visual pigments between populations of P. elegans from two subspecies, providing the first known support for population and subspecies variation in visual pigments within a vertebrate species it is also the first instance of intraspecific variation in rod sensitivity within any vertebrate species. Differences in wavelength sensitivity of rods and cones corresponded to geographic differences in plumage colour. Between study populations, visual pigments varied but not oil droplets. Adaptive functions for the visual pigment differences are untested but they could cause ergence in behaviours associated with colour as well as in dim light, and provide insights into the role of senses in ergence and speciation.
Publisher: The Society for the Study of Evolution
Date: 2001
Publisher: The Royal Society
Date: 23-09-2009
Abstract: Sexual selection is thought to be opposed by natural selection such that ornamental traits express a balance between these two antagonistic influences. Phenotypic variation among populations may indicate local shifts in this balance, or that different stable ‘solutions’ are possible, but testing these alternatives presents a major challenge. In the guppy ( Poecilia reticulata ), a small freshwater fish with male-limited ornamental coloration, these issues can be addressed by transplanting fish among sites of varying predation pressure, thus effectively manipulating the strength and nature of natural selection. Here, we contrast the evolutionary outcome of two such introductions conducted in the Trinidadian El Cedro and Aripo Rivers. We use sophisticated colour appraisal methods that account for full spectrum colour variation and which incorporate the very latest visual sensitivity data for guppies and their predators. Our data indicate that ornamentation evolved along different trajectories: whereas Aripo males evolved more numerous and/or larger orange, black and iridescent markings, El Cedro males only evolved more extensive and brighter iridescence. Examination of the El Cedro experiment also revealed little or no ornamental evolution at the control site over 29 years, which contrasts markedly with the rapid (approx. 2–3 years) changes reported for introduction populations. Finally, whole colour-pattern analysis suggested that the greatest visual difference between El Cedro introduction and control fish would be perceived by the two most salient viewers: guppies and the putatively dangerous predator Crenicichla alta . We discuss whether and how these evolutionary trajectories may result from founder effects, population-specific mate preferences and/or sensory drive.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 18-01-2008
Publisher: Wiley
Date: 09-05-2007
Publisher: The Royal Society
Date: 16-09-2020
Abstract: To be effective, animal colour signals must attract attention—and therefore need to be conspicuous. To understand the signal function, it is useful to evaluate their conspicuousness to relevant viewers under various environmental conditions, including when visual scenes are cluttered by objects of varying colour. A widely used metric of colour difference (Δ S ) is based on the receptor noise limited (RNL) model, which was originally proposed to determine when two similar colours appear different from one another, termed the discrimination threshold (or just noticeable difference). Estimates of the perceptual distances between colours that exceed this threshold—termed ‘suprathreshold’ colour differences—often assume that a colour's conspicuousness scales linearly with colour distance, and that this scale is independent of the direction in colour space. Currently, there is little behavioural evidence to support these assumptions. This study evaluated the relationship between Δ S and conspicuousness in suprathreshold colours using an Ishihara-style test with a coral reef fish, Rhinecanthus aculeatus . As our measure of conspicuousness, we tested whether fish, when presented with two colourful targets, preferred to peck at the one with a greater Δ S from the average distractor colour. We found the relationship between Δ S and conspicuousness followed a sigmoidal function, with high Δ S colours perceived as equally conspicuous. We found that the relationship between Δ S and conspicuousness varied across colour space (i.e. for different hues). The sigmoidal detectability curve was little affected by colour variation in the background or when colour distance was calculated using a model that does not incorporate receptor noise. These results suggest that the RNL model may provide accurate estimates for perceptual distance for small suprathreshold distance colours, even in complex viewing environments, but must be used with caution with perceptual distances exceeding 10 Δ S .
Publisher: Springer Science and Business Media LLC
Date: 07-1990
DOI: 10.1038/346357A0
Publisher: The Royal Society
Date: 05-07-2006
Publisher: The Society for the Study of Evolution
Date: 2005
DOI: 10.1554/04-669.1
Abstract: Animal color pattern phenotypes evolve rapidly. What influences their evolution? Because color patterns are used in communication, selection for signal efficacy, relative to the intended receiver's visual system, may explain and predict the direction of evolution. We investigated this in bowerbirds, whose color patterns consist of plumage, bower structure, and ornaments and whose visual displays are presented under predictable visual conditions. We used data on avian vision, environmental conditions, color pattern properties, and an estimate of the bowerbird phylogeny to test hypotheses about evolutionary effects of visual processing. Different components of the color pattern evolve differently. Plumage sexual dimorphism increased and then decreased, while overall (plumage plus bower) visual contrast increased. The use of bowers allows relative crypsis of the bird but increased efficacy of the signal as a whole. Ornaments do not elaborate existing plumage features but instead are innovations (new color schemes) that increase signal efficacy. Isolation between species could be facilitated by plumage but not ornaments, because we observed character displacement only in plumage. Bowerbird color pattern evolution is at least partially predictable from the function of the visual system and from knowledge of different functions of different components of the color patterns. This provides clues to how more constrained visual signaling systems may evolve.
Publisher: Authorea, Inc.
Date: 02-2023
Publisher: University of Chicago Press
Date: 06-2014
DOI: 10.1086/676093
Publisher: The Company of Biologists
Date: 05-2021
DOI: 10.1242/JEB.241349
Abstract: Producing colored signals often requires consuming dietary carotenoid pigments. Evidence that food deprivation can reduce coloration, however, raises the question of whether other dietary nutrients contribute to signal coloration, and furthermore, whether in iduals can voluntarily select food combinations to achieve optimal coloration. We created a two-way factorial design to manipulate macronutrient and carotenoid access in common mynas (Acridotheres tristis) and measured eye patch coloration as a function of the food combinations in iduals selected. Mynas had access to either water or carotenoid-supplemented water and could either eat a standard captive diet or choose freely between three nutritionally defined pellets (protein, lipid or carbohydrate). Mynas supplemented with both carotenoids and macronutrient pellets had higher color scores than control birds. Male coloration tended to respond more to nutritional manipulation than females, with color scores improving in macronutrient- and carotenoid-supplemented in iduals compared with controls. All mynas consuming carotenoids had higher levels of plasma carotenoids, but only males showed a significant increase by the end of the experiment. Dietary carotenoids and macronutrient intake consumed in combination tended to increase plasma carotenoid concentrations the most. These results demonstrate for the first time that consuming specific combinations of macronutrients along with carotenoids contributes to optimizing a colorful signal, and point to sex-specific nutritional strategies. Our findings improve our knowledge of how diet choices affect signal expression and, by extension, how nutritionally impoverished diets, such as those consumed by birds in cities, might affect sexual selection processes and, ultimately, population dynamics.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 19-01-1973
DOI: 10.1126/SCIENCE.179.4070.243
Abstract: There are many possible spatial patterns of selection and gene flow that can produce a given cline structure the actual geography of natural selection and gene flow must be worked out before an attempt is made to explain a given natural cline in terms of a model. The results of experimental and theoretical models show that it is possible for local differentiation to evolve parapatrically in spite of considerable gene flow if the selection gradients are relatively uniform. Irregularities in environmental gradients increase the sensitivity of clines to the effects of gene flow in proportion to the increase in the differences in gene frequencies between the emigrants and the demes receiving the immigrants. It is not necessary for a sharp spatial environmental change to be present for distinct differentiation to occur. In some cases even a gentle environmental gradient can give rise to marked spatial differentiation along a genetically continuous series of demes such environmental differences may be below the practical limits of resolution in field studies. Any asymmetry in gene flow does not lead to dedifferentiation if the environmental gradient is smooth it merely shifts the position of the transition zone between the differentiated areas from that which would be expected if there were no asymmetry. Abrupt geographic differences in gene, genotype, or morph frequencies should not, therefore, be interpreted as evidence for environmental changes in the immediate vicinity of the steepest part of the cline neither should they be interpreted as evidence for geographic barriers, sharp environmental differences, or sexual isolation among the differentiated groups of populations when there are no other sources of evidence for these phenomena. Gene flow may be unimportant in the differentiation of populations along environmental gradients.
Publisher: Oxford University Press (OUP)
Date: 06-1994
DOI: 10.1093/ICB/34.3.452
Publisher: Walter de Gruyter GmbH
Date: 1991
Publisher: The Royal Society
Date: 05-12-2006
Abstract: Ontogenetic colour change is typically associated with changes in size, vulnerability or habitat, but assessment of its functional significance requires quantification of the colour signals from the receivers' perspective. The tropical python, Morelia viridis , is an ideal species to establish the functional significance of ontogenetic colour change. Neonates hatch either yellow or red and both the morphs change to green with age. Here, we show that colour change from red or yellow to green provides camouflage from visually oriented avian predators in the different habitats used by juveniles and adults. This reflects changes in foraging behaviour and vulnerability as in iduals mature and provides a rare demonstration of the adaptive value of ontogenetic colour change.
Publisher: Cold Spring Harbor Laboratory
Date: 08-06-2018
DOI: 10.1101/342063
Abstract: Colour patterns are used by many species to make decisions that ultimately affect their Darwinian fitness. Colour patterns consist of a mosaic of patches that differ in geometry and visual properties. Although traditionally pattern geometry and colour patch visual properties are analysed separately, these components are likely to work together as a functional unit. Despite this, the combined effect of patch visual properties, patch geometry, and the effects of the patch boundaries on animal visual systems, behaviour and fitness are relatively unexplored. Here we describe Boundary Strength Analysis (BSA), a novel way to combine the geometry of the edges (boundaries among the patch classes) with the receptor noise estimate ( ΔS ) of the intensity of the edges. The method is based upon known properties of vertebrate and invertebrate retinas. The mean and SD of ΔS (m ΔS , s ΔS ) of a colour pattern can be obtained by weighting each edge class ΔS by its length, separately for chromatic and achromatic ΔS . This assumes those colour patterns, or parts of the patterns used in signalling, with larger m ΔS and s ΔS are more stimulating and hence more salient to the viewers. BSA can be used to examine both colour patterns and visual backgrounds. BSA was successful in assessing the estimated conspicuousness of colour pattern variants in two species, guppies ( Poecilia reticulata ) and Gouldian finches ( Erythrura gouldiae ), both polymorphic for patch colour, luminance and geometry. The pattern difference between chromatic and achromatic edges in both species reveals the possibility that chromatic and achromatic edges could function differently. BSA can be applied to any colour pattern used in intraspecific and interspecific behaviour. Seven predictions and four questions about colour patterns are presented.
Publisher: University of Chicago Press
Date: 07-2001
DOI: 10.1086/320862
Abstract: We performed artificial selection on the visual system in guppies (Poecilia reticulata), using the optomotor reaction threshold as the selection criterion. Two lines were selected for increased sensitivity to blue light, two were selected for increased sensitivity to red light, and two were unselected controls. There was significant response to selection in all four selected lines and significant heritability for sensitivity. An examination of the spectral sensitivity function showed that the form of the response differed between the red and blue lines and among the red lines. Such ergence is likely because there are many different mechanisms allowing response to selection for spectral sensitivity. Diverse mechanisms allow a ergent response by different populations to the same selective pressures. Such a mechanism can promote ersity in vision and visual signals, and any multicomponent system where different components can respond to the same selective regime.
Publisher: Elsevier BV
Date: 05-2019
DOI: 10.1016/J.VISRES.2019.02.007
Abstract: Visual pigments can vary across the retina in many vertebrates, but the behavioural consequences of this retinal heterogeneity are unknown. Guppies (Poecilia reticulata) vary dorsoventrally in visual pigments and forage both on the ground and at the water surface, exposing different retinal regions to two very different visual environments. We tested guppy behaviour towards a moving stimulus presented below or above the guppy. We used 12 different narrow-band wavelength stimuli matching each of the opsin peak sensitivities presented either at the top or the bottom of our experimental apparatus. We analysed behaviours of 50 male and 50 female guppies over 4800 trials where a moving stimulus pattern was presented to each guppy. We found that wavelength, position and speed of the stimuli influenced male and female behaviour and seems to be mediated by the long wavelength sensitive photoreceptors. Males also had stronger behavioural responses than females whereas females performed more foraging-related pecking behaviour. Our results suggest that the spatial requirement of visual tasks and their ecological context are important and appear to be partly correlated with photoreceptor arrangement in the retina.
Publisher: Oxford University Press (OUP)
Date: 1980
DOI: 10.2307/2408316
Publisher: University of Chicago Press
Date: 09-1996
DOI: 10.1086/285934
Publisher: Elsevier BV
Date: 1991
DOI: 10.1016/0042-6989(91)90109-I
Abstract: Color patterns of natural populations of guppies (Poecilia reticulata) are a compromise between sexual selection and predation avoidance. Field data on ambient light spectra, water transmission spectra, courtship and attack distances, and cone pigments of guppies and their predators were used to calculate measures of conspicuousness of guppies under various combinations of visual conditions and vision. The results suggest that color patterns are relatively more conspicuous to guppies at the times and places of courtship and relatively less conspicuous at the times and places of maximum predator risk. Some implications to the evolution of vision, visual communication and behavior are discussed.
Publisher: Oxford University Press (OUP)
Date: 03-07-2019
Abstract: In iduals of the same population differ consistently from each other in the average expression of behavioral and physiological traits. Often, such traits are integrated and thus correlated with each other. However, the underlying proximate mechanisms generating and maintaining this among-in idual covariation are still poorly understood. The melanocortin hypothesis suggests that the melanocortin pathways can have pleiotropic effects linking the expression of melanin-based coloration with physiological and behavioral traits. In the present study, we test this hypothesis in adult male guppies (Poecilia reticulata), by estimating among in idual correlations between behaviors (activity, feeding, boldness, display, and chase during courtship), stress response (peak metabolic rate), and coloration (black spot, fuzzy black, and orange). The lack of correlation of any behavior or metabolism with black coloration indicates that the melanocortin hypothesis is not supported in this species. However, we observed covariation among coloration traits, as well as among behavioral traits. Our findings suggest that, although there appear to be constraints within sets of related traits, coloration, physiology, and behaviors can potentially evolve as independent modules in response to selection in this species.
Publisher: Cold Spring Harbor Laboratory
Date: 28-03-2019
DOI: 10.1101/592261
Abstract: To understand the function of colour signals in nature, we require robust quantitative analytical frameworks to enable us to estimate how animal and plant colour patterns appear against their natural background as viewed by ecologically relevant species. Due to the quantitative limitations of existing methods, colour and pattern are rarely analysed in conjunction with one another, despite a large body of literature and decades of research on the importance of spatiochromatic colour pattern analyses. Furthermore, key physiological limitations of animal visual systems such as spatial acuity, spectral sensitivities, photoreceptor abundances and receptor noise levels are rarely considered together in colour pattern analyses. Here, we present a novel analytical framework, called the ‘Quantitative Colour Pattern Analysis’ (QCPA). We have overcome many quantitative and qualitative limitations of existing colour pattern analyses by combining calibrated digital photography and visual modelling. We have integrated and updated existing spatiochromatic colour pattern analyses, including adjacency, visual contrast and boundary strength analysis, to be implemented using calibrated digital photography through the ‘Multispectral Image Analysis and Calibration’ (MICA) Toolbox. This combination of calibrated photography and spatiochromatic colour pattern analyses is enabled by the inclusion of psychophysical colour and luminance discrimination thresholds for image segmentation, which we call ‘Receptor Noise Limited Clustering’, used here for the first time. Furthermore, QCPA provides a novel psycho-physiological approach to the modelling of spatial acuity using convolution in the spatial or frequency domains, followed by ‘Receptor Noise Limited Ranked Filtering’ to eliminate intermediate edge artefacts and recover sharp boundaries following smoothing. We also present a new type of colour pattern analysis, the ‘Local Edge Intensity Analysis’ (LEIA) as well as a range of novel psycho-physiological approaches to the visualisation of spatiochromatic data. QCPA combines novel and existing pattern analysis frameworks into what we hope is a unified, user-friendly, free and open source toolbox and introduce a range of novel analytical and data-visualisation approaches. These analyses and tools have been seamlessly integrated into the MICA toolbox providing a dynamic and user-friendly workflow. QCPA is a framework for the empirical investigation of key theories underlying the design, function and evolution of colour patterns in nature. We believe that it is compatible with, but more thorough than, other existing colour pattern analyses.
Publisher: Wiley
Date: 14-04-2003
Publisher: Elsevier BV
Date: 10-1987
Publisher: Elsevier BV
Date: 12-1982
Publisher: Informa UK Limited
Date: 05-2012
DOI: 10.4161/CIB.19481
Publisher: Cold Spring Harbor Laboratory
Date: 15-12-2022
DOI: 10.1101/2022.12.13.520332
Abstract: The ‘escape and radiate’ hypothesis predicts that once species have evolved aposematism, defended species can utilise more visually erse background habitats as they ‘escape’ the need to be well camouflaged. This enables species to explore new ecological niches, resulting in increased ersification rates. To test the ‘escape’ component of this hypothesis, we examined whether the background habitats of 13 nudibranch mollusc species were more variable for highly defended species (in terms of unpalatability), compared to undefended (palatable) species. We obtained 157 colour pattern statistics from the Quantitative Colour Pattern Analysis (QCPA) framework to analyse backgrounds viewed through the eyes of a potential predator (triggerfish, Rhinecanthus aculeatus ). This was done at viewing distances simulating an escalating predation sequence. Contrary to the hypothesis, we found no significant positive correlations between the ersity of visual backgrounds and the strength of chemical defences, but instead found numerous significant negative correlations. Highly defended species were viewed against backgrounds up to 56.9% less variable than non-defended species. Furthermore, the strongest correlations were found at viewing distances coinciding with likely prey detection and identification. Our results provide empirical evidence against background generalisation in aposematic nudibranch species. Instead, we suggest that less variable visual backgrounds may strengthen aposematic signalling. According to the ‘escape and radiate’ hypothesis, potent chemical defences are thought to enable animals to be less dependent on matching visual backgrounds for camouflage. We investigated this idea in 13 species of nudibranch molluscs and found strong evidence against this hypothesis. In fact, species with strong chemical defences were found on up to 56.9% more uniform backgrounds. This suggests that warning colouration in nudibranchs might be specialised for specific visual backgrounds.
Publisher: University of Chicago Press
Date: 03-2009
DOI: 10.1086/596528
Abstract: Apostatic (frequency- or density-dependent) selection, aposematic signals, and mate choice behavior generally require that the mean prey or potential mate density m value be high enough (above a threshold T) to result in sufficient encounter rates for the searcher to learn or retain the association between conspicuous signals and prey unprofitability, to forage apostatically, or to choose among mates. This assumes that all searchers experience m >T, which implicitly assumes an even dispersion of targets among searcher territories. Uneven dispersion generates new phenomena. If m T) is greater than the increase in the percentage of territories that are favorable. The relationship is reversed when m >T. In both cases, because as few as 10% of the territories can contain 80% of the targets, only a few territory holders may account for most of the selection on most of the target population accidents of experience in only a few searchers can have unexpectedly large effects on the target population. This also provides an explanation for high searcher behavior variation (personalities): in iduals from favorable territories will behave differently in behavioral experiments than those from unfavorable territories, at least with respect to similar kinds of targets. These effects will generate spatial heterogeneity in natural and sexual selection in what are otherwise uniform environments.
Publisher: The Royal Society
Date: 06-06-2018
Abstract: Mimicry of warning signals is common, and can be mutualistic when mimetic species harbour equal levels of defence (Müllerian), or parasitic when mimics are undefended but still gain protection from their resemblance to the model (Batesian). However, whether chemically defended mimics should be similar in terms of toxicity (i.e. causing damage to the consumer) and/or unpalatability (i.e. distasteful to consumer) is unclear and in many studies remains undifferentiated. In this study, we investigated the evolution of visual signals and chemical defences in a putative mimicry ring of nudibranch molluscs. First, we demonstrated that the appearance of a group of red spotted nudibranchs molluscs was similar from the perspective of potential fish predators using visual modelling and pattern analysis. Second, using phylogenetic reconstruction, we demonstrated that this colour pattern has evolved multiple times in distantly related in iduals. Third, we showed that these nudibranchs contained different chemical profiles used for defensive purposes. Finally, we demonstrated that although levels of distastefulness towards Palaemon shrimp remained relatively constant between species, toxicity levels towards brine shrimp varied significantly. We highlight the need to disentangle toxicity and taste when considering chemical defences in aposematic and mimetic species, and discuss the implications for aposematic and mimicry signal evolution.
Publisher: Elsevier BV
Date: 1995
DOI: 10.1016/S0169-5347(00)88956-9
Abstract: Guppies show geographical variation in many different kinds of traits. Traits covary with each other, with predation and with other environmental factors. Phenotypic correlations are often assumed to result from genetic correlations, but may also result from covariation among different sources of natural selection and interactions among the traits' functions. This network of interactions could bias the direction of evolution in characteristic ways, and suggests how intraspecific variation may give rise to interspecific variation.
Publisher: The Company of Biologists
Date: 15-03-2017
DOI: 10.1242/JEB.148544
Abstract: Animals may improve camouflage by both dynamic colour change and local evolutionary adaptation of colour but we have little understanding of their relative importance in colour-changing species. We tested for differences in colour change in response to background colour and light intensity in two populations of central bearded dragon lizards (Pogona vitticeps) representing the extremes in body coloration and geographical range. We found that bearded dragons change colour in response to various backgrounds and that colour change is affected by illumination intensity. Within-in idual colour change was similar in magnitude in the two populations but varied between backgrounds. However, at the endpoints of colour change, each population showed greater similarity to backgrounds that were representative of the local habitat compared with the other population, indicating local adaptation to visual backgrounds. Our results suggest that even in species that change colour, both phenotypic plasticity and geographic ergence of coloration may contribute to improved camouflage.
Publisher: The Royal Society
Date: 06-07-1988
Abstract: Frequency-dependent predation may maintain or prevent colour pattern polymorphisms in prey, and can be caused by a variety of biological phenomena, including perceptual processes (search images), optimal foraging and learning. Most species are preyed upon by more than one predator species, which are likely to differ in foraging styles, perceptual and learning abilities. Depending upon the interaction between predator vision, background and colour pattern parameters, certain morphs may be actively maintained in some conditions and not in others, even with the same predators. More than one kind of predator will also affect stability, and only slight changes in conditions can cause a transition between polymorphism and monomorphism. Frequency-dependent selection is not a panacea for the explanation of variation in animal colour patterns, although it may be important in some systems.
Publisher: The Royal Society
Date: 07-04-2015
Abstract: Colour is an important factor in food detection and acquisition by animals using visually based foraging. Colour can be used to identify the suitability of a food source or improve the efficiency of food detection, and can even be linked to mate choice. Food colour preferences are known to exist, but whether these preferences are heritable and how these preferences evolve is unknown. Using the freshwater fish Poecilia reticulata , we artificially selected for chase behaviour towards two different-coloured moving stimuli: red and blue spots. A response to selection was only seen for chase behaviours towards the red, with realized heritabilities ranging from 0.25 to 0.30. Despite intense selection, no significant chase response was recorded for the blue-selected lines. This lack of response may be due to the motion-detection mechanism in the guppy visual system and may have novel implications for the evolvability of responses to colour-related signals. The behavioural response to several colours after five generations of selection suggests that the colour opponency system of the fish may regulate the response to selection.
Publisher: The Royal Society
Date: 22-05-2014
Abstract: It is often assumed that the primary purpose of a male's sexual display is to provide information about quality, or to strongly stimulate prospective mates, but other functions of courtship displays have been relatively neglected. Male great bowerbirds ( Ptilonorhynchus nuchalis ) construct bowers that exploit the female's predictable field of view (FOV) during courtship displays by creating forced perspective illusions, and the quality of illusion is a good predictor of mating success. Here, we present and discuss two additional components of male courtship displays that use the female's predetermined viewpoint: (i) the rapid and erse flashing of coloured objects within her FOV and (ii) chromatic adaptation of the female's eyes that alters her perception of the colour of the displayed objects. Neither is directly related to mating success, but both are likely to increase signal efficacy, and may also be associated with attracting and holding the female's attention. Signal efficacy is constrained by trade-offs between the signal components there are both positive and negative interactions within multicomponent signals. Important signal components may have a threshold effect on fitness rather than the often assumed linear relationship.
Publisher: Brill
Date: 1970
Abstract: Experiments were performed to test the possible role of the kinesthetic sense in the maintenance of the direction of travel in migrating newts. Two hundred and fifteen Taricha torosa were allowed to orient in an arena open only to the night sky and, after being spun, were allowed to orient again. One hundred and fifty-three came from the area in which the arena was located and sixty-two from a locality 39 airline miles away. "Unspun" newts oriented in the direction that they were travelling when first seen, and a roughly straight-line course was followed. Newts from the distant locality did not orient as well as those captured near the arena. After spinning, random movements or a route determined by the direction of release, was observed. It is concluded that a kinesthetic sense is probably important in helping these animals maintain a straight-line course during their migratory movements.
Publisher: Wiley
Date: 06-1995
DOI: 10.1111/J.1558-5646.1995.TB02278.X
Abstract: We examined the preferences of female guppies (Poecilia reticulata) from 11 localities in Trinidad with respect to male color-pattern elements, body shape and size, and overall color and brightness contrast. Females are on average more attracted to males from their own population than from alien populations, and populations appear to vary in the criteria used in female choice. Multiple-regression analysis suggests that mate-preference criteria vary among localities in intensity, sign, and the number of traits used. Although preference estimators and color-pattern parameters are unique to each population, only orange, black, and color contrast showed a correlation between degree of male trait and degree of preference for that trait. There is a clear effect of water color and a possible effect of predation intensity. The results are discussed in light of various models of sexual selection and the early stages of speciation.
Publisher: Springer Science and Business Media LLC
Date: 09-1983
DOI: 10.1007/BF00690861
Publisher: Elsevier BV
Date: 12-2006
Publisher: Oxford University Press (OUP)
Date: 1982
DOI: 10.2307/2407978
Publisher: Oxford University Press (OUP)
Date: 1982
DOI: 10.2307/2407979
Publisher: Society for Neuroscience
Date: 06-04-2011
DOI: 10.1523/JNEUROSCI.5244-10.2011
Abstract: The cytoplasmic dynein complex is fundamentally important to all eukaryotic cells for transporting a variety of essential cargoes along microtubules within the cell. This complex also plays more specialized roles in neurons. The complex consists of 11 types of protein that interact with each other and with external adaptors, regulators and cargoes. Despite the importance of the cytoplasmic dynein complex, we know comparatively little of the roles of each component protein, and in mammals few mutants exist that allow us to explore the effects of defects in dynein-controlled processes in the context of the whole organism. Here we have taken a genotype-driven approach in mouse ( Mus musculus ) to analyze the role of one subunit, the dynein light intermediate chain 1 ( Dync1li1 ). We find that, surprisingly, an N235Y point mutation in this protein results in altered neuronal development, as shown from in vivo studies in the developing cortex, and analyses of electrophysiological function. Moreover, mutant mice display increased anxiety, thus linking dynein functions to a behavioral phenotype in mammals for the first time. These results demonstrate the important role that dynein-controlled processes play in the correct development and function of the mammalian nervous system.
Publisher: Elsevier BV
Date: 12-2020
Publisher: Public Library of Science (PLoS)
Date: 05-12-2012
Publisher: The Royal Society
Date: 18-08-2017
Abstract: Organisms modify and choose components of their local environments. This ‘niche construction’ can alter ecological processes, modify natural selection and contribute to inheritance through ecological legacies. Here, we propose that niche construction initiates and modifies the selection directly affecting the constructor, and on other species, in an orderly, directed and sustained manner. By dependably generating specific environmental states, niche construction co-directs adaptive evolution by imposing a consistent statistical bias on selection. We illustrate how niche construction can generate this evolutionary bias by comparing it with artificial selection. We suggest that it occupies the middle ground between artificial and natural selection. We show how the perspective leads to testable predictions related to: (i) reduced variance in measures of responses to natural selection in the wild (ii) multiple trait coevolution, including the evolution of sequences of traits and patterns of parallel evolution and (iii) a positive association between niche construction and bio ersity. More generally, we submit that evolutionary biology would benefit from greater attention to the erse properties of all sources of selection.
Publisher: The Royal Society
Date: 06-2014
Abstract: Aposematic signal variation is a paradox: predators are better at learning and retaining the association between conspicuousness and unprofitability when signal variation is low. Movement patterns and variable colour patterns are linked in non-aposematic species: striped patterns generate illusions of altered speed and direction when moving linearly, affecting predators' tracking ability blotched patterns benefit instead from unpredictable pauses and random movement. We tested whether the extensive colour-pattern variation in an aposematic frog is linked to movement, and found that in iduals moving directionally and faster have more elongated patterns than in iduals moving randomly and slowly. This may help explain the paradox of polymorphic aposematism: variable warning signals may reduce protection, but predator defence might still be effective if specific behaviours are tuned to specific signals. The interacting effects of behavioural and morphological traits may be a key to the evolution of warning signals.
Publisher: Springer Science and Business Media LLC
Date: 11-1987
DOI: 10.1007/BF00299966
Publisher: Elsevier BV
Date: 09-2010
DOI: 10.1016/J.CUB.2010.08.033
Abstract: Birds in the infraorder Corvida [1] (ravens, jays, bowerbirds) are renowned for their cognitive abilities [2-4], which include advanced problem solving with spatial inference [4-8], tool use and complex constructions [7-10], and bowerbird cognitive ability is associated with mating success [11]. Great bowerbird males construct bowers with a long avenue from within which females view the male displaying over his bower court [10]. This predictable audience viewpoint is a prerequisite for forced (altered) visual perspective [12-14]. Males make courts with gray and white objects that increase in size with distance from the avenue entrance. This gradient creates forced visual perspective for the audience court object visual angles subtended on the female viewer's eye are more uniform than if the objects were placed at random. Forced perspective can yield false perception of size and distance [12, 15]. After experimental reversal of their size-distance gradient, males recovered their gradients within 3 days, and there was little difference from the original after 2 wks. Variation among males in their forced-perspective quality as seen by their female audience indicates that visual perspective is available for use in mate choice, perhaps as an indicator of cognitive ability. Regardless of function, the creation and maintenance of forced visual perspective is clearly important to great bowerbirds and suggests the possibility of a previously unknown dimension of bird cognition.
Publisher: University of Chicago Press
Date: 06-2015
DOI: 10.1086/681021
Abstract: The world in color presents a dazzling dimension of phenotypic variation. Biological interest in this variation has burgeoned, due to both increased means for quantifying spectral information and heightened appreciation for how animals view the world differently than humans. Effective study of color traits is challenged by how to best quantify visual perception in nonhuman species. This requires consideration of at least visual physiology but ultimately also the neural processes underlying perception. Our knowledge of color perception is founded largely on the principles gained from human psychophysics that have proven generalizable based on comparative studies in select animal models. Appreciation of these principles, their empirical foundation, and the reasonable limits to their applicability is crucial to reaching informed conclusions in color research. In this article, we seek a common intellectual basis for the study of color in nature. We first discuss the key perceptual principles, namely, retinal photoreception, sensory channels, opponent processing, color constancy, and receptor noise. We then draw on this basis to inform an analytical framework driven by the research question in relation to identifiable viewers and visual tasks of interest. Consideration of the limits to perceptual inference guides two primary decisions: first, whether a sensory-based approach is necessary and justified and, second, whether the visual task refers to perceptual distance or discriminability. We outline informed approaches in each situation and discuss key challenges for future progress, focusing particularly on how animals perceive color. Given that animal behavior serves as both the basic unit of psychophysics and the ultimate driver of color ecology/evolution, behavioral data are critical to reconciling knowledge across the schools of color research.
Publisher: Cold Spring Harbor Laboratory
Date: 10-12-2021
DOI: 10.1101/2021.12.08.471400
Abstract: In a variety of aposematic species, the conspicuousness of an in idual’s warning signal and the quantity of its chemical defence are positively correlated. This apparent honest signalling is predicted by resource competition models which assume that the production and maintenance of aposematic defences compete for access to antioxidant molecules that have dual functions as pigments and in protecting against oxidative damage. We raised monarch butterflies ( Danaus plexippus ) on their milkweed host-plants (Apocynaceae) with increasing quantities of cardenolides to test whether (1) the sequestration of secondary defences is associated with costs in the form of oxidative lipid damage and reduced antioxidant defences and (2) that reduced oxidative state can decrease the capacity of in iduals to produce aposematic displays. In male monarchs conspicuousness was explained by an interaction between oxidative damage and sequestration: males with high levels of oxidative damage become less conspicuous with increased sequestration of cardenolides, whereas those with low oxidative damage become more conspicuous with increased levels of cardenolides. There was no significant effect of oxidative damage or concentration of sequestered cardenolides on female conspicuousness. Our results demonstrate a physiological linkage between the production of coloration and protection from autotoxicity, and differential costs of signalling in monarch butterflies.
Publisher: Wiley
Date: 08-2001
DOI: 10.1111/J.0014-3820.2001.TB00684.X
Abstract: Variation among females in mate choice may influence evolution by sexual selection. The genetic basis of this variation is of interest because the elaboration of mating preferences requires additive genetic variation in these traits. Here we measure the repeatability and heritability of two components of female choosiness (responsiveness and discrimination) and of female preference functions for the multiple ornaments borne by male guppies (Poecilia reticulata). We show that there is significant repeatable variation in both components of choosiness and in some preference functions but not in others. There appear to be several male ornaments that females find uniformly attractive and others for which females differ in preference. One consequence is that there is no universally attractive male phenotype. Only responsiveness shows significant additive genetic variation. Variation in responsiveness appears to mask variation in discrimination and some preference functions and may be the most biologically relevant source of phenotypic and genetic variation in mate-choice behavior. To test the potential evolutionary importance of the phenotypic variation in mate choice that we report, we estimated the opportunity for and the intensity of sexual selection under models of mate choice that excluded and that incorporated in idual female variation. We then compared these estimates with estimates based on measured mating success. Incorporating in idual variation in mate choice generally did not predict the outcome of sexual selection any better than models that ignored such variation.
Publisher: The Royal Society
Date: 18-01-2023
Abstract: In a variety of aposematic species, the conspicuousness of an in idual's warning signal and the quantity of its chemical defence are positively correlated. This apparent honest signalling is predicted by resource competition models which assume that the production and maintenance of aposematic defences compete for access to antioxidant molecules that have dual functions as pigments and in protecting against oxidative damage. To test for such trade-offs, we raised monarch butterflies ( Danaus plexippus ) on different species of their milkweed host plants (Apocynaceae) that vary in quantities of cardenolides to test whether (i) the sequestration of cardenolides as a secondary defence is associated with costs in the form of oxidative lipid damage and reduced antioxidant defences and (ii) lower oxidative state is associated with a reduced capacity to produce aposematic displays. In male monarchs conspicuousness was explained by an interaction between oxidative damage and sequestration: males with high levels of oxidative damage became less conspicuous with increased sequestration of cardenolides, whereas those with low oxidative damage became more conspicuous with increased levels of cardenolides. There was no significant effect of oxidative damage or concentration of sequestered cardenolides on female conspicuousness. Our results demonstrate a physiological linkage between the production of coloration and oxidative state, and differential costs of sequestration and signalling in monarch butterflies.
Publisher: American Chemical Society (ACS)
Date: 20-02-2014
DOI: 10.1021/AC404135F
Abstract: Exploiting the distinct excitation and emission properties of concomitant electrochemiluminophores in conjunction with the inherent color selectivity of a conventional digital camera, we create a new strategy for multiplexed electrogenerated chemiluminescence detection, suitable for the development of low-cost, portable clinical diagnostic devices. Red, green and blue emitters can be efficiently resolved over the three-dimensional space of ECL intensity versus applied potential and emission wavelength. As the relative contribution ratio of each emitter to the photographic RGB channels is constant, the RGB ECL intensity versus applied-potential curves could be effectively isolated to a single emitter at each potential.
Publisher: The Company of Biologists
Date: 12-2022
DOI: 10.1242/JEB.244677
Abstract: Edge detection is important for object detection and recognition. However, we do not know whether edge statistics accurately predict the detection of prey by potential predators. This is crucial given the growing availability of image analysis software and their application across non-human visual systems. Here, we investigated whether Boundary Strength Analysis (BSA), Local Edge Intensity Analysis (LEIA) and the Gabor edge disruption ratio (GabRat) could predict the speed and success with which triggerfish (Rhinecanthus aculeatus) detected patterned circular stimuli against a noisy visual background, in both chromatic and achromatic presentations. We found various statistically significant correlations between edge statistics and detection speed depending on treatment and viewing distance however, in idual pattern statistics only explained up to 2% of the variation in detection time, and up to 6% when considering edge statistics simultaneously. We also found changes in fish response over time. While highlighting the importance of spatial acuity and relevant viewing distances in the study of visual signals, our results demonstrate the importance of considering explained variation when interpreting colour pattern statistics in behavioural experiments. We emphasize the need for statistical approaches suitable for investigating task-specific predictive relationships and ecological effects when considering animal behaviour. This is particularly important given the ever-increasing dimensionality and size of datasets in the field of visual ecology.
Publisher: The Royal Society
Date: 22-06-2001
Publisher: Wiley
Date: 03-2007
Publisher: Springer US
Date: 1978
Publisher: The Company of Biologists
Date: 15-11-2021
DOI: 10.1242/JEB.243182
Abstract: Ontogenetic colour change occurs in a ersity of vertebrate taxa and may be closely linked to dietary changes throughout development. In various species, red, orange and yellow colouration can be enhanced by the consumption of carotenoids. However, a paucity of long-term dietary manipulation studies means that little is known of the role of in idual carotenoid compounds in ontogenetic colour change. We know even less about the influence of in idual compounds at different doses (dose effects). The present study aimed to use a large dietary manipulation experiment to investigate the effect of dietary β-carotene supplementation on colouration in southern corroboree frogs (Pseudophryne corroboree) during early post-metamorphic development. Frogs were reared on four dietary treatments with four β-carotene concentrations (0, 1, 2 and 3 mg g−1), with frog colour measured every 8 weeks for 32 weeks. β-Carotene was not found to influence colouration at any dose. However, colouration was found to become more conspicuous over time, including in the control treatment. Moreover, all frogs expressed colour maximally at a similar point in development. These results imply that, for our study species, (1) β-carotene may contribute little or nothing to colouration, (2) frogs can manufacture their own colour, (3) colour development is a continual process and (4) there may have been selection for synchronised development of colour expression. We discuss the potential adaptive benefit of ontogenetic colour change in P. corroboree. More broadly, we draw attention to the potential for adaptive developmental synchrony in the expression of colouration in aposematic species.
Publisher: Springer Science and Business Media LLC
Date: 20-06-2010
Publisher: Wiley
Date: 02-1993
DOI: 10.2307/2937121
Publisher: The Royal Society
Date: 2017
DOI: 10.1098/RSOS.160661
Abstract: Many animals build structures to provide shelter, avoid predation, attract mates or house offspring, but the behaviour and potential cognitive processes involved during building are poorly understood. Great bowerbird ( Ptilinorhynchus nuchalis ) males build and maintain display courts by placing tens to hundreds of objects in a positive size–distance gradient. The visual angles created by the gradient create a forced perspective illusion that females can use to choose a mate. Although the quality of illusion is consistent within males, it varies among males, which may reflect differences in how in iduals reconstruct their courts. We moved all objects off display courts to determine how males reconstructed the visual illusion. We found that all in iduals rapidly created the positive size–distance gradient required for forced perspective within the first 10 objects placed. Males began court reconstruction by placing objects in the centre of the court and then placing objects further out, a technique commonly used when humans lay mosaics. The number of objects present after 72 h was not related to mating success or the quality of the illusion, indicating that male skill at arranging objects rather than absolute number of objects appears to be important. We conclude that differences arise in the quality of forced perspective illusions despite males using the same technique to reconstruct their courts.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 20-01-2012
Abstract: Male bowerbirds build elaborate bowers, or display areas, that consist of an avenue where the female stands and an arena where the male displays. Males decorate their arenas meticulously with stones, flowers, and found objects. Previous work has shown that these bowers induce forced perspective illusions in the observing females. Now Kelley and Endler (p. 335 see the Perspective by Anderson ) show that mating success is based on components of the illusion, rather than the physical nature of the bower. Thus, females choose their mates based on a visual illusion painstakingly constructed and maintained by the displaying male.
Publisher: Cold Spring Harbor Laboratory
Date: 02-2023
DOI: 10.1101/2023.01.30.525844
Abstract: Predators learn and memorise the association between conspicuous colour patterns of aposematic prey and their underlying chemical or secondary defences. Consequently, variation in signal design within a species should be selected against, because it can decrease the rate of predator learning and enhance the rates of predator errors. However, quantitative assessments have not been made on whether the strength of chemical defences influences colour pattern variation. We examined this by quantifying colour pattern variation using Quantitative Colour Pattern Analysis (QCPA) in 12 Dorid nudibranch species (Infraorder: Doridoidei) that varied in their unpalatability. We accounted for the physiological limitations of a potential predator’s visual system (a triggerfish, Rhinecanthus aculeatus ), modelling animal appearance along an escalating predation sequence. We found that various colour pattern statistics were less variable in highly unpalatable species, with pattern statistics being up to 72% less variable than those of more palatable species. No correlations indicating the opposite were found across 157 colour pattern statistics. However, the strength and number of correlations depended on viewing distance. Our results suggest that low colour pattern variability could be favourable for aposematic signalling in Dorid nudibranchs. We provide evidence for distance-dependent signalling facilitating context-specific feature selection in multicomponent visual signals.
Publisher: Wiley
Date: 30-07-2018
DOI: 10.1111/EVO.13519
Abstract: Light environments critically impact species that rely on vision to survive and reproduce. Animal visual systems must accommodate changes in light that occur from minutes to years, yet the mechanistic basis of their response to spectral (color) changes is largely unknown. Here, we used a laboratory experiment where replicate guppy populations were kept under three different light environments for up to 8-12 generations to explore possible differences in the expression levels of nine guppy opsin genes. Previous evidence for opsin expression-light environment "tuning" has been either correlative or focused exclusively on the relationship between the light environment and opsin expression over one or two generations. In our multigeneration experiment, the relative expression levels of nine different guppy opsin genes responded differently to light environment changes: some did not respond, while others differed due to phenotypic plasticity. Moreover, for the LWS-1 opsin we found that, while we observed a wide range of plastic responses under different light conditions, common plastic responses (where the population replicates all followed the same trajectory) occurred only after multigenerational exposure to different light environments. Taken together this suggests that opsin expression plasticity plays an important role in light environment "tuning" in different light environments on different time scales, and, in turn, has important implications for both visual system function and evolution.
Publisher: Elsevier BV
Date: 06-2019
DOI: 10.1016/J.VISRES.2019.04.002
Abstract: Accurate knowledge of species colour discrimination is fundamental to explain colour based behaviours and the evolution of colour patterns. We tested how the receptor noise limited model, widely used in behavioural ecology, matched actual colour discrimination thresholds obtained using behavioural tests. Guppies (Poecilia reticulata) were first trained to push a target coloured disk placed among eight grey disks of various luminances on a grey plate. Guppies were then tested to find target disks, which varied in colour contrast from the plate. The target disks followed a gradient going from high contrast to inconspicuous against the grey background. We plotted the percentage of correct choices of each colour in the gradient against the model prediction and determined the discrimination thresholds using the inflection point of the fitted sigmoid curve. We performed the experiment on six colour gradients: red, orange, yellow, green, blue and purple. Four colour gradients: red, orange, green and blue, showed a discrimination threshold that matched the model predictions. However, deviations of the model for the yellow and purple gradients suggest that ecological relevance of some colours could affect decision-making in behavioural tests and that we can no longer assume that the rules for colour discrimination are independent of colours.
Publisher: Elsevier BV
Date: 08-2019
Publisher: Elsevier BV
Date: 11-2005
DOI: 10.1016/J.TREE.2005.07.011
Abstract: The theory of warning signals dates back to Wallace but is still confusing, controversial and complex. Because predator avoidance of warningly coloured prey (aposematism) is based upon learning and reinforcement, it is difficult to understand how initially rare conspicuous forms subsequently become common. Here, we discuss several possible resolutions to this apparent paradox. Many of these ideas have been largely ignored as a result of implicit assumptions about predator behaviour and assumed lack of variation in the predators, prey and the predation process. Considering the spatial and temporal variation in and mechanisms of behaviour of both predators and prey will make it easier to understand the process and evolution of aposematism.
Publisher: Informa UK Limited
Date: 15-03-2018
Publisher: University of Chicago Press
Date: 03-1992
DOI: 10.1086/285308
Publisher: Springer Science and Business Media LLC
Date: 13-11-2013
Abstract: One of the most striking features of avian vision is the variation in spectral sensitivity of the short wavelength sensitive (SWS1) opsins, which can be ided into two sub-types: violet- and UV- sensitive (VS & UVS). In birds, UVS has been found in both passerines and parrots, groups that were recently shown to be sister orders. While all parrots are thought to be UVS, recent evidence suggests some passerine lineages may also be VS. The great bowerbird ( Chlamydera nuchalis ) is a passerine notable for its courtship behaviours in which males build and decorate elaborate bower structures. The great bowerbird SWS1 sequence possesses an unusual residue combination at known spectral tuning sites that has not been previously investigated in mutagenesis experiments. In this study, the SWS1 opsin of C. nuchalis was expressed along with a series of spectral tuning mutants and ancestral passerine SWS1 pigments, allowing us to investigate spectral tuning mechanisms and explore the evolution of UV/violet sensitivity in early passerines and parrots. The expressed C. nuchalis SWS1 opsin was found to be a VS pigment, with a λ max of 403 nm. Bowerbird SWS1 mutants C86F, S90C, and C86S/S90C all shifted λ max into the UV, whereas C86S had no effect. Experimentally recreated ancestral passerine and parrot asserine SWS1 pigments were both found to be VS, indicating that UV sensitivity evolved independently in passerines and parrots from a VS ancestor. Our mutagenesis studies indicate that spectral tuning in C. nuchalis is mediated by mechanisms similar to those of other birds. Interestingly, our ancestral sequence reconstructions of SWS1 in landbird evolution suggest multiple transitions from VS to UVS, but no instances of the reverse. Our results not only provide a more precise prediction of where these spectral sensitivity shifts occurred, but also confirm the hypothesis that birds are an unusual exception among vertebrates where some descendants re-evolved UVS from a violet type ancestor. The re-evolution of UVS from a VS type pigment has not previously been predicted elsewhere in the vertebrate phylogeny.
Publisher: Springer Science and Business Media LLC
Date: 26-05-2015
Publisher: Wiley
Date: 21-10-2016
DOI: 10.1111/JEB.12984
Abstract: Phenotypic traits such as ornaments and armaments are generally shaped by sexual selection, which often favours larger and more elaborate males compared to females. But can sexual selection also influence the brain? Previous studies in vertebrates report contradictory results with no consistent pattern between variation in brain structure and the strength of sexual selection. We hypothesize that sexual selection will act in a consistent way on two vertebrate brain regions that directly regulate sexual behaviour: the medial preoptic nucleus (MPON) and the ventromedial hypothalamic nucleus (VMN). The MPON regulates male reproductive behaviour whereas the VMN regulates female reproductive behaviour and is also involved in male aggression. To test our hypothesis, we used high-resolution magnetic resonance imaging combined with traditional histology of brains in 14 dragon lizard species of the genus Ctenophorus that vary in the strength of precopulatory sexual selection. Males belonging to species that experience greater sexual selection had a larger MPON and a smaller VMN. Conversely, females did not show any patterns of variation in these brain regions. As the volumes of both these regions also correlated with brain volume (BV) in our models, we tested whether they show the same pattern of evolution in response to changes in BV and found that the do. Therefore, we show that the primary brain nuclei underlying reproductive behaviour in vertebrates can evolve in a mosaic fashion, differently between males and females, likely in response to sexual selection, and that these same regions are simultaneously evolving in concert in relation to overall brain size.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 15-06-1990
DOI: 10.1126/SCIENCE.248.4961.1405
Abstract: Sexual selection may explain why secondary sexual traits of males are so strongly developed in some species that they seem maladaptive. Female mate choice appears to favor the evolution of conspicuous color patterns in male guppies (Poecilia reticulata) from Trinidad, but color patterns vary strikingly among populations. According to most theory, correlated evolution of female mating preferences and preferred male traits within populations could promote this kind of ergence between populations. But mating preferences could also constrain the evolution of male traits. In some guppy populations, females discriminate among males based on variation in the extent of orange pigment in male color patterns, and populations differ significantly in the degree offemale preferences for orange area. In a comparison ofseven populations, the degree offemale preference based on orange is correlated with the population average orange area. Thus male traits and female preferences appear to be evolving in parallel.
Publisher: Public Library of Science (PLoS)
Date: 22-09-2020
Publisher: Wiley
Date: 08-2005
Publisher: Springer Science and Business Media LLC
Date: 04-1988
DOI: 10.1038/332593B0
Publisher: Elsevier BV
Date: 08-1989
DOI: 10.1016/0169-5347(89)90171-7
Abstract: The Hamilton-Zuk hypothesis for parasite-mediated sexual selection in animals has generated much controversy. To resolve the arguments it will be necessary to incorporate many more details of the biology, ecology and evolution of hosts and parasites into studies of sexual selection.
Publisher: The Royal Society
Date: 28-06-2023
Abstract: Diurnal biting flies are strongly attracted to blue objects. This behaviour is widely exploited for fly control, but its functional significance is debated. It is hypothesized that blue objects resemble animal hosts blue surfaces resemble shaded resting places and blue attraction is a by-product of attraction to polarized light. We computed the fly photoreceptor signals elicited by a large s le of leaf and animal integument reflectance spectra, viewed under open/cloudy illumination and under woodland shade. We then trained artificial neural networks (ANNs) to distinguish animals from leaf backgrounds, and shaded from unshaded surfaces, in order to find the optimal means of doing so based upon the sensory information available to a fly. After training, we challenged ANNs to classify blue objects used in fly control. Trained ANNs could make both discriminations with high accuracy. They discriminated animals from leaves based upon blue–green photoreceptor opponency and commonly misclassified blue objects as animals. Meanwhile, they discriminated shaded from unshaded stimuli using achromatic cues and never misclassified blue objects as shaded. We conclude that blue–green opponency is the most effective means of discriminating animals from leaf backgrounds using a fly's sensory information, and that blue objects resemble animal hosts through such mechanisms.
Publisher: Oxford University Press (OUP)
Date: 28-06-2012
Publisher: Annual Reviews
Date: 11-1988
Publisher: Springer Science and Business Media LLC
Date: 23-09-2016
Publisher: Oxford University Press (OUP)
Date: 06-1998
Publisher: Oxford University Press (OUP)
Date: 30-11-2020
Abstract: The presence of various combinations of adjacent colors within polymorphic species’ color pattern could have a major impact on mate choice. We studied the role of pattern geometry in predicting mate choice in guppies using boundary strength analysis (BSA). BSA estimates the visual contrast intensity between two adjacent color patches (ΔS) weighted by the lengths of the boundaries between these adjacent color patches. We measured both the chromatic (hue and saturation) and achromatic (luminance) ΔS for each pair of adjacent patches. For each male’s color pattern, we measured BSA as both mean (mΔS) and coefficient of variation (cvΔS) of all ΔS weighted by their corresponding boundary lengths. We also determined if specific color patch boundaries had an impact on female preferences and whether these predicted overall male contrast (mΔS). We found that males with a higher mΔS were more attractive to females and that six boundaries containing either fuzzy black or black as one of the pair colors significantly affected female preferences, indicating that 1) females favored highly conspicuous males and 2) melanin-based patches could be used as a signal lifier, not only for orange but for other colors.
Publisher: Wiley
Date: 25-07-2018
DOI: 10.1111/JEB.13342
Abstract: The sensory drive hypothesis predicts that across different light environments sexually selected colour patterns will change to increase an animal's visual communication efficiency within different habitats. This is because in iduals with more efficient signal components are likely to have more successful matings and hence produce more offspring. However, how colour pattern signals change over multiple generations under different light environmental conditions has not been tested experimentally. Here, we manipulated colour pattern signal efficiency by providing different ambient light environments over multiple generations to examine whether male colour pattern components change within large replicated populations of guppies (Poecilia reticulata). We report that colour patches change within populations over time and are phenotypically different among our three different light environments. Visual modelling suggests that the majority of these changes can be understood by considering the chroma, hue and luminance of each colour patch as seen by female guppies under each light environment. Taken together, our results support the hypothesis that different environmental conditions during signal reception can directly or indirectly drive the phenotypic ersification of visual signals within species.
Publisher: Oxford University Press (OUP)
Date: 06-1995
DOI: 10.2307/2410270
Publisher: University of Chicago Press
Date: 11-1975
DOI: 10.1086/283036
Abstract: Suppose we have a cline in gene frequency which results from spatially varying selection forces (which tend to establish the cline) opposed by gene flow (which tends to blur the cline). The characteristic width, W, of this gene frequency cline can be assessed qualitatively in terms of the parameters characterizing the selection and gene flow processes. We define Δ as the transition distance in the selection gradient, s as the maximum selection intensity (see fig. 1), l as the root-mean-square gene flow distance (see eq. [3]), and l
Publisher: MDPI AG
Date: 07-09-2022
Abstract: Male guppies (Poecilia reticulata) have multiple colored spots and perform courtship displays near the edges of streams in Trinidad in shallow water flowing through rainforest. Depending upon the orientation of the pair, the female sees the male displays against gravel or other stream bed substrates or against the spacelight—the roughly uniform light coming from the water column away from the bank. We observed courting pairs in two adjacent natural streams and noted the directions of each male display. We found that the female sees the male more often against spacelight than against gravel when females either faced the spacelight from the opposite bank or from downstream, or both. Visual modelling using natural substrate reflectances and field light measurements showed higher chromatic contrast of males against spacelight than against substrates independent of the two ambient light environments used during displays, but achromatic contrast depended upon the ambient light habitat. This suggests that courtship involves both chromatic and achromatic contrast. We conclude that the orientation of courting pairs and the ambient light spectrum should be accounted for in studies of mate choice, because the visual background and light affect visibility, and these differ with orientation.
Publisher: Elsevier BV
Date: 10-2012
Publisher: Wiley
Date: 08-04-2019
Publisher: Cold Spring Harbor Laboratory
Date: 21-10-2022
DOI: 10.1101/2022.10.20.513115
Abstract: Great bowerbird males build bowers for attracting females for mating. Bowers consist of a thatched twig tunnel (avenue) which opens onto two flat courts covered with objects. Male displays on a court are seen by a female from within the avenue. She sees and hears displays through the avenue entrance but can only see the male’s head and objects in his bill as it passes repeatedly across the entrance. We investigated bower acoustic properties by playing standard sounds from multiple court positions and recorded the resulting sounds at the female’s typical avenue head position within the avenue. Bower geometry significantly affects both his acoustic and visual display components and physically synchronizes them as he repeatedly moves in and out of the female’s view. Consequently, complex neural circuitry is unnecessary for linking sound to vision. Experimentally removing bower objects shows that objects significantly increase higher frequencies, hence bandwidth and loudness received inside the avenue. Great Bowerbird bowers produce a synchronized multimodal signal to females which may increase male attractiveness more than if a single sensory mode were used. This multimodal signal is unusual in that it is constructed rather than being part of the body and synchronized as a result of physics rather than neurons. Bowerbird bower geometry jointly effects both visual and auditory signal components and synchronizes them without the need for additional neural circuitry.
Publisher: Wiley
Date: 27-12-2016
DOI: 10.1111/JBI.12942
Publisher: University of Chicago Press
Date: 04-2004
DOI: 10.1086/382662
Abstract: Conspicuous warning signals of unprofitable prey are a defense against visually hunting predators. They work because predators learn to associate unprofitability with bright coloration and because strong signals are detectable and memorable. However, many species that can be considered defended are not very conspicuous they have weak warning signals. This phenomenon has previously been ignored in models and experiments. In addition, there is significant within- and among-species variation among predators in their search behavior, in their visual, cognitive, and learning abilities, and in their resistance to defenses. In this article we explore the effects of variable predators on models that combine positive frequency-dependent, frequency-independent, and negative frequency-dependent predation and show that weak signaling of aposematic species can evolve if predators vary in their tendency to attack defended prey.
Publisher: The Royal Society
Date: 28-09-2016
Abstract: The appearance of animal colour signals depends jointly upon the ambient light spectrum and the signal's reflectance spectra. Light environment heterogeneity might, therefore, allow in iduals to enhance their signal by signalling in an environment that increases signal efficacy. We tested this hypothesis by providing male guppies ( Poecilia reticulata ), a choice of three light environments in which to display their colour signal to females: green, lilac, and clear. We paired males with both receptive and non-receptive females to test whether female response might affect male behavioural decisions. Males preferred the clear environment in all trials and this environment also resulted in males having the highest average visual contrast. Sexual behaviour was influenced by complex interactions between female receptivity, light environment, and male colour pattern contrast. Males spent significantly more time in the environment in which their colour signal had the highest contrast, but only when paired with receptive females. Significant interactions between light environment and in idual male colour components were also seen only in receptive trials. Our results suggest that males use light environment to enhance their colour pattern, but only in the presence of receptive females.
Publisher: Public Library of Science (PLoS)
Date: 27-11-2013
Publisher: American Association for the Advancement of Science (AAAS)
Date: 02-06-2017
Abstract: In a rare parallel with human instrumental music, wild palm cockatoos manufacture sound tools and produce a rhythmic beat.
Publisher: University of Chicago Press
Date: 12-2016
DOI: 10.1086/688765
Abstract: Animal coloration has multiple functions including thermoregulation, camouflage, and social signaling, and the requirements of each function may sometimes conflict. Many terrestrial ectotherms accommodate the multiple functions of color through color change. However, the relative importance of these functions and how color-changing species accommodate them when they do conflict are poorly understood because we lack data on color change in the wild. Here, we show that the color of in idual radio-tracked bearded dragon lizards, Pogona vitticeps, correlates strongly with background color and less strongly, but significantly, with temperature. We found no evidence that in iduals simultaneously optimize camouflage and thermoregulation by choosing light backgrounds when hot or dark backgrounds when cold. In laboratory experiments, lizards showed both UV-visible (300-700 nm) and near-infrared (700-2,100 nm) reflectance changes in response to different background and temperature treatments, consistent with camouflage and thermoregulatory functions, respectively, but with no interaction between the two. Overall, our results suggest that wild bearded dragons change color to improve both thermoregulation and camouflage but predominantly adjust for camouflage, suggesting that compromising camouflage may entail a greater potential immediate survival cost.
Publisher: The Royal Society
Date: 15-06-2016
Abstract: Many terrestrial ectotherms are capable of rapid colour change, yet it is unclear how these animals accommodate the multiple functions of colour, particularly camouflage, communication and thermoregulation, especially when functions require very different colours. Thermal benefits of colour change depend on an animal's absorptance of solar energy in both UV–visible (300–700 nm) and near-infrared (NIR 700–2600 nm) wavelengths, yet colour research has focused almost exclusively on the former. Here, we show that wild-caught bearded dragon lizards ( Pogona vitticeps ) exhibit substantial UV–visible and NIR skin reflectance change in response to temperature for dorsal but not ventral (throat and upper chest) body regions. By contrast, lizards showed the greatest temperature-independent colour change on the beard and upper chest during social interactions and as a result of circadian colour change. Biophysical simulations of heat transfer predicted that the maximum temperature-dependent change in dorsal reflectivity could reduce the time taken to reach active body temperature by an average of 22 min per active day, saving 85 h of basking time throughout the activity season. Our results confirm that colour change may serve a thermoregulatory function, and competing thermoregulation and signalling requirements may be met by partitioning colour change to different body regions in different circumstances.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 20-07-2012
Abstract: Borgia et al . raise some questions about our recent study showing that great bowerbirds create visual illusions that are used in mate choice. We address them by providing further details about our methods and results. We also provide detailed descriptions of our geometric calculations to address their measurement and analysis questions.
Publisher: Elsevier BV
Date: 10-1998
DOI: 10.1016/S0169-5347(98)01471-2
Abstract: During courtship, signals are sent between the sexes, and received signals contain information that forms the basis of decision making. Much is known about signal content, but less is known about signal design-what makes signals work efficiently? A consideration of design not only gives new insights into the evolution of signals (including novelty), but also allows the development of specific and testable predictions about the direction of evolution. Recently there has been increased interest in signal design, but this has resulted in some apparently ergent views in the literature.
Publisher: Wiley
Date: 28-09-2011
DOI: 10.1111/J.1420-9101.2011.02387.X
Abstract: Variation in static allometry, the power relationship between character size and body size among in iduals at similar developmental stages, remains poorly understood. We tested whether predation or other ecological factors could affect static allometry by comparing the allometry between the caudal fin length and the body length in adult male guppies (Poecilia reticulata) among populations from different geographical areas, exposed to different predation pressures. Neither the allometric slopes nor the allometric elevations (intercept at constant slope) changed with predation pressure. However, populations from the Northern Range in Trinidad showed allometry with similar slopes but lower intercepts than populations from the Caroni and the Oropouche drainages. Because most of these populations are exposed to predation by the prawn Macrobrachium crenulatum, we speculated that the specific selection pressures exerted by this predator generated this change in relative caudal fin size, although effects of other environmental factors could not be ruled out. This study further suggests that the allometric elevation is more variable than the allometric slope.
Publisher: The Company of Biologists
Date: 2019
DOI: 10.1242/JEB.189787
Abstract: Colour vision mediates ecologically relevant tasks for many animals, such as mate choice, foraging and predator avoidance. However, our understanding of animal colour perception is largely derived from human psychophysics, and behavioural tests of non-human animals are required to understand how colour signals are perceived. Here, we introduce a novel test of colour vision in animals inspired by the Ishihara colour charts, which are widely used to identify human colour deficiencies. In our method, distractor dots have a fixed chromaticity (hue and saturation) but vary in luminance. Animals can be trained to find single target dots that differ from distractor dots in chromaticity. We provide MATLAB code for creating these stimuli, which can be modified for use with different animals. We demonstrate the success of this method with triggerfish, Rhinecanthus aculeatus, which quickly learnt to select target dots that differed from distractor dots, and highlight behavioural parameters that can be measured, including success of finding the target dot, time to detection and error rate. We calculated discrimination thresholds by testing whether target colours that were of increasing colour distances (ΔS) from distractor dots could be detected, and calculated discrimination thresholds in different directions of colour space. At least for some colours, thresholds indicated better discrimination than expected from the receptor noise limited (RNL) model assuming 5% Weber fraction for the long-wavelength cone. This methodology could be used with other animals to address questions such as luminance thresholds, sensory bias, effects of sensory noise, colour categorization and saliency.
Publisher: Wiley
Date: 06-02-2012
Publisher: Elsevier BV
Date: 03-2021
Publisher: The Royal Society
Date: 07-06-2023
Abstract: Coloration facilitates evolutionary investigations in nature because the interaction between genotype, phenotype and environment is relatively accessible. In a landmark set of studies, Endler addressed this complexity by demonstrating that the evolution of male Trinidadian guppy coloration is shaped by the local balance between selection for mate attractiveness versus crypsis. This became a textbook paradigm for how antagonistic selective pressures may determine evolutionary trajectories in nature. However, recent studies have challenged the generality of this paradigm. Here, we respond to these challenges by reviewing five important yet underappreciated factors that contribute to colour pattern evolution: (i) among-population variation in female preference and correlated variation in male coloration, (ii) differences in how predators versus conspecifics view males, (iii) biased assessment of pigmentary versus structural coloration, (iv) the importance of accounting for multi-species predator communities, and (v) the importance of considering the multivariate genetic architecture and multivariate context of selection and how sexual selection encourages polymorphic ergence. We elaborate these issues using two challenging papers. Our purpose is not to criticize but to point out the potential pitfalls in colour research and to emphasize the depth of consideration necessary for testing evolutionary hypotheses using complex multi-trait phenotypes such as guppy colour patterns.
Publisher: Wiley
Date: 02-12-2019
Publisher: Elsevier BV
Date: 2015
Publisher: American Association for the Advancement of Science (AAAS)
Date: 22-07-2005
Abstract: Brilliant plumage is typical of male birds, reflecting differential enhancement of male traits when females are the limiting sex. Brighter females are thought to evolve exclusively in response to sex role reversal. The striking reversed plumage dichromatism of Eclectus roratus parrots does not fit this pattern. We quantify plumage color in this species and show that very different selection pressures are acting on males and females. Male plumage reflects a compromise between the conflicting requirements for camouflage from predators while foraging and conspicuousness during display. Females are liberated from the need for camouflage but compete for rare nest hollows.
Publisher: Proceedings of the National Academy of Sciences
Date: 03-12-2012
Abstract: Males often produce elaborate displays that increase their attractiveness to females, and some species extend their displays to include structures or objects that are not part of their body. Such “extended phenotypes” may communicate information that cannot be transmitted by bodily signals or may provide a more reliable signal than bodily signals. However, it is unclear whether these signals are in idually distinct and whether they are consistent over long periods of time. Male bowerbirds construct and decorate bowers that function in mate choice. Bower display courts constructed by male great bowerbirds ( Ptilonorhynchus nuchalis ) induce a visual illusion known as forced perspective for the female viewing the male’s display over the court, and the quality of illusion is associated with mating success. We improved the quality of the forced perspective to determine whether males maintained it at the new higher level, decreased the perspective quality back to its original value, or allowed it to decay at random over time. We found that the original perspective quality was actively recovered to in idual original values within 3 d. We measured forced perspective over the course of one breeding season and compared the forced perspective of in idual males between two successive breeding seasons. We found that differences in the quality of visual illusion among males were consistent within and between two breeding seasons. This suggests that forced perspective is actively and strongly maintained at a different level by each in idual male.
Publisher: The Royal Society
Date: 29-05-1993
Abstract: Animal communication systems have evolved so that in iduals can make decisions based upon the behaviour, physiology or morphology of others. Receiving mechanism s probably evolve to increase the efficiency and reliability of information reception whereas signals probably evolve to increase the efficiency of communication and reliability of manipulation of the receiving in idual to the benefit of the emitter. The minimum requirement for clear reception suggests that any study of the evolution and design of communication systems must consider the factors that affect the quality of the received and processed signal. Critical information is needed about how the signal is generated and emitted, how it fares during transmission through air, water or substrate, how it is received and processed by the receiver’s sensory and cognitive systems, and the factors which affect the fitness consequences of alternative ways of reacting to the information contained in the signal. These should allow predictions about the kinds and forms of signals used by animals signalling under known conditions. Phylogenetic history, and the geological time a clade spends in different signalling environments, will also affect signal evolution, and hence the success of predictions about signal design. W e need to use methods of m any different biological fields to understand the design and evolution of signals and signalling systems.
Publisher: Springer Berlin Heidelberg
Date: 1983
Publisher: The Royal Society
Date: 04-2017
Abstract: Deimatic or ‘startle’ displays cause a receiver to recoil reflexively in response to a sudden change in sensory input. Deimatism is sometimes implicitly treated as a form of aposematism (unprofitability associated with a signal). However, the fundamental difference is, in order to provide protection, deimatism does not require a predator to have any learned or innate aversion. Instead, deimatism can confer a survival advantage by exploiting existing neural mechanisms in a way that releases a reflexive response in the predator. We discuss the differences among deimatism, aposematism, and forms of mimicry, and their ecological and evolutionary implications. We highlight outstanding questions critical to progress in understanding deimatism.
Publisher: Oxford University Press (OUP)
Date: 05-1982
DOI: 10.1093/ICB/22.2.349
Publisher: The Royal Society
Date: 07-05-2015
Abstract: Ornamentation of parents poses a high risk for offspring because it reduces cryptic nest defence. Over a century ago, Wallace proposed that sexual dichromatism enhances crypsis of open-nesting females although subsequent studies found that dichromatism per se is not necessarily adaptive. We tested whether reduced female ornamentation in a sexually dichromatic species reduces the risk of clutch depredation and leads to adaptive parental roles in the red-capped plover Charadrius ruficapillus, a species with biparental incubation. Males had significantly brighter and redder head coloration than females. During daytime, when visually foraging predators are active, colour-matched model males incurred a higher risk of clutch depredation than females, whereas at night there was no difference in depredation risk between sexes. In turn, red-capped plovers maintained a strongly diurnal/nocturnal ision of parental care during incubation, with males attending the nest largely at night when visual predators were inactive and females incubating during the day. We found support for Wallace's conclusion that reduced female ornamentation provides a selective advantage when reproductive success is threatened by visually foraging predators. We conclude that predators may alter their prey's parental care patterns and therefore may affect parental cooperation during care.
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for John Endler.