scholarly journals Linking the evolution and form of warning coloration in nature

2011 ◽  
Vol 279 (1728) ◽  
pp. 417-426 ◽  
Author(s):  
Martin Stevens ◽  
Graeme D. Ruxton
Keyword(s):  
Mate Choice ◽  
Evolutionary Ecology ◽  
Classical System ◽  
Warning Signal ◽  
Current Understanding ◽  
Warning Coloration ◽  
Warning Signals ◽  
Initial Evolution ◽  
Mechanistic Basis ◽  
Future Work

Many animals are toxic or unpalatable and signal this to predators with warning signals (aposematism). Aposematic appearance has long been a classical system to study predator–prey interactions, communication and signalling, and animal behaviour and learning. The area has received considerable empirical and theoretical investigation. However, most research has centred on understanding the initial evolution of aposematism, despite the fact that these studies often tell us little about the form and diversity of real warning signals in nature. In contrast, less attention has been given to the mechanistic basis of aposematic markings; that is, ‘what makes an effective warning signal?’, and the efficacy of warning signals has been neglected. Furthermore, unlike other areas of adaptive coloration research (such as camouflage and mate choice), studies of warning coloration have often been slow to address predator vision and psychology. Here, we review the current understanding of warning signal form, with an aim to comprehend the diversity of warning signals in nature. We present hypotheses and suggestions for future work regarding our current understanding of several inter-related questions covering the form of warning signals and their relationship with predator vision, learning, and links to broader issues in evolutionary ecology such as mate choice and speciation.

Aposematism

2018 ◽  
Author(s):  
Graeme D. Ruxton ◽  
William L. Allen ◽  
Thomas N. Sherratt ◽  
Michael P. Speed
Keyword(s):  
Secondary Effects ◽  
Warning Coloration ◽  
Common Features ◽  
Initial Evolution ◽  
The Common ◽  
Aposematic Signals

Aposematism is the pairing of two kinds of defensive phenotype: an often repellent secondary defence that typically renders prey unprofitable to predators if they attack them and some evolved signal that indicates the presence of that defence. Aposematic signals often work to modify the behaviours of predators both before and during attacks. Warning coloration, for example, may increase wariness and hence improve the chances that a chemically defended prey is released unharmed after an attack. An aposematic signal may therefore first tend to reduce the probability that a predator commences attack (a primary defence) and then (as a component of secondary defence) reduce the probability that the prey is injured or killed during any subsequent attack. In this chapter we will consider both the primary and the secondary effects of aposematic signals on prey protection. We begin first by describing the common features of aposematic signals and attempting to show the wide use to which aposematic signalling is deployed across animals (and perhaps plants too). We then review the interesting evolutionary issues aposematic signals raise, including their initial evolution and their integration with sexual and other signals. We also discuss important ecological, co-evolutionary, and macroevolutionary consequences of aposematism.

Introduction

2018 ◽  
Author(s):  
Graeme D. Ruxton ◽  
William L. Allen ◽  
Thomas N. Sherratt ◽  
Michael P. Speed
Keyword(s):  
Evolutionary Ecology ◽  
The State ◽  
Warning Signals ◽  
The Many

In 2004, the first edition of ‘Avoiding Attack: The Evolutionary Ecology of Crypsis, Warning Signals, and Mimicry’ by Ruxton et al. was published. The book aimed to provide a systematic and up-to-date review and synthesis of widespread anti-predator defences. In it, we focussed on sensorially mediated defences and the many factors that underpin these adaptations, aiming to set out the state-of-understanding in the fascinating world of anti-predator adaptations, and highlight which topics within the field seem most ripe for further investigation....

scholarly journals Stabilizing selection on individual pattern elements of aposematic signals

2017 ◽  
Vol 284 (1861) ◽  
pp. 20170926 ◽  
Author(s):  
Anne E. Winters ◽  
Naomi F. Green ◽  
Nerida G. Wilson ◽  
Martin J. How ◽  
Mary J. Garson ◽  
...  
Keyword(s):  
Pattern Analysis ◽  
Marine Organism ◽  
Warning Signal ◽  
Colour Pattern ◽  
Stabilizing Selection ◽  
Warning Signals ◽  
Fish Predator ◽  
Selection For ◽  
Aposematic Signals ◽  
Behavioural Experiments

Warning signal variation is ubiquitous but paradoxical: low variability should aid recognition and learning by predators. However, spatial variability in the direction and strength of selection for individual elements of the warning signal may allow phenotypic variation for some components, but not others. Variation in selection may occur if predators only learn particular colour pattern components rather than the entire signal. Here, we used a nudibranch mollusc, Goniobranchus splendidus , which exhibits a conspicuous red spot/white body/yellow rim colour pattern, to test this hypothesis. We first demonstrated that secondary metabolites stored within the nudibranch were unpalatable to a marine organism. Using pattern analysis, we demonstrated that the yellow rim remained invariable within and between populations; however, red spots varied significantly in both colour and pattern. In behavioural experiments, a potential fish predator, Rhinecanthus aculeatus , used the presence of the yellow rims to recognize and avoid warning signals. Yellow rims remained stable in the presence of high genetic divergence among populations. We therefore suggest that how predators learn warning signals may cause stabilizing selection on individual colour pattern elements, and will thus have important implications on the evolution of warning signals.

Initial evolution of warning coloration: comments on the novel world method

2000 ◽  
Vol 60 (1) ◽  
pp. F1-F2 ◽  
Author(s):  
Rauno V. Alatalo ◽  
Johanna Mappes
Keyword(s):  
The Novel ◽  
Warning Coloration ◽  
Initial Evolution

scholarly journals Early warning signals of regime shifts in coupled human–environment systems

2016 ◽  
Vol 113 (51) ◽  
pp. 14560-14567 ◽  
Author(s):  
Chris T. Bauch ◽  
Ram Sigdel ◽  
Joe Pharaon ◽  
Madhur Anand
Keyword(s):  
Early Warning ◽  
Warning Signal ◽  
Regime Shifts ◽  
Dynamical Regime ◽  
Ecological Data ◽  
Warning Signals ◽  
Early Warning Signals ◽  
Human Environment ◽  
Environment Model ◽  
External Conditions

In complex systems, a critical transition is a shift in a system’s dynamical regime from its current state to a strongly contrasting state as external conditions move beyond a tipping point. These transitions are often preceded by characteristic early warning signals such as increased system variability. However, early warning signals in complex, coupled human–environment systems (HESs) remain little studied. Here, we compare critical transitions and their early warning signals in a coupled HES model to an equivalent environment model uncoupled from the human system. We parameterize the HES model, using social and ecological data from old-growth forests in Oregon. We find that the coupled HES exhibits a richer variety of dynamics and regime shifts than the uncoupled environment system. Moreover, the early warning signals in the coupled HES can be ambiguous, heralding either an era of ecosystem conservationism or collapse of both forest ecosystems and conservationism. The presence of human feedback in the coupled HES can also mitigate the early warning signal, making it more difficult to detect the oncoming regime shift. We furthermore show how the coupled HES can be “doomed to criticality”: Strategic human interactions cause the system to remain perpetually in the vicinity of a collapse threshold, as humans become complacent when the resource seems protected but respond rapidly when it is under immediate threat. We conclude that the opportunities, benefits, and challenges of modeling regime shifts and early warning signals in coupled HESs merit further research.

scholarly journals Visual Warning Signals Optimized for Human Perception: What the Eye Sees Fastest

2005 ◽  
Vol 2 (1) ◽  
pp. 45-52 ◽  
Author(s):  
B. L. Gros ◽  
D. S. Greenhouse ◽  
T. E. Cohn
Keyword(s):  
Human Perception ◽  
Warning Signal ◽  
Sensitivity Function ◽  
Visual Signals ◽  
Temporal Contrast ◽  
Warning Signals ◽  
Moving Stimuli ◽  
Classic Problem ◽  
Speed Advantage ◽  
Spatio Temporal

This study aimed to answer the question of how to design a visual warning signal that is most easily seen and produces the quickest reaction time. This is a classic problem of bionic optimization—if one knows the properties of the receiver one can most easily find a suitable solution. Because the peak of the spatio-temporal contrast sensitivity function of the human visual system occurs at non-zero spatial and temporal frequencies, it is likely that movement enhances the detectability of threshold visual signals. Earlier studies employing extended drifting sinewave gratings bear out this prediction. We have studied the ability of human observers to detect threshold visual signals for both moving and stationary stimuli. We used discrete, localized signals such as might be employed in aerospace or automotive warning signal displays. Moving stimuli show a superior detectability to non-moving stimuli of the same integrated energy. Moving stimuli at threshold detectability are seen faster than non-moving threshold stimuli. Under some conditions the speed advantage is over 0.25 seconds. Similar advantages have also been shown to occur for suprathreshold signals.

scholarly journals Effects of acoustic warning signal intensity in the control of visuospatial interference

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Paola Cappucci ◽  
Ángel Correa ◽  
Rico Fisher ◽  
Torsten Schubert ◽  
Juan Lupiáñez
Keyword(s):  
Warning Signal ◽  
Attentional Focus ◽  
Warning Signals ◽  
Stimulus Response ◽  
Spatial Stimulus ◽  
Spatial Attributes ◽  
Task Irrelevant ◽  
Open Question ◽  
The Impact ◽  
Spatial Stroop

AbstractPrevious studies have reported increased interference when a task-irrelevant acoustic warning signal preceded the target presentation in cognitive tasks. However, the alerting-congruence interaction was mostly observed for tasks measuring Flanker and Simon interferences but not for Stroop conflict. These findings led to the assumption that warning signals widen the attentional focus and facilitate the processing of irrelevant spatial characteristics. However, it is not clear whether these effects are because of the temporal information provided by the warning signal or because of their alerting effects. Based on these findings, and on the open question about the nature of the warning signal intervention on visuospatial interferences, we decided to test the impact of the warning signal on the processing of irrelevant spatial features, by using a procedure suitable for measuring both Simon and spatial Stroop interferences. We also manipulated the intensity of the warning signal to study the effect of the task-irrelevant characteristics of warning signals in visuospatial interferences. For the Simon conflict, results demonstrated an increased interference provoked by the presence (Experiment 1) and intensity (Experiment 2) of warning signals. In contrast, neither the presence nor the intensity of warning signals affected the spatial Stroop interference. Overall, these findings suggest that the impact of warning signals primarily depends on the processing of irrelevant spatial attributes and on the type of conflict (e.g., spatial stimulus-response interference in Simon vs. stimulus-stimulus interference in spatial Stroop). In general, acoustic warning signals facilitate the automatic response activation, but their modulatory effect depends on the task setting involved.

scholarly journals Predator perception and the interrelation between different forms of protective coloration

2007 ◽  
Vol 274 (1617) ◽  
pp. 1457-1464 ◽  
Author(s):  
Martin Stevens
Keyword(s):  
Visual Perception ◽  
Warning Coloration ◽  
Protective Coloration ◽  
Disruptive Coloration ◽  
Risk Of Predation ◽  
Motion Camouflage ◽  
Future Work

Animals possess a range of defensive markings to reduce the risk of predation, including warning colours, camouflage, eyespots and mimicry. These different strategies are frequently considered independently, and with little regard towards predator vision, even though they may be linked in various ways and can be fully understood only in terms of predator perception. For example, camouflage and warning coloration need not be mutually exclusive, and may frequently exploit similar features of visual perception. This paper outlines how different forms of protective markings can be understood from predator perception and illustrates how this is fundamental in determining the mechanisms underlying, and the interrelation between, different strategies. Suggestions are made for future work, and potential mechanisms discussed in relation to various forms of defensive coloration, including disruptive coloration, eyespots, dazzle markings, motion camouflage, aposematism and mimicry.

A New Foreperiod Effect on Intertrial Phase Coherence. Part I: Existence and Behavioral Relevance

2018 ◽  
Vol 30 (9) ◽  
pp. 2348-2383 ◽  
Author(s):  
Joaquin Rapela ◽  
Marissa Westerfield ◽  
Jeanne Townsend
Keyword(s):  
Reaction Time ◽  
Warning Signal ◽  
Phase Coherence ◽  
Warning Signals ◽  
Temporal Expectation ◽  
Relevant Effect ◽  
Phase Alignment ◽  
Multiple Trials ◽  
Trial Basis ◽  
Eeg Recordings

This letter makes scientific and methodological contributions. Scientifically, it demonstrates a new and behaviorally relevant effect of temporal expectation on the phase coherence of the electroencephalogram (EEG). Methodologically, it introduces novel methods to characterize EEG recordings at the single-trial level. Expecting events in time can lead to more efficient behavior. A remarkable finding in the study of temporal expectation is the foreperiod effect on reaction time, that is, the influence on reaction time of the delay between a warning signal and a succeeding imperative stimulus to which subjects are instructed to respond as quickly as possible. Here we study a new foreperiod effect in an audiovisual attention-shifting oddball task in which attention-shift cues directed the attention of subjects to impendent deviant stimuli of a given modality and therefore acted as warning signals for these deviants. Standard stimuli, to which subjects did not respond, were interspersed between warning signals and deviants. We hypothesized that foreperiod durations modulated intertrial phase coherence (ITPC, the degree of phase alignment across multiple trials) evoked by behaviorally irrelevant standards and that these modulations are behaviorally meaningful. Using averaged data, we first observed that ITPC evoked by standards closer to the warning signal was significantly different from that evoked by standards further away from it, establishing a new foreperiod effect on ITPC evoked by standards. We call this effect the standard foreperiod (SFP) effect on ITPC. We reasoned that if the SFP influences ITPC evoked by standards, it should be possible to decode the former from the latter on a trial-by-trial basis. We were able to do so showing that this effect can be observed in single trials. We demonstrated the behavioral relevance of the SFP effect on ITPC by showing significant correlations between its strength and subjects' behavioral performance.

Warning Signals Induce Automatic EMG Activations and Proactive Volitional Inhibition: Evidence From Analysis of Error Distribution in Simple RT

2008 ◽  
Vol 99 (3) ◽  
pp. 1572-1578 ◽  
Author(s):  
Philippe Boulinguez ◽  
Magali Jaffard ◽  
Lionel Granjon ◽  
Abdelrhani Benraiss
Keyword(s):  
Simple Reaction Time ◽  
Warning Signal ◽  
Proactive Inhibition ◽  
Error Distribution ◽  
False Alarms ◽  
Warning Stimulus ◽  
Distribution Analysis ◽  
Warning Signals ◽  
Simple Rt ◽  
Analysis Of Error

Typical simple reaction-time (RT) paradigms usually include a warning signal followed by a variable foreperiod before the presentation of a reaction stimulus. Most current interpretations suggest that the warning stimulus alerts the organism and so results in faster processing of either the sensory or motor components of the task. In this study, electromyography (EMG) was used to detect both covert and overt motor errors in a simple warned RT task. Results show that warning signals may trigger automatic motor activations that are likely to cause false alarms. Distribution analysis reveals that 77% of all errors detected with EMG are erroneous responses to the warning signal. Accordingly, we propose that movement triggering needs to be temporarily inhibited before the stimulus to prevent premature responses during the foreperiod. This proactive inhibition would be responsible for a paradoxical increase in RT for conditions with short foreperiods compared with control conditions in which no warning signal is presented. These results call for a reassessment of the theoretical framework used to interpret the effects of warning signals.

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