Aposematism

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Michael P Speed - One of the best experts on this subject based on the ideXlab platform.

  • "Parasite-induced Aposematism" protects entomopathogenic nematode parasites against invertebrate enemies
    Behavioral Ecology, 2015
    Co-Authors: Rebecca S. Jones, Andy Fenton, Michael P Speed
    Abstract:

    Aposematism is a well-known strategy in which prey defend themselves from predation by pairing defenses such as toxins, with warning signals that are often visually conspicuous color patterns. Here, we examine the possibility that Aposematism can be induced in a host by colonies of infectious parasites in order to protect the parasites from the consequences of attacks on the host. Earlier studies show that avian predators are reluctant to feed on carcasses of host prey that are infected with the entomopathogenic nematode, Heterorhabditis bacteriophora. As the age of infection increases, the parasites kill and preserve the host and subsequently cause its color to change, becoming bright pink then red. Nematode colonies in dead hosts may also be vulnerable, however, to nocturnally active foragers that do not use vision in prey detection. Here, then we test a novel hypothesis that the nematode parasites also produce a warning odor, which functions to repel nocturnally active predators (in this case, the beetle Pterostichus madidus). We show that beetles decrease their feeding on infected insect prey as the age of infection increases and that olfactory cues associated with the infections are effective mechanisms for deterring beetle predation, even at very early stages of infection. We propose that "parasite-induced Aposematism" from the nematodes serves to replace the antipredator defenses of the recently killed host. Because sessile carcasses are exposed to a greater range of predators than the live hosts, several alternative defense mechanisms are required to protect the colony, hence aposematic signals are likely diverse in such "parasite-induced Aposematism."

  • Florivory as an Opportunity Benefit of Aposematism
    The American Naturalist, 2015
    Co-Authors: Andrew D. Higginson, Michael P Speed, Graeme D Ruxton
    Abstract:

    Inconspicuous prey pay a cost of reduced feeding opportunities. Flowers are highly nutritious but are positioned where prey would be apparent to predators and often contain toxins to reduce consumption. However, many herbivores are specialized to subvert these defenses by retaining toxins for their own use. Here, we present a model of the growth and life history of a small herbivore that can feed on leaves or flowers during its development and can change its primary defense against visual predators between crypsis and warning coloration. When herbivores can retain plant toxins, their fitness is greatly increased when they are aposematic and can consume flowers. Thus, toxin sequestration leading to Aposematism may enable a significant opportunity benefit for florivory. Florivory by cryptic herbivores is predicted when toxins are very potent but are at high concentration only in flowers and not in leaves. Herbivores should usually switch to eating flowers only when large and in most conditions should switch simultaneously from crypsis to Aposematism. Our results suggest that florivory should be widespread in later instars of small aposematic herbivores and should be associated with ontogenic color change. Florivory is likely to play an underappreciated role in herbivorous insect life histories and host plant reproductive success.

  • Are aposematic signals honest? A review
    Journal of Evolutionary Biology, 2015
    Co-Authors: Kyle Summers, Michael P Speed, Jonathan D. Blount, Adam M. M. Stuckert
    Abstract:

    We explore the relevance of honest signalling theory to the evolution of Aposematism. We begin with a general consideration of models of signal stability, with a focus on the Zahavian costly signalling framework. Next, we review early models of signalling in the context of Aposematism (some that are consistent and some inconsistent with costly honest signalling). We focus on controversies surrounding the idea that aposematic signals are handicaps in a Zahavian framework. Then, we discuss how the alignment of interests between signaller and predator influences the evolution of Aposematism, highlight the distinction between qualitative and quantitative honesty and review theory and research relevant to these categories. We also review recent theoretical treatments of the evolution of Aposematism that have focused on honest signalling as well as empirical research on a variety of organisms, including invertebrates and frogs. Finally, we discuss future directions for empirical and theoretical research in this area.

  • The effect of metapopulation dynamics on the survival and spread of a novel, conspicuous prey
    Journal of Theoretical Biology, 2010
    Co-Authors: Thomas J. Lee, Michael P Speed
    Abstract:

    Animals that deploy chemical defences against predators often signal their unprofitability using bright colouration. This pairing of toxicity and conspicuous patterning is known as Aposematism.

  • The effect of metapopulation dynamics on the survival and spread of a novel, conspicuous prey
    Journal of Theoretical Biology, 2010
    Co-Authors: Thomas J. Lee, Michael P Speed
    Abstract:

    Animals that deploy chemical defences against predators often signal their unprofitability using bright colouration. This pairing of toxicity and conspicuous patterning is known as Aposematism. Explaining the evolution and spread of aposematic traits in previously cryptic species has been the focus of much empirical and theoretical work over the last two decades. Existing research concerning the initial evolution of Aposematism does not however properly consider that many aposematic species (such as members of the hymenoptera, the lepidoptera, and amphibia) are highly mobile. We argue in this paper that the evolution of aposematic displays is therefore often best understood within a metapopulation framework; hence in this paper we present the first explicit metapopulation model of the evolution of Aposematism. Our most general finding is that migration tends to reduce the probability that an aposematic prey can increase from rarity and spread across a large population. Hence, the best case scenarios for the spread of Aposematism required fixation of the aposematic form in one or more isolated sub-habitats prior to some event which subsequently enabled migration. We observed that changes in frequency of new aposematic forms within source habitats are likely to be nonmonotonic. First, aposematic prey tend to decline in frequency as they migrate outwards from the source habitat to neighbouring sink habitats, but subsequently they increase in relative abundance in the source, as the descendents of earlier migrants migrate back from newly converted sub-populations. This pattern of initial loss and subsequent gain between new source and neighbouring sink habitats is then repeated as the aposematic form spreads via a moving cline.

Graeme D Ruxton - One of the best experts on this subject based on the ideXlab platform.

  • Aposematism: Unpacking the Defences.
    Trends in Ecology and Evolution, 2019
    Co-Authors: Tim Caro, Graeme D Ruxton
    Abstract:

    Aposematic coloration is commonly considered to signal unpalatability, yet animals advertise malodour, spines, and weaponry as well as toxins, some of which can be seen at a distance whereas others are hidden from predators. Separating defences into overt and covert categories in this way and whether they act before, during contact, or following ingestion generates new insights into the evolution of Aposematism. Signals drawing attention to overt defences are difficult to fake whereas signals advertising covert defences can deceive would-be predators, and those acting later in the predatory sequence are more likely to be dishonest. These two orthogonal defence categorizations help to frame where dishonest signalling occurs in nature, set limits on deception by dishonest Batesian mimics, and prompt new questions.

  • Florivory as an Opportunity Benefit of Aposematism
    The American Naturalist, 2015
    Co-Authors: Andrew D. Higginson, Michael P Speed, Graeme D Ruxton
    Abstract:

    Inconspicuous prey pay a cost of reduced feeding opportunities. Flowers are highly nutritious but are positioned where prey would be apparent to predators and often contain toxins to reduce consumption. However, many herbivores are specialized to subvert these defenses by retaining toxins for their own use. Here, we present a model of the growth and life history of a small herbivore that can feed on leaves or flowers during its development and can change its primary defense against visual predators between crypsis and warning coloration. When herbivores can retain plant toxins, their fitness is greatly increased when they are aposematic and can consume flowers. Thus, toxin sequestration leading to Aposematism may enable a significant opportunity benefit for florivory. Florivory by cryptic herbivores is predicted when toxins are very potent but are at high concentration only in flowers and not in leaves. Herbivores should usually switch to eating flowers only when large and in most conditions should switch simultaneously from crypsis to Aposematism. Our results suggest that florivory should be widespread in later instars of small aposematic herbivores and should be associated with ontogenic color change. Florivory is likely to play an underappreciated role in herbivorous insect life histories and host plant reproductive success.

  • protection by association evidence for aposematic commensalism
    Biological Journal of The Linnean Society, 2012
    Co-Authors: Leoni De Wert, Kevin Mahon, Graeme D Ruxton
    Abstract:

    Aposematism is a well known and widely used strategy for reducing predation by conspicuous signalling of unprofitability. However, the increased conspicuousness could make this strategy costly if there are no secondary defences to back the signal up. This has made the elucidation of the evolutionary mechanisms for Aposematism and that of the closely-related Batesian and Mullerian mimicry difficult. The present study aims to test whether cryptic and nondefended prey could reduce their predation risk by grouping with aposematic and defended prey. To do this, we used groups of artificial baits that were either cryptic and palatable or conspicuous and unpalatable, along with the corresponding control treatments. These were then presented in mixed and homogeneous treatment groups within a field setting and the local wild bird assemblage was allowed to select and remove baits at will. The results obtained show that undefended non-aposematic prey can benefit by grouping with aposematic prey, with no evidence that predation rates for aposematic prey were adversely affected by this association. These results provide insights into the evolution of Batesian mimicry. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106, 81–89.

  • Linking the evolution and form of warning coloration in nature
    Proceedings of The Royal Society B: Biological Sciences, 2011
    Co-Authors: Martin Stevens, Graeme D Ruxton
    Abstract:

    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.

  • THE DUAL BENEFITS OF Aposematism: PREDATOR AVOIDANCE AND ENHANCED RESOURCE COLLECTION
    Evolution, 2009
    Co-Authors: Michael P Speed, Michael A. Brockhurst, Graeme D Ruxton
    Abstract:

    Theories of Aposematism often focus on the idea that warning displays evolve because they work as effective signals to predators. Here, we argue that Aposematism may instead evolve because, by enhancing protection, it enables animals to become more exposed and thereby gain resource-gathering benefits, for example, through a wider foraging niche. Frequency-dependent barriers (caused by enhanced conspicuousness relative to other prey and low levels of predator education) are generally assumed to make the evolution of Aposematism particularly challenging. Using a deterministic, evolutionary model we show that aposematic display could evolve relatively easily if it enabled prey to move more freely around their environments, or become exposed in some other manner that provides fitness benefits unrelated to predation risk. Furthermore, the model shows that the traits of aposematic conspicuousness and behavior which lead to raised exposure positively affect each other, so that the optimal level of both tends to increase when the traits exist together, compared to when they exist in isolation. We discuss the ecological and evolutionary consequences of Aposematism. One conclusion is that Aposematism could be a key evolutionary innovation, because by widening habitat use it may promote adaptive radiation as a byproduct of enhanced ecological opportunity.

Andreas Rudh - One of the best experts on this subject based on the ideXlab platform.

  • COARSE DARK PATTERNING FUNCTIONALLY CONSTRAINS ADAPTIVE SHIFTS FROM Aposematism TO CRYPSIS IN STRAWBERRY POISON FROGS
    Evolution, 2014
    Co-Authors: Anna Qvarnström, Andreas Rudh, Anders Ödeen, Torkel Edström, Hanne Løvlie, Birgitta S Tullberg
    Abstract:

    Ecological specialization often requires tight coevolution of several traits, which may constrain future evolutionary pathways and make species more prone to extinction. Aposematism and crypsis represent two specialized adaptations to avoid predation. We tested whether the combined effects of color and pattern on prey conspicuousness functionally constrain or facilitate shifts between these two adaptations. We combined data from 17 natural populations of strawberry poison frogs, Oophaga pumilio with an experimental approach using digitalized images of frogs and chickens as predators. We show that bright coloration often co-occurs with coarse patterning among the natural populations. Dull green frogs with coarse patterning are rare in nature but in the experiment they were as easily detected as bright red frogs suggesting that this trait combination represents a transient evolutionary state toward Aposematism. Hence, a gain of either bright color or coarse patterning leads to conspicuousness, but a transition back to crypsis would be functionally constrained in populations with both bright color and coarse patterning by requiring simultaneous changes in two traits. Thus, populations (or species) signaling Aposematism by conspicuous color should be less likely to face an evolutionary dead end and more likely to radiate than populations with both conspicuous color and coarse patterning.

  • Loss of conspicuous coloration has co-evolved with decreased body size in populations of poison dart frogs
    Evolutionary Ecology, 2013
    Co-Authors: Andreas Rudh
    Abstract:

    Larger signal size is known to facilitate the learning process of predators to warning signals. Further, smaller objects are generally harder to detect than large, which suggests that smaller sized prey are less likely to benefit from an aposematic strategy compared to crypsis. However, whether body size changes in concert with shifts between crypsis and Aposematism in natural populations, remains largely unexplored. I tested whether body size was larger in visually conspicuous population than in cryptic populations among recently diverged populations of the Strawberry Poison frog, Oophaga pumilio. By analysing spectral reflectance and body size data from individuals from 18 discrete populations I found a larger mean body size in conspicuous populations, which was confirmed by an analysis of a subset of 12 populations accounting for phylogenetic history. This shows that the loss of conspicuous colour likely co-evolved repeatedly with a decrease in body size. Thus, selection on body size may influence evolutionary shifts between Aposematism and crypsis and vice versa.

  • Pattern coarseness affects detectability of dull but not of conspicuously coloured poison frogs by an avian predator - implications for evolutionary transitions between Aposematism and crypsis
    2012
    Co-Authors: Andreas Rudh, Birgitta S Tullberg, Anders Ödeen, Torkel Edström, Hanne Løvlie, Anna Qvarnström
    Abstract:

    Pattern coarseness affects detectability of dull but not of conspicuously coloured poison frogs by an avian predator - implications for evolutionary transitions between Aposematism and crypsis

  • Aposematism, Crypsis and Population Differentiation in the Strawberry Poison Frog
    2012
    Co-Authors: Andreas Rudh
    Abstract:

    Evolutionary transitions between the two major predator avoidance strategies Aposematism and crypsis are expected to be associated with changes in many important traits of animals. However, empiric ...

Laurie J. Vitt - One of the best experts on this subject based on the ideXlab platform.

  • conspicuousness and vestigial escape behaviour by two dendrobatid frogs dendrobates auratus and oophaga pumilio
    Behaviour, 2009
    Co-Authors: William E. Cooper, Janalee P. Caldwell, Laurie J. Vitt
    Abstract:

    Aposematic prey are thought to move slowly and openly near predators, but exhibit reduced escape behaviour. We studied conspicuousness and escape by aposematic poison frogs ( Dendrobates auratus and Oophaga pumilio ). In circles of leaf litter, observers detected poison frogs quickly. Flight initiation distance (FID, predator-prey distance when escape begins) increases with approach speed in non-cryptic palatable prey, but not for frogs in clearings, which permitted close approach. On trails frogs moved slowly into forest and FID in D. auratus increased with approach speed. Distance from cover and handling exposing predators to distastefulness may account for greater reliance on Aposematism in clearings. We observed responses to a simulated predator (stick with painted face) in three conditions: not approached, approached, and touched. Latency to hop and time to exit circles decreased and exit from circles was directed further away from the approach path in the order not approached, approached, touched. Oophaga pumilio changed directions less when approached than not; many exhibited no escape behaviour. Aposematic dendrobatids move slowly near predators, but retain risk-assessment mechanisms due to occasional predation. Differences in escape between dendrobatids and palatable Craugastor frogs suggest that dendrobatid defensive behavior may have been molded to maximize the effectiveness of Aposematism.

William E. Cooper - One of the best experts on this subject based on the ideXlab platform.

  • conspicuousness and vestigial escape behaviour by two dendrobatid frogs dendrobates auratus and oophaga pumilio
    Behaviour, 2009
    Co-Authors: William E. Cooper, Janalee P. Caldwell, Laurie J. Vitt
    Abstract:

    Aposematic prey are thought to move slowly and openly near predators, but exhibit reduced escape behaviour. We studied conspicuousness and escape by aposematic poison frogs ( Dendrobates auratus and Oophaga pumilio ). In circles of leaf litter, observers detected poison frogs quickly. Flight initiation distance (FID, predator-prey distance when escape begins) increases with approach speed in non-cryptic palatable prey, but not for frogs in clearings, which permitted close approach. On trails frogs moved slowly into forest and FID in D. auratus increased with approach speed. Distance from cover and handling exposing predators to distastefulness may account for greater reliance on Aposematism in clearings. We observed responses to a simulated predator (stick with painted face) in three conditions: not approached, approached, and touched. Latency to hop and time to exit circles decreased and exit from circles was directed further away from the approach path in the order not approached, approached, touched. Oophaga pumilio changed directions less when approached than not; many exhibited no escape behaviour. Aposematic dendrobatids move slowly near predators, but retain risk-assessment mechanisms due to occasional predation. Differences in escape between dendrobatids and palatable Craugastor frogs suggest that dendrobatid defensive behavior may have been molded to maximize the effectiveness of Aposematism.