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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.

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.

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, Torkel Edström, Anders Ödeen, 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, Torkel Edström, Anders Ödeen, 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