The dual benefits of aposematism: Predator avoidance and enhanced resource collection

School of Biological Sciences, Biosciences, University of Liverpool, Crown Street, Liverpool L69 7ZB, United Kingdom.
Evolution (Impact Factor: 4.61). 06/2010; 64(6):1622-33. DOI: 10.1111/j.1558-5646.2009.00931.x
Source: PubMed


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.

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Available from: Michael P Speed, Jan 07, 2014
    • "Just as individual traits should be examined as components of integrated phenotypes, individual selective influence (e.g., mate choice, heterospecific interactions) integrates to form an organism's overall selective environment. If aposematism confers additional benefits to protection from predators, such as access to more resources as a result of dominant advantage not only over conspecifics but also over competing heterospecifics, these benefits could likely influence character diversification (Speed et al. 2010). In the case of ecological consequences, negative interactions such as heterospecific aggression, can affect resource and habitat use and may therefore influence community structure (reviewed by Peiman and Robinson 2010). "
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    ABSTRACT: Intraspecific morphological variation may correspond to behavioral variation that helps determine the nature of species interactions. Color variation among populations of variably toxic organisms has been shown to associate with alternative anti-predator behaviors. However, the effects of these alternative behavioral tendencies on the outcomes of interspecific interactions other than predator–prey remain largely unexplored. We investigated how coloration and body size variation in Oophaga pumilio, one of the most phenotypically diverse amphibians known, associated with territorial aggressiveness and how this association influenced the outcome of agonistic male–male interactions with conspecifics and heterospecifics of two sympatric species (Andinobates claudiae and Phyllobates lugubris). Irrespective of body size, resident frogs from more conspicuous, red-colored O. pumilio populations responded to same-morph conspecifics and P. lugubris more quickly and exhibited more aggressive behaviors and more energetically expensive behaviors than resident frogs from green populations under these same treatments. Furthermore, red-colored resident frogs dominated most of the interactions in which they were involved, whereas green residents dominated only a few of the interactions, despite their status as residents. Because conspecific and heterospecific intruders did not behave more aggressively toward red resident frogs, aggressiveness of red residents does not appear to be a response to higher aggression being directed toward them. These results suggest that coloration in O. pumilio is a good indicator of aggressiveness that associates with the outcome of intraspecific and some interspecific behavioral male–male interactions, providing support for a positive association among anti-predator traits, agonistic behavior, and dominance in both intraspecific and interspecific, intraguild interactions.
    No preview · Article · Nov 2015 · Behavioral Ecology and Sociobiology
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    • "Foraging theory is often concerned with opportunity costs associated with different options (Winterhalder 1983; Nonacs 2001; Eccard and Liesenjohann 2014). Florivory may provide an opportunity benefit of aposematism (Stevens and Ruxton 2013) through enhanced resource collection , which is underappreciated in the understanding of the prevalence and evolution of aposematism (Speed et al. 2010). Aposematism is often not tenable for small animals because their warning signal is weak and individually they expose predators to small, ineffective toxin doses (Forsman and Merilaita 1999; Mänd et al. 2007; Remmel and Tammaru 2011). "
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    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.
    Full-text · Article · Oct 2015 · The American Naturalist
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    • "It has been suggested recently that aposematic species may have advantages over cryptic ones during the exploitation of newly available resources (Speed et al., 2010). That is because aposematic colouration grants individuals the protection to freely move around and explore, for example, new habitats as local predators would quickly learn that they are unpalatable (Speed et al., 2010). If prey can survive from the attack (Skelhorn and Rowe, 2006), or predators are neophobic (i.e., refuse to attack novel prey (Marples and Kelly, 1999)), or they have inherited tendencies to avoid such prey (Lindström et al., 1999a), these can indeed enhance the invasion success. "
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    ABSTRACT: The striking colour-pattern variation of some aposematic species is paradoxical because selection by predators is expected to favour signal uniformity. Although the mechanisms allowing for the maintenance of such variation are not well understood, possible explanations include both non-adaptive processes like drift and gene flow; and adaptive processes, such as an interaction between natural and sexual selection, spatial and temporal variation in selection, a link between behaviour or other fitness-related traits and phenotype, and predators’ ability to generalise among different signals. Here we test whether warning-signal polymorphisms, such as that of dyeing poison frogs (Dendrobates tinctorius), could be maintained by differences in detectability among morphs. We did experiments in the wild using wax models with different aposematic colour patterns vs. cryptic ones, and examined the attack rates by wild predators over time. We also tested the detectability of different aposematic morphs by ‘human predators’ under different light environments. We found that cryptic frog models were attacked more than aposematic models, but there were no differences in bird attack rates towards the different aposematic morphs. However, we found that detectability of different morphs depends both on predator experience and light environment. We suggest that the interaction between differential detectability and signal efficiency among morphs in different light conditions could be a mechanism aiding to the maintenance of warning-signal polymorphisms. Our results highlight the importance of considering the light environment at which predators have their first encounters with aposematic prey for future studies on predation in the wild.
    Full-text · Article · Aug 2014 · Behavioural Processes
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