The Dual Benefits of Aposematism: Predator Avoidance and Enhanced Resource Collection

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.K E Y W O R D S : Aposematism, key innovation, life history, niche, predator.

Phenotypic integration emerges from aposematism and scale in poison frogs

“…In the pairwise analyses (Table S2), we found significant correlations (P < 0.01) between aposematism, diet specialization, body mass, and two measures of aerobic capacity (AMR and scope). These results suggest that the appearance of a phylogenetic correlation between aposematism and aerobic capacity preceded enhanced resource gathering, which in turn promoted diet specialization (8). An alternative explanation is that diet specialization preceded the origin of higher aerobic capacity, assuming prey are a patchy resource (30), with aposematism evolving as a defense against predators.…”

“…Two alternative hypotheses characterize the sequence of adaptations leading to the integration of aposematism and scale in poison frogs. First, as a preexisting predator deterrent, aposematism allowed individuals to increase resource-gathering abilities in the form of high aerobic capacity and diet specialization (8). Under this alternative, aposematism initially linked chemical defense with a generalist diet; however, this diet must have included some alkaloidbearing arthropods.…”

“…In aposematism, predators associate conspicuous prey with an unprofitable meal and refrain from attack (7). Thus, defended, the prey may expand its own foraging capabilities (8). The evolution of aposematism is complex for at least four reasons.…”

Linking the evolution and form of warning coloration in nature

“…These opportunity costs are not generally considered to apply to aposematism. Speed et al [56] make the important point that greater freedom to exploit resources may be an important selective pressure encouraging evolution of aposematism. We would also argue that aposematism might influence other aspects of life-history through this mechanism.…”

Antipredator defenses predict diversification rates

“…This became known as the "escape-and-radiate" hypothesis (2). Similarly, it has been suggested that bright coloration can reduce the constraints of hiding, enabling niche expansion and promoting diversification in animal prey (3,4). The escape-and-radiate hypothesis is influential in the adaptive radiation literature (2,5,6) but has been tested surprisingly rarely (6)(7)(8).…”