Mimicry among Unequally Defended Prey Should Be Mutualistic When Predators Sample Optimally

Abstract

Understanding the conditions under which moderately defended prey evolve to resemble better-defended prey and whether this mimicry is parasitic (quasi-Batesian) or mutualistic (Müllerian) is central to our understanding of warning signals. Models of predator learning generally predict quasi-Batesian relationships. However, predators' attack decisions are based not only on learning alone but also on the potential future rewards. We identify the optimal sampling strategy of predators capable of classifying prey into different profitability categories and contrast the implications of these rules for mimicry evolution with a classical Pavlovian model based on conditioning. In both cases, the presence of moderately unprofitable mimics causes an increase in overall consumption. However, in the case of the optimal sampling strategy, this increase in consumption is typically outweighed by the increase in overall density of prey sharing the model appearance (a dilution effect), causing a decrease in mortality. It suggests that if predators forage efficiently to maximize their long-term payoff, genuine quasi-Batesian mimicry should be rare, which may explain the scarcity of evidence for it in nature. Nevertheless, we show that when moderately defended mimics are profitable to attack by hungry predators, then they can be parasitic on their models, just as classical Batesian mimics are.

Not all toxic butterflies are toxic: high intra‐ and interspecific variation in sequestration in subtropical swallowtails

“…Since there is no individual survival benefit in being toxic, some individuals of a population produce little or nothing of the costly defense (the automimics). These individuals can still get protection because other members of the same population that are similar in appearance are defended and deter predators (Brower et al 1970, 1975, Tuskes and Brower 1978, Daly et al 2012, Aubier et al 2017. The potential tradeoff found in our studied system in Iguaz u between sequestering chemical defenses and larval survivorship might be explained by automimicry.…”

“…, Aubier et al. ). The potential tradeoff found in our studied system in Iguazú between sequestering chemical defenses and larval survivorship might be explained by automimicry.…”

“…However, due to the highly unpredictable mimetic environment, the existence of such phenomenon in the butterfly species studied herein is unlikely, and Müllerian mimicry seems more plausible (Aubier et al. ). Since there are multiple possible models exhibiting a range of AA concentrations, unlike B. philenor in North America, distasteful troidine individuals that share similar warning signals and the mutual benefit of being avoided by common predators might produce a Müllerian mimicry complex rather than a Batesian one.…”

“…This aposematic coloration has been invoked to explain mimicry complexes where one species is toxic and the other is not (in the case of Batesian mimicry), or both species are toxic (in the case of Mullerian mimicry), physically resemble each other, thereby gaining protection against predators (Brower , Mallet and Joron , see also Aubier et al. ).…”

“…Butterflies that sequester toxic compounds from their host plant often exhibit aposematic or warning coloration to visually advertise their unpalatability to natural enemies. This aposematic coloration has been invoked to explain mimicry complexes where one species is toxic and the other is not (in the case of Batesian mimicry), or both species are toxic (in the case of Mullerian mimicry), physically resemble each other, thereby gaining protection against predators (Brower 1958, Mallet andJoron 1999, see also Aubier et al 2017).…”