Prey community structure affects how predators select for Müllerian mimicry

Abstract

Müllerian mimicry describes the close resemblance between aposematic prey species; it is thought to be beneficial because sharing a warning signal decreases the mortality caused by sampling by inexperienced predators learning to avoid the signal. It has been hypothesized that selection for mimicry is strongest in multi-species prey communities where predators are more prone to misidentify the prey than in simple communities. In this study, wild great tits (Parus major) foraged from either simple (few prey appearances) or complex (several prey appearances) artificial prey communities where a specific model prey was always present. Owing to slower learning, the model did suffer higher mortality in complex communities when the birds were inexperienced. However, in a subsequent generalization test to potential mimics of the model prey (a continuum of signal accuracy), only birds that had foraged from simple communities selected against inaccurate mimics. Therefore, accurate mimicry is more likely to evolve in simple communities even though predator avoidance learning is slower in complex communities. For mimicry to evolve, prey species must have a common predator; the effective community consists of the predator's diet. In diverse environments, the limited diets of specialist predators could create 'simple community pockets' where accurate mimicry is selected for.

Influences of geographic differentiation in the forewing warning signal of the wood tiger moth in Alaska

“…A limited flying season for lepidopteran species likely reduces the time in which tight relationships between predator and prey can develop when predators initially learn to avoid signals, leading to greater generalization by predators. Relationships between predators and prey may be more specialized in the tropics, which could increase the degree of signal homogeneity in a population (discussed in Ihalainen et al 2012). If predators in northern areas generalize more widely compared to predators in tropical areas, it may permit more intraspecific variation in warning signal appearance for aposematic species occurring at higher latitudes.…”

“…One additional explanation for why positive FDS may not always be found is that predators may generalize their avoidance of warning signals more broadly. Generalized avoidance of warning signals should result in weakened positive FDS (Ihalainen et al 2012). A recent on Oophaga histrionica found some evidence to suggest predators generalized their avoidance to warning signals that differed in color and pattern of foreign warning signals (Amézquita et al 2013).…”

Effect of maternal predator exposure on the ability of stickleback offspring to generalize a learned colour–reward association

“…For example, learning about one predator can improve antipredator behaviour and survival when exposed to a different predator (Brown et al, 2011; Ferrari, Brown, Messier, & Chivers, 2009; Ferrari, Gonzalo, Messier, & Chivers, 2007; Griffin, Evans, & Blumstein, 2001; Mitchell, McCormick, Chivers, & Ferrari, 2013). Similarly, learning about particular prey items can improve foraging performance (or avoidance) when exposed to novel items (Ihalainen, Rowland, Speed, Ruxton, & Mappes, 2012; Marples, Quinlan, Thomas, & Kelly, 2007; Svádová et al, 2009). Thus, the ability to generalize learned associations could be advantageous, particularly in a seasonal and changing environment.…”

Which traits do observers use to distinguish Batesian mimics from their models?

“…It is quite possible that a single mimic species would have reliably distinguishable colors from a single model species; but as more species are encountered, it becomes impossible to adopt a simple rule that separates one taxon from the other. Mimicry that appears "inaccurate" based on a single comparison may in fact be sufficient to provide protection from predation in a scenario where a number of model species are encountered (Ihalainen et al 2012;Easley and Hassall 2014), as in this study and likely faced by many wild predators. It is interesting to note that participants did attack larger insects less frequently during the Size treatment, despite gaining no resulting advantage.…”

“…There is an increasing appreciation that, to understand mimicry, we must take into account the complexity of the prey community (Easley and Hassall 2014) and the limited knowledge of the predator . By comparing results of simple experiments with others that confront predators with more complex prey communities and realistic situations, as done here and in other studies (Ihalainen et al 2012;Easley and Hassall 2014), we can establish the circumstances under which selection will and will not act on inaccurate mimetic signals.…”