Mimicry in motion and morphology: do information limitation, trade-offs or compensation relax selection for mimetic accuracy?

Donald James Mclean,Marie E Herberstein

doi:10.1098/rspb.2021.0815

Donald James Mclean, Marie E Herberstein

Open Access

https://doi.org/10.1098/rspb.2021.0815

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Abstract

Many animals mimic dangerous or undesirable prey as a defence from predators. We would expect predators to reliably avoid animals that closely resemble dangerous prey, yet imperfect mimics are common across a wide taxonomic range. There have been many hypotheses suggested to explain imperfect mimicry, but comparative tests across multiple mimicry systems are needed to determine which are applicable, and which—if any—represent general principles governing imperfect mimicry. We tested four hypotheses on Australian ant mimics and found support for only one of them: the information limitation hypothesis. A predator with incomplete information will be unable to discriminate some poor mimics from their models. We further present a simple model to show that predators are likely to operate with incomplete information because they forage and make decisions while they are learning, so might never learn to properly discriminate poor mimics from their models. We found no evidence that one accurate mimetic trait can compensate for, or constrain, another, or that rapid movement reduces selection pressure for good mimicry. We argue that information limitation may be a general principle behind imperfect mimicry of complex traits, while interactions between components of mimicry are unlikely to provide a general explanation for imperfect mimicry.

Highlights

Mimicry is the phenotypic resemblance of a mimic to a model
When trained on ants and non-mimics only, identification of mimics as prey reduced to 56%, incorrect identification of ants decreased to 3% and non-mimic identifications were unchanged at 94%
The hypothesis was explained in terms of salient traits ‘overshadowing’ other, less salient traits [7], whereas we have shown that the interpretation of a single complex trait may depend on the amount of information available to the predator

Summary

Introduction

Mimicry is the phenotypic resemblance of a mimic to a model. Mimicry comprises one or more signals that have been selected—by signal receivers—for their similarity to corresponding signals or cues in their models [1]. In this context, the signal conveys information that elicits a behavioural response in the receiver [2]. Traditional mimicry theory assumed that perfect mimicry was the optimal phenotype. When signal receivers suffer the loss of fitness from failing to discriminate mimics from models (e.g. in deceptive mimicry), the optimal signal receiver behaviour is perfect discrimination [5]. The existence of imperfect mimics can be considered an evolutionary puzzle, since either the mimetic resemblance and/or receiver behaviour is apparently not optimal [6]

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