Müllerian and Batesian Mimics Are Extended Phenotypes

Abstract

Aposematic signaling (by coloration, odor, texture, shape, movement, auditory) is a well-known defense across the animal and plant kingdoms, and the current hypothesis about its wide occurrence is that there is a selective advantage to this trait. Aposematic signaling evolved because predators and herbivores learn to associate it with bad taste, danger, poison, spines or unprofitable handling (Poulton 1890; Cott 1940; Edmunds 1974; Gittleman and Harvey 1980; Ruxton et al. 2004; Mappes et al. 2005; Lev-Yadun 2009a). Aposematism and mimicry of aposematic animals, especially by butterflies, were one of the first demonstrations of evolution already in Darwin’s lifetime or shortly after (Bates 1862; Müller 1879; Wallace 1889). The detailed field data collected by Bates in South America showed that chemically defended (bitter) butterflies of different taxa have similar coloration patterns (later defined as Müllerian mimicry) and that chemically non-defended ones may look like defended ones and by this gain protection (later defined as Batesian mimicry), being defense parasites. Müller (1879) gave a mathematical explanation for the phenomenon, showing that use of the same signal by several taxa may lower the cost incurred on the defended and signaling prey by unexperienced predators that attack till they learn to avoid defended and signaling types. It was later shown that increasing the number of Müllerian mimics indeed helps to reduce the cost of learning by predators, even if the various species differ in their strength of defense (Rowland et al. 2007; Sherratt 2007). It has also been shown that association of non-defended types with defended ones defends the former, a situation that may in due time result in the evolution of Batesian mimicry (de Wert et al. 2012).