Mimicry Systems—Wolfgang Wickler’s Account
Typologies of mimicry have developed in parallel with the emergence of understanding mimicry as a formal system. Such a systemic approach to mimicry becomes widespread in research literature starting from the 1960s. The advancement of the systemic approach to mimicry could be related to the general tendency of that time to use mathematical and cybernetic approaches for analysing biological phenomena, as well as to the impact of theoretical ecology that modelled relations between species in ecological communities. Under the systemic approach to mimicry, I include authors and works that clearly distinguish and pay attention to three participants of mimicry—the mimic, the model and the receiver—and treat these as an interconnected mimicry system. The systemic approach also tends to see relations between the mimic, the model and the receiver as central factors in the evolution and dynamics of mimicry. The systemic approach thereby purifies the mimicry system and brings the unity of the mimic-model-receiver setup to the foreground in comparison to other evolutionary and ecological processes.
A central figure in developing the systemic approach to mimicry is German zoologist Wolfgang Wickler with his much-cited paper “Mimicry and the evolution of animal communication”, published in the journal Nature in 1965. Wickler was a colleague of Konrad Lorenz in the Max Planck Institute for Comparative Ethology and a true member of the classical ethology school. In his paper, Wickler addresses as a problem that earlier accounts of mimicry were mostly derived from observations of specific mimicry cases, and that commonly used theoretical concepts like protective or aggressive mimicry did not cover the full diversity of mimicry systems in nature (Wickler 1965: 519). As a solution, he proposes describing mimicry as a formal structure of three participants in which their interrelations could be expressed by mathematical symbols based on the evolutionary effect of the participants to one another (whether it is positive or negative). Wickler describes mimicry through the roles of the mimic, the model and the receiver as follows:
(1) A signal is emitted by two different signal-senders (S1, S2) which have at least one signal receiver (R) in common that reacts similarly to both of them. (2) One of the senders is called a model, the other a mimic, [...] if it is profitable (+) for the receiver to give the reaction to one of the senders, but unprofitable (-) to react in the same way towards the other. That means, that if the signals from the two senders could be distinguished by the receiver, individual experience and/or selection would favour different reactions. (Wickler 1965: 519).
Wickler calls such a communicative situation the model-mimic-receiver system or later just the mimicry system. The way in which Wickler formalises mimicry allows for quick and clear representation of different triadic relations between species. For instance, a situation where it is profitable for the receiver (R) to give a certain behavioural response to the signal (+) sent by one sender (S1), but harmful (-) to respond in the same way to a similar signal sent by a second receiver (S2) can be expressed as a formula: S1 +R- +S2. In such a situation, the first sender (S1) should be called a model and second sender (S2) a mimic. In Wickler’s schematisation, when mimicry is evolutionarily beneficial to the mimic, it is expressed by a + sign before S2. For the model S1, the evolutionary effect of mimicry relation depends on the behaviour of the receiver: it can be beneficial + (if the model has warning colouration and the typical reaction of the receiver is to avoid the model), damaging - (in the case of aggressive mimicry, where the model is the typical prey of the receiver and where the mimic imitates the prey with an aim to catch the receiver) or neutral (where the model is an object or feature of the non-living environment).
Wickler’s schematisation was meant to be quite universal and to allow for describing triadic relations between species beyond mimicry. For instance, he discusses De Ruiter’s experiment, where insectivorous birds were let into an enclosure where caterpillars with camouflage colouring were hiding in the bush branches. After finding some moth larvae, birds started to snap everything that resembled larvae (both real caterpillars and branches). Wickler formalises such a misleading situation with the formula S1- +R—S2, where S1 signifies the mimic caterpillars and S2, the models (that is, bush branches and vegetation). For birds (R), it is beneficial to catch larvae (S1) but damaging to eat branches (S2), whereas pecking is detrimental to both moth larvae and branches, expressed by the minus signs. Wickler a uses similar approach to describe Mullerian mimicry (S1+ +R+ + S2) and concludes similarly to many other authors, that as Mullerian mimicry is beneficial to all participants, it should not be taken as a case of mimicry, but rather as an example of convergence.
Wickler’s systemic approach that focuses on the three participants of mimicry and their interrelations makes it possible to describe and compare mimicry cases that take place in many different ecological relations and communicative media. Although centred on evolutionary cost-benefit relations, the tripartite approach also provides a good ground for describing biosemiotic and communicative processes and their effects on mimicry, which will be developed in the following chapters. For a semiotics of mimicry, Wickler’s observation of the receiver’s role in a mimicry system is especially relevant. According to him, it is the receiver’s long-lasting learning activity that determines the dynamics of the mimicry system (Wickler 1965: 519). In certain cases, as for instance in Mertensian mimicry, the type of the receiver’s learning process (whether its reaction is innate or acquired during ontogenesis through experience) could even be essential in determining which participant in mimicry acts as a model and which one as a receiver (Wickler 1968: 241).
In 1968, Wolfgang Wickler published a monograph “Mimicry in plants and animals”. The book included a popularising overview of mimicry types with a thoroughgoing discussion of examples in the framework of Darwinian evolutionary theory. The final part of the book presented Wickler’s own understanding of the mimicry system as a specific configuration of the mimic, the model and the receiver. The fluent scientific-popular style and a good choice of examples made Wickler’s tripartite model of the mimicry quite broadly known. His approach was later elaborated by British entomologist Richard I. Vane-Wright, who emphasised in his papers (Vane-Wright 1976, 1980, 1981) the importance of informational processes in mimicry. In regard to the receiver’s behaviour, Vane-Wright distinguished two aspects: receiving information and reacting to it, i.e. sensorial and motoric functions. There appears to be an implicit parallel to Jakob von Uexkull’s (1982) functional cycle that contains two sign-dependent connections: perception and effect that both connect an organism with the environmental object. Vane-Wright (1976: 30) further calls organisms, whose reaction depends on perceived information and who act based on learned knowledge or innate instincts, to be “sensitive receivers”. In an indirect way, the structural approach to mimicry appears to have some affinity to the thinking of old Austrian-German biological tradition.
Wickler’s approach provides the concept of mimicry with a certain autonomy and self-sufficiency. Mimicry cases can be modelled as separate phenomena on their own, distinct from the surrounding ecological and biological conditions. This turns out to be both a strength and a weakness of the tripartite approach. On the positive side, this makes formal description applicable not only to biological phenomena, but also to imitations in various human and animal communicative situations and sign systems on similar grounds. Formalising mimicry systems has promoted mathematical modelling of mimicry (Huheey 1964, 1976, 1988; Holmgren and Enquist 1999; Speed 1999) and using game theory in the study of mimicry systems (Bacharach and Gambetta 2001; Augner and Bernays 1998). In practical biological fieldwork, Wickler’s systemic approach has been applied, for instance, by Greene and McDiarmid (1981), Wong and Schiestl (2002), Grim (2005) and others.
