SIMULATION OF COEVOLUTION IN BATESIAN MIMICRY

Abstract

Coevolution may be defined as an evolutionary change in a trait of one species in response to a change in a trait of a second species, followed by an evolutionary response by the second species to the changes in the first. Yet, more complex evolutionary relationships are known to occur, such as Batesian mimicry, where three or more separate species interact along their evolutionary history. Do these complex interactions involve coevolution? In order to explore possible answers to this question, we built an agent based simulation model in which we monitored the evolution of the characteristics of individuals in a Batesian mimicry system consisting of predators, noxious prey or toxic models, non-noxious prey mimicking the toxic model, and non-mimic non-noxious prey or alternate prey. The evolutionary game consisted in Predators evolving genetic mechanisms for avoiding preying on Toxic Models, in Toxic Models evolving anti-predator toxins and signals for Predators, and in Mimics evolving mimic anti-predator signals, taking as a modeling reference the case of the evolution of harmless look-alikes of venomous coral snakes is taken as a reference. Results showed that a likely evolutionary scenario for Batesian mimicry is a mutual selective pressure between Predators and Toxic Models (i.e. Predators and Models coevolve), a selective pressure acting from Predators on Mimics, and a “dilution effect” exerted by Mimics and Alternative Prey upon the Predator-Model interaction. Alternative genetic mechanisms by Predators to avoid toxins in Models (resistance), slows Predator-Model coevolution. The simulations provide for the following testable predictions: Mimics will not coevolve with Predators nor Models but evolves in response of selective pressure from Predators without affecting the evolution of Predators nor Models. Predators and Models have to affect each others population significantly in order for a Batesian ring to get established. Deterrents in Models have to be very toxic against Predators in order to allow the establishment of a Batesian mimicry ring. Key words: Batesian, mimicry, population dynamics, toxins