Darwin's Principle of Divergence explains sympatric speciation as gradual and directional. Contradicting evidence suggests that species' traits evolve saltationally. Here, we model coevolution in exploiter-victim systems. Victims (resource population) have heritable, mutable cue phenotypes with different levels of defense. Exploiters have heritable, mutable perceptual phenotypes. Our simulations reveal coevolution of victim mimicry and exploiter specialization in a saltational and reversible cycle. Evolution is gradual and directional only in the specialization phase of the cycle thereby implying that specialization itself is saltational in such systems. Once linked to assortative mating, exploiter specialization provides conditions for speciation.
Norrström N, Getz WM, Holmgren NM. (2007). Coevolution of exploiter specialization and victim mimicry can be cyclic and saltational. Evolutionary bioinformatics online, (2)