Evolutionary arms race

In evolutionary biology, an evolutionary arms race is a struggle between competing sets of co-evolving genes, traits, or species, that develop adaptations and counter-adaptations against each other, resembling an arms race. These are often described as examples of positive feedback. The co-evolving gene sets may be in different species, as in an evolutionary arms race between a predator species and its prey (Vermeij, 1987), or a parasite and its host. Alternatively, the arms race may be between members of the same species, as in the manipulation/sales resistance model of communication (Dawkins & Krebs, 1979) or as in runaway evolution or Red Queen effects. One example of an evolutionary arms race is in sexual conflict between the sexes, often described with the term Fisherian runaway. Thierry Lodé emphasized the role of such antagonistic interactions in evolution leading to character displacements and antagonist coevolution. The escalation hypothesis put forward by Geerat Vermeij speaks of more general conflicts and was originally based on his work with marine gastropod fossils.

Co-evolution itself is not necessarily an arms race. For example, mutualism may drive co-operative adaptations in a pair of species. This is the case with certain flowers' ultra-violet color patterns, whose function is to guide bees to the center of the flower and promote pollination. Co-evolution is also interspecific by definition; it excludes intraspecific arms races such as sexual conflict.

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