counteradaptation

Counteradaptation is a term used in evolutionary biology to describe an adaptive change in one species that arises in response to the adaptations of another. It is a form of reciprocal evolution that can drive ongoing genetic and behavioral changes in interacting populations.

In coevolution, counteradaptation can fuel an arms race, a cycle of adaptations and counter-adaptations that continues as long as the interacting parties coexist. The Red Queen hypothesis is often invoked to explain why this ongoing process can occur even without net gains in relative fitness.

Examples include predator-prey dynamics, where prey evolve defenses such as camouflage or toxins and predators respond with improved detection, speed, or resistance. Host-parasite interactions show hosts strengthening immune defenses while parasites evolve methods to evade them. Bacteria facing antibiotics may acquire resistance, while new drugs and stewardship strategies counteract these changes.

Counteradaptation is not limited to biology. In agriculture, pests may adapt to crop resistance genes, prompting breeders to deploy new varieties; in cybersecurity, attackers develop countermeasures to defenses and defenders respond with updated protocols. In social systems, individuals or organizations adapt tactics in response to others' strategies, sometimes creating cyclical shifts in behavior.

Understanding counteradaptation helps explain patterns of biodiversity, disease dynamics, and the challenges of managing evolving threats in medicine and agriculture. See also coevolution, Red Queen hypothesis, and evolutionary arms race.