Frequency-dependent selection and evolutionarily stable strategies
Evolutionarily stable strategy (ESS): a strategy that, when adopted by most of the population,
cannot be invaded by a rare mutant. ESS ≠ Nash equilibrium: ESS requires stability to invasion.
Replicator dynamics: dp/dt = p(1−p)[f(A) − f(B)], where fitness depends on current frequencies.
A pure ESS exists when a single strategy dominates; mixed ESS when both persist.