title: The evolutionarily stable strategy under individual condition and tactic frequency.
abstract: A proof is presented to show that, when fitnesses from alternative tactics within a population depend on both their frequency and the phenotypic condition of individuals, there will be a unique ESS switchpoint s* that determines both the condition at which an individual will switch between tactics and the resulting frequency of the tactics in the population. For an individual at the ESS s*, the fitnesses of the alternative tactics will be equal. When fitness is averaged over the population, however, the average fitnesses of the alternative tactics will not be equal.
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D005075:Biological Evolution; D008433:Mathematics; D008954:Models, Biological; D010641:Phenotype