Apostatic selection is a synonym for negative frequency-dependent selection. In lay terms it describes the survival of individual prey animals that are different (through mutation) from their species in a way that makes it more likely for them to be ignored by their predators. It operates on polymorphic species, species which have different morphological forms. In negative frequency-dependent selection, the common forms of a species are preyed on more than the rarer forms and this allows the rare morphs to have a selective advantage in the population.