Apostatic selection is a form of negative frequency-dependent selection. 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 forms. In apostatic selection, the common forms of a species are preyed on more than the rarer forms, giving the rare forms a selective advantage in the population. It has also been discussed that apostatic selection acts to stabilize prey polymorphisms. The term "apostatic selection" was introduced in 1962 by Bryan Clarke in reference to predation on polymorphic grove snails and since then it has been used as a synonym for negative frequency-dependent selection. The behavioural basis of apostatic selection was initially neglected, but was eventually established by A.B Bond. Apostatic selection can also apply to the predator if the predator has various morphs. There are multiple concepts that are closely linked with apostatic selection. One is the idea of prey switching, which is another term used to look at a different aspect of the same phenomenon, as well as the concept of a search image. Search images are relevant to apostatic selection as it is how a predator is able to detect an organism as a possible prey. Apostatic selection is important in evolution because it can sustain a stable equilibrium of morph frequencies, and hence maintains large amounts of genetic diversity in natural populations. It is important to note however, that a rare morph being present in a population does not always mean that apostatic selection will occur, as the rare morph could be targeted at a higher rate. From a predator's view, being able to select for rare morphs actually increases the predator's own fitness. Prey switching In prey switching, predators switch from primary prey to an alternative food source for various reasons. This is related to apostatic selection because when a rare morph is being selected for, it is going to increase in abundance in a specific population until it becomes recognized by a predator. Prey switching, therefore, seems to be a result of apostatic selection. Prey switching is related to prey preference as well as the abundance of the prey. Effects on populations It has also been determined that apostatic selection causes stabilization of prey polymorphisms due to the limitations of predators' behaviour. Since the