Frequency-dependent selection is the term given to an evolutionary process where the fitness of a phenotype is dependent on its frequency relative to other phenotypes in a given population.
- In positive (or purifying) frequency-dependent selection, the fitness of a phenotype increases as it becomes more common.
- In negative (or diversifying) frequency-dependent selection, the fitness of a phenotype increases as it becomes rarer. This is an example of balancing selection.
Frequency-dependent selection is usually the result of interactions between species (predation, parasitism, or competition) or between genotypes within species (usually competitive or symbiotic), and has been especially frequently discussed with relation to anti-predator adaptations. Frequency-dependent selection can lead to polymorphic equilibria which result from interactions among genotypes within species, in the same way that multi-species equilibria require interactions between species in competition (e.g. where αij parameters in Lotka-Volterra competition equations are non-zero).
Read more about Frequency-dependent Selection: Negative Frequency-dependent Selection, Positive Frequency-dependent Selection
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