What does frequency-dependent selection refer to?

Frequency-dependent selection refers to a situation where the fitness of a particular phenotype is contingent upon its frequency in the population compared to other phenotypes. This concept suggests that in a given environment, the success of a trait can vary as its prevalence changes. For example, in predator-prey interactions, if a particular color morph of prey becomes more common, predators may start to recognize and target that morph more easily, which can lead to a decrease in its frequency. Conversely, a rarer phenotype might have an advantage simply because it is less likely to be predated upon, thus influencing the selection pressure based on the frequency of each phenotype within the population.

This concept is crucial in understanding how species adapt over time and can contribute to the maintenance of genetic diversity within a population. It highlights the dynamic interplay between different phenotypes and their success in a constantly changing environment. Through frequency-dependent selection, the evolutionary fitness of organisms can shift based on their representation in the population, leading to fluctuating patterns of natural selection.