Frequency-dependent selection

Definition

Frequency-dependent selection is a type of natural selection where the fitness of a phenotype depends on its frequency relative to other phenotypes in a given population. This concept plays a crucial role in shaping genetic diversity within populations, as it can favor rare traits or phenotypes over more common ones. The dynamic interactions between different traits create a feedback loop that can influence evolutionary trajectories and lead to balanced polymorphism.

5 Must Know Facts For Your Next Test

1. Frequency-dependent selection can lead to the maintenance of multiple phenotypes in a population, contributing to genetic diversity.
2. Negative frequency-dependent selection often occurs in predator-prey relationships, where rare prey types are less likely to be targeted by predators.
3. This type of selection can also be seen in mating systems, where individuals may prefer to mate with less common phenotypes to avoid inbreeding.
4. Positive frequency-dependent selection can lead to the fixation of certain traits within a population, potentially reducing overall genetic variation.
5. Understanding frequency-dependent selection is essential for studying evolutionary dynamics, as it illustrates how interactions between individuals shape adaptive strategies.

Review Questions

• How does negative frequency-dependent selection influence genetic diversity within a population?
  • Negative frequency-dependent selection enhances genetic diversity by favoring rare phenotypes. As these rare traits become more successful in evading predators or gaining mates, their frequencies increase, while more common traits may suffer from reduced fitness. This dynamic encourages a balance among different phenotypes, helping prevent any single trait from becoming too dominant and thereby promoting overall diversity in the gene pool.
• Discuss the role of positive frequency-dependent selection in shaping evolutionary outcomes and provide an example.
  • Positive frequency-dependent selection reinforces traits that become more common in a population. For instance, if a specific coloration provides better camouflage, individuals with that color may be favored, leading to its increased prevalence. This can ultimately reduce genetic variation as the favored trait spreads and others diminish. Over time, this can limit adaptability if environmental conditions change, highlighting the importance of understanding both positive and negative frequency-dependent selection in evolution.
• Evaluate the implications of balancing selection on population genetics and evolutionary stability.
  • Balancing selection has profound implications for population genetics as it promotes the maintenance of multiple alleles within a population. By allowing different phenotypes to coexist through mechanisms like frequency-dependent selection or heterozygote advantage, balancing selection contributes to evolutionary stability. This stability ensures that populations remain resilient to environmental changes and diseases by retaining a variety of traits that may prove advantageous under varying circumstances. Such dynamics are crucial for understanding how species adapt and evolve over time.

Related terms

Negative frequency-dependent selection: A form of frequency-dependent selection where the fitness of a phenotype increases as it becomes rarer, which helps maintain genetic diversity within populations.

Positive frequency-dependent selection: A form of frequency-dependent selection where the fitness of a phenotype increases as it becomes more common, often leading to the dominance of a particular trait.

Balancing selection: A type of natural selection that maintains multiple phenotypes in a population, often through mechanisms like frequency-dependent selection or heterozygote advantage.