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 population. This concept highlights how the success of an allele can vary based on how common or rare it is, leading to dynamic changes in allele frequencies over time. It plays a crucial role in maintaining genetic diversity within populations, influencing evolutionary trajectories.

5 Must Know Facts For Your Next Test

1. Frequency-dependent selection can create cyclical patterns in population dynamics, as shifts in phenotype frequencies can lead to changes in selective pressures.
2. In predator-prey systems, prey that are less common can have survival advantages because predators may become specialized in hunting the more frequent types.
3. This type of selection can contribute to the maintenance of polymorphism, where multiple phenotypes coexist within a population, enhancing its adaptability.
4. Frequency-dependent selection is significant in sexual selection, as mate choice can be influenced by the prevalence of specific traits within a population.
5. The concept underscores the interconnectedness of evolutionary strategies, showing how the success of one phenotype affects others in the same environment.

Review Questions

• How does frequency-dependent selection influence the dynamics of predator-prey interactions?
  • Frequency-dependent selection plays a vital role in predator-prey dynamics by affecting the survival and reproduction rates of different prey phenotypes. For instance, when certain prey types become common, predators may focus their hunting efforts on them, giving rare types an advantage. As these rare types increase in frequency, the selective pressure shifts back towards the now common types. This constant cycle promotes diversity among prey populations and helps maintain ecological balance.
• Discuss the implications of negative and positive frequency-dependent selection on genetic diversity within populations.
  • Negative frequency-dependent selection promotes genetic diversity by favoring rare phenotypes, ensuring that no single trait becomes overwhelmingly dominant. In contrast, positive frequency-dependent selection can reduce diversity as common phenotypes gain fitness advantages and may lead to fixation of those traits. Both forms of selection illustrate how varying selective pressures can influence allele frequencies and contribute to the evolutionary trajectory of populations.
• Evaluate how frequency-dependent selection contributes to the concept of balancing selection and its importance in evolutionary biology.
  • Frequency-dependent selection is closely related to balancing selection as both mechanisms help maintain genetic diversity within populations. By favoring different phenotypes depending on their frequency, frequency-dependent selection ensures that multiple alleles persist over time, even under changing environmental conditions. This is crucial for the resilience and adaptability of species facing fluctuating ecosystems. The interplay between these selections highlights how complex evolutionary processes shape biodiversity and promote stability within populations.

Related terms

Negative frequency-dependent selection: A form of frequency-dependent selection where rare phenotypes have a higher fitness than common ones, promoting diversity within a population.

Positive frequency-dependent selection: A type of frequency-dependent selection where common phenotypes have a fitness advantage over rare ones, potentially leading to the dominance of certain traits.

Balancing selection: A form of natural selection that maintains multiple alleles in a population by favoring heterozygotes or different phenotypes under varying environmental conditions.