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Frequency-dependent Selection

Frequency-dependent Selection

When the fitness of a trait is influenced by how common it is (i.e., its frequency) relative to different traits within a population, this is referred to as frequency-dependent selection. Frequency-dependent selection may occur between species or within a single species. This type of selection can either be positive—with more common phenotypes having higher fitness—or negative, with rarer phenotypes conferring increased fitness.

Predator-Prey Interactions

Predator-Prey Interactions

Predators consume prey for energy. Predators that acquire prey and prey that avoid predation both increase their chances of survival and reproduction (i.e., fitness). Routine predator-prey interactions elicit mutual adaptations that improve predator offenses, such as claws, teeth, and speed, as well as prey defenses, including crypsis, aposematism, and mimicry. Thus, predator-prey interactions resemble an evolutionary arms race.

Speciation Rates

Speciation Rates

Mutation, Gene Flow, and Genetic Drift

Mutation, Gene Flow, and Genetic Drift

In a population that is not at Hardy-Weinberg equilibrium, the frequency of alleles changes over time. Therefore, any deviations from the five conditions of Hardy-Weinberg equilibrium can alter the genetic variation of a given population. Conditions that change the genetic variability of a population include mutations, natural selection, non-random mating, gene flow, and genetic drift (small population size).

Types of Selection

Types of Selection

Natural selection influences the frequencies of particular alleles and phenotypes within populations in several different ways. Primarily, natural selection can be directional, stabilizing, or disruptive. Directional selection favors one extreme trait and shifts the population towards that phenotype while selecting against individuals displaying alternate traits. Stabilizing selection favors an intermediate trait with a narrow range of variation. Deviation from the optimal phenotype towards an...

Population Growth

Population Growth

Population size is dynamic, increasing with birth rates and immigration, and decreasing with death rates and emigration. In ideal conditions with unlimited resources, populations can increase exponentially, which plots as a J-shaped growth rate curve of population size against time. This type of curve is characteristic of newly-introduced invasive species, or populations that have suffered catastrophic declines and are rebounding.

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Related Experiment Video

Updated: Mar 6, 2026

Rearing and Long-Term Maintenance of Eristalis tenax Hoverflies for Research Studies

Rearing and Long-Term Maintenance of Eristalis tenax Hoverflies for Research Studies

Published on: May 19, 2018

Vole population cycles: A case for kin-selection?

E L Charnov¹, J P Finerty¹

¹Department of Biology, University of Utah, 84112, Salt Lake City, Utah, USA.

|March 18, 2017

Summary

This summary is machine-generated.

Kin selection, a theory explaining altruistic behavior, may drive vole population cycles. Aggression between related voles supports this evolutionary hypothesis in population dynamics.

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Area of Science:

Ecology
Evolutionary Biology
Behavioral Science

Background:

Vole population cycles are a complex ecological phenomenon.
Understanding the drivers of these cycles is crucial for ecological management.
Kin selection is a theoretical framework explaining altruistic behaviors based on genetic relatedness.

Purpose of the Study:

To investigate the potential role of kin selection in regulating vole population dynamics.
To explore the relationship between social behavior, genetic relatedness, and population fluctuations in voles.

Main Methods:

Analysis of demographic data to identify population cycle patterns.
Behavioral observations focusing on aggressive interactions between voles.
Assessment of the coefficient of relation between interacting individuals.

Main Results:

Evidence of aggression between vole individuals with a low coefficient of relation was observed.
These aggressive interactions suggest potential kin-selection mechanisms at play.
Demographic and behavioral data collectively support the hypothesis.

Conclusions:

Kin selection may be a significant factor contributing to the cyclical population dynamics of voles.
The findings highlight the importance of social behavior and relatedness in population ecology.
Further research is warranted to fully elucidate the mechanisms.