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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.Positive Frequency-Dependent SelectionIn positive...

Competition

Competition

When organisms require the same limited resources within an environment, they may have to compete for them. Competition is a net-negative interaction. Even if two competing individuals or populations do not interact directly, the overall fitness of both competitors is lowered as a result of not having full access to the limited resource.Intraspecific competition, which occurs between individuals of the same species, serves as a natural mechanism for regulating population size. Too much...

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...

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.Although predation is commonly associated with carnivory, for...

Microbial Interactions: Competition

Microbial Interactions: Competition

Microbial competition is an ecological interaction in which microorganisms vie for limited resources within shared environments. These resources may include nutrients, space, or light, depending on the system. The intensity and outcome of competition are influenced by the environmental context, such as nutrient availability, spatial constraints, and the diversity of microbial species present. These competitive interactions significantly influence the structure, function, and resilience of...

Speciation Rates

Speciation Rates

Speciation can proceed at markedly different rates, and evolutionary biologists commonly describe these differences through the models of gradualism and punctuated equilibrium. Both patterns explain how new species arise, but they differ in the tempo and continuity of evolutionary change. In both cases, evolutionary change arises from heritable variation within populations, with natural selection often shaping traits that improve survival and reproduction under specific environmental conditions.

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Competition between Species: Frequency Dependence.

Science (New York, N.Y.)

|February 26, 1971

Summary

This summary is machine-generated.

Two Drosophila species competing for resources can coexist stably. Their survival rates depend on their population sizes, demonstrating frequency-dependent fitness and stable coexistence.

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Area of Science:

Ecology
Evolutionary Biology
Population Genetics

Background:

Species coexistence despite resource competition is a long-standing ecological question.
Understanding the factors that allow competing species to coexist is crucial for biodiversity maintenance.

Purpose of the Study:

To investigate the conditions under which two competing species can achieve stable coexistence.
To determine the role of frequency-dependent fitness in interspecific competition.

Main Methods:

Laboratory populations of two Drosophila species were established.
The relative fitness of each species was measured at different initial frequencies.
Competition experiments were conducted with limited resources.

Main Results:

The relative fitness of each Drosophila species was inversely proportional to its relative frequency in the population.
This inverse relationship indicates frequency-dependent selection.
Stable coexistence was observed between the two competing species.

Conclusions:

Frequency-dependent fitness is a key mechanism promoting the stable coexistence of competing species.
Interspecific competition does not necessarily lead to competitive exclusion.
The findings resolve decades of controversy regarding stable species coexistence under competition.