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Related Concept Videos

Frequency-dependent Selection01:21

Frequency-dependent Selection

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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.
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Density is an important characteristic of substances, crucial in determining whether an object sinks or floats in a fluid. Its SI unit is kg/m3, and its cgs unit is g/cm3. The density of an object helps in identifying its composition, and also reveals information about the phase of the matter and its substructure. The densities of liquids and solids are roughly comparable, consistent with the fact that their atoms are in close contact. However, gases have much lower densities than liquids and...
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The total amount of current flowing through one unit value of a cross-sectional area is referred to as current density. If the current flow is uniform, the amount of current flowing through a conductor is the same at all points along the conductor, even if the conductor area varies. The current density consists of the local magnitude and direction of the charge flow, which varies from point to point. Current density is measured in amperes per meter square, and direction is defined as the net...
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The Collision Theory
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Medications are typically administered to achieve therapeutic effects. Some drugs can modify an individual's mood and perception, frequently resulting in various enjoyable experiences. However, this can result in drug dependency, a condition marked by continuous drug use despite potential negative consequences. Drug dependency primarily falls into two categories: psychological and physical dependence. Psychological dependence occurs when the pleasurable feelings induced by the drug...
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Contact-dependent signaling, as the name suggests, requires that communicating cells be in direct contact with each other. This is achieved either through receptor-ligand interactions or by specialized cytoplasmic channels that allow the flow of small molecules between cells. In animal cells, channels called gap junctions facilitate contact-dependent signaling in certain tissues, whereas, plasmodesmata perform a similar function in plants.
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Related Experiment Video

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Daily Transfers, Archiving Populations, and Measuring Fitness in the Long-Term Evolution Experiment with Escherichia coli
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Evolution in population parameters: density-dependent selection or density-dependent fitness?

Joseph Travis1, Jeff Leips, F Helen Rodd

  • 1Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA. jtravis@fsu.edu

The American Naturalist
|April 20, 2013
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This summary is machine-generated.

Density-dependent selection, a key concept in ecology and evolution, shows a feedback loop between population growth and natural selection. Despite its theoretical importance, empirical evidence for density-dependent selection remains elusive, posing challenges for understanding ecological-evolutionary feedbacks.

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Area of Science:

  • Ecology
  • Evolutionary Biology
  • Ecological Genetics

Background:

  • Density-dependent selection is a foundational concept linking ecological population dynamics with evolutionary processes.
  • It represents a simple feedback mechanism between organismal crowding and selective pressures.
  • This concept is crucial for understanding adaptation and coevolution in interacting species.

Purpose of the Study:

  • To trace the historical development of studying the reciprocity between ecology and evolution.
  • To critically examine the distinction between density-dependent fitness and density-dependent selection.
  • To investigate the prevalence and importance of density-dependent selection in natural systems.

Main Methods:

  • Historical review of ecological and evolutionary studies.
  • Theoretical analysis of density-dependent fitness versus density-dependent selection.
  • Examination of empirical evidence, including studies on the least killifish (Heterandria formosa).

Main Results:

  • Density-dependent fitness is frequently observed, but direct evidence for density-dependent selection is less common.
  • Theoretical distinctions exist between density-dependent fitness and selection regarding their impact on species interactions.
  • Life-history variation in Heterandria formosa suggests density-dependent selection, yet conclusive proof is difficult to obtain.

Conclusions:

  • There is a significant gap between the theoretical importance and empirical validation of density-dependent selection.
  • Challenges remain in detecting and quantifying density-dependent selection in natural populations.
  • Further research is needed to fully understand the role of density-driven feedbacks in ecological and evolutionary dynamics.