Ecological theory of population distributions
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Ecological Theory of Population Distributions. The Concept of “Niche”. Elton’s (1927) Emphasized animal’s place in the biotic community What does the animal do for a living? Hutchinson’s (1957) N-dimensional hypervolume What environmental conditions does the critter occupy?.

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Ecological Theory of Population Distributions

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Ecological Theory of Population Distributions


The Concept of “Niche”

  • Elton’s (1927)

    • Emphasized animal’s place in the biotic community

    • What does the animal do for a living?

  • Hutchinson’s (1957)

    • N-dimensional hypervolume

    • What environmental conditions does the critter occupy?


But… Relationships Are Dynamic

  • The environment is dynamic (i.e., changing)

  • Site fidelity may prevent immediate response

  • Animal’s may acclimate producing different responses


Factors Limiting Distributions

  • Mobility/dispersal

  • Habitat

  • Temperature, moisture, light, oxygen, vegetation, aquatic/lithic substrates

  • 3. Interactions with other animals


Limiting Factors – Dispersal


Limiting Factors – Dispersal(e.g., Westslope and Yellowstone Cutthroat)


Limiting Factors – Dispersal(e.g., Chihuahua Darter)


Limiting Factors - Habitat

  • Temperature, Moisture, Light, Oxygen

  • Vegetation, Aquatic or Lithic Substrates


Normal Response


Logistic Response


Limiting Factors – Other Organisms

  • Intraspecific Interactions

    • Fretwell’s Ideal Free Distribution

    • The Ideal Despotic Distribution


Limiting Factors – Other Organisms

  • Interspecific Interactions

    • Competition

      • Gause’s Competitive Exclusion

        • MacArthur (1958) northeastern warblers

      • Character displacement


Interspecific CompetitionCharacter Displacement


Interspecific CompetitionCharacter Displacement – Darwin’s Finches


Limiting Factors – Other Organisms

  • Predation

  • Disease


Limiting Factor? or Factors?

  • Leibig’s Law

    • Stressed importance of single factors limiting distributions

  • Does not work for interacting factors


A Final Note: Hierarchy of Scales


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