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

Ecological Theory of Population Distributions


The concept of niche

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

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

Factors Limiting Distributions

  • Mobility/dispersal

  • Habitat

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

  • 3. Interactions with other animals


Ecological theory of population distributions

Limiting Factors – Dispersal


Limiting factors dispersal e g westslope and yellowstone cutthroat

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


Limiting factors dispersal e g chihuahua darter

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


Limiting factors habitat

Limiting Factors - Habitat

  • Temperature, Moisture, Light, Oxygen

  • Vegetation, Aquatic or Lithic Substrates


Normal response

Normal Response


Logistic response

Logistic Response


Limiting factors other organisms

Limiting Factors – Other Organisms

  • Intraspecific Interactions

    • Fretwell’s Ideal Free Distribution

    • The Ideal Despotic Distribution


Limiting factors other organisms1

Limiting Factors – Other Organisms

  • Interspecific Interactions

    • Competition

      • Gause’s Competitive Exclusion

        • MacArthur (1958) northeastern warblers

      • Character displacement


Interspecific competition character displacement

Interspecific CompetitionCharacter Displacement


Ecological theory of population distributions

Interspecific CompetitionCharacter Displacement – Darwin’s Finches


Limiting factors other organisms2

Limiting Factors – Other Organisms

  • Predation

  • Disease


Limiting factor or factor s

Limiting Factor? or Factors?

  • Leibig’s Law

    • Stressed importance of single factors limiting distributions

  • Does not work for interacting factors


Ecological theory of population distributions

A Final Note: Hierarchy of Scales


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