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Ecological Theory of Population Distributions

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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  1. Ecological Theory of Population Distributions

  2. 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?

  3. But… Relationships Are Dynamic • The environment is dynamic (i.e., changing) • Site fidelity may prevent immediate response • Animal’s may acclimate producing different responses

  4. Factors Limiting Distributions • Mobility/dispersal • Habitat • Temperature, moisture, light, oxygen, vegetation, aquatic/lithic substrates • 3. Interactions with other animals

  5. Limiting Factors – Dispersal

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

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

  8. Limiting Factors - Habitat • Temperature, Moisture, Light, Oxygen • Vegetation, Aquatic or Lithic Substrates

  9. Normal Response

  10. Logistic Response

  11. Limiting Factors – Other Organisms • Intraspecific Interactions • Fretwell’s Ideal Free Distribution • The Ideal Despotic Distribution

  12. Limiting Factors – Other Organisms • Interspecific Interactions • Competition • Gause’s Competitive Exclusion • MacArthur (1958) northeastern warblers • Character displacement

  13. Interspecific CompetitionCharacter Displacement

  14. Interspecific CompetitionCharacter Displacement – Darwin’s Finches

  15. Limiting Factors – Other Organisms • Predation • Disease

  16. Limiting Factor? or Factors? • Leibig’s Law • Stressed importance of single factors limiting distributions • Does not work for interacting factors

  17. A Final Note: Hierarchy of Scales

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