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Ecological Theory of Population Distributions

Explore Elton and Hutchinson's theories on animal niches, dynamic environmental relationships, and factors limiting populations, such as habitat and interspecific competition. Understand the complexities of species distribution dynamics and the hierarchy of scales in ecology.

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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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