Ecological Theory of Population Distributions

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Ecological Theory of Population Distributions
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The Concept of Niche

• Eltons (1927)
• Emphasized animals place in the biotic community
• What does the animal do for a living?
• Hutchinsons (1957)
• N-dimensional hypervolume
• What environmental conditions does the critter
  occupy?

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But Relationships Are Dynamic

• The environment is dynamic (i.e., changing)
• Site fidelity may prevent immediate response
• Animals may acclimate producing different
  responses

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Factors Limiting Distributions

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

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Limiting Factors Dispersal
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Limiting Factors Dispersal(e.g., Westslope and
Yellowstone Cutthroat)
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Limiting Factors Dispersal(e.g., Chihuahua
Darter)
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Limiting Factors - Habitat

• Temperature, Moisture, Light, Oxygen
• Vegetation, Aquatic or Lithic Substrates

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Normal Response
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Logistic Response
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Limiting Factors Other Organisms

• Intraspecific Interactions
• Fretwells Ideal Free Distribution
• The Ideal Despotic Distribution

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Limiting Factors Other Organisms

• Interspecific Interactions
• Competition
• Gauses Competitive Exclusion
• MacArthur (1958) northeastern warblers
• Character displacement

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Interspecific CompetitionCharacter Displacement
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Interspecific CompetitionCharacter Displacement
Darwins Finches
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Limiting Factors Other Organisms

• Predation
• Disease

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Limiting Factor? or Factors?

• Leibigs Law
• Stressed importance of single factors limiting
  distributions
• Does not work for interacting factors

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A Final Note Hierarchy of Scales