ecological theory of population distributions. the concept of “niche” elton’s (1927)...
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![Page 1: Ecological Theory of Population Distributions. The Concept of “Niche” Elton’s (1927) –Emphasized animal’s place in the biotic community –What does the](https://reader030.vdocuments.us/reader030/viewer/2022032800/56649d435503460f94a1fb02/html5/thumbnails/1.jpg)
Ecological Theory of Population Distributions
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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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But… Relationships Are Dynamic
• The environment is dynamic (i.e., changing)
• Site fidelity may prevent immediate response
• Animal’s may acclimate producing different responses
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Factors Limiting Distributions
1. Mobility/dispersal
2. HabitatTemperature, 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– Fretwell’s Ideal Free Distribution
– The Ideal Despotic Distribution
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Limiting Factors – Other Organisms
• Interspecific Interactions– Competition
• Gause’s Competitive Exclusion– MacArthur (1958) northeastern warblers
• Character displacement
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Interspecific CompetitionCharacter Displacement
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Interspecific CompetitionCharacter Displacement – Darwin’s Finches
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Limiting Factors – Other Organisms
• Predation
• Disease
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Limiting Factor? or Factors?
• Leibig’s Law– Stressed importance of single factors limiting
distributions
• Does not work for interacting factors
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A Final Note: Hierarchy of Scales