1Ecological Theory of Population DistributionsThe 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• The environment is dynamic (i.e., changing)• Site fidelity may prevent immediate response• Animal’s may acclimate producing different responses2Factors Limiting Distributions1. Mobility/dispersal2. HabitatTemperature, moisture, light, oxygen, vegetation, aquatic/lithic substrates3. Interactions with other animals3Limiting Factors – DispersalLimiting Factors – Dispersal(e.g., Westslope and Yellowstone Cutthroat)Limiting Factors – Dispersal(e.g., Chihuahua Darter)4Limiting Factors - Habitat• Temperature, Moisture, Light, Oxygen• Vegetation, Aquatic or Lithic Substrates5Normal ResponseLogistic ResponseLimiting Factors – Other Organisms• Intraspecific Interactions– Fretwell’s Ideal Free Distribution– The Ideal Despotic Distribution6Limiting Factors – Other Organisms• Interspecific Interactions– Competition• Gause’s Competitive Exclusion– MacArthur (1958) northeastern warblers• Character displacementInterspecific CompetitionCharacter DisplacementInterspecific CompetitionCharacter Displacement – Darwin’s Finches7Limiting Factors – Other Organisms• Predation• DiseaseLimiting Factor? or Factors?• Leibig’s Law– Stressed importance of single factors limiting distributions• Does not work for interacting factorsA Final Note: Hierarchy of
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