COMMUNITY ECOLOGY

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CHAPTER 53

• COMMUNITY ECOLOGY

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A Savanna Community
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COMMUNITY ECOLOGY

• The Community
• Species Richness
• Relative Abundance
• Community Structure
• Individualistic Hypothesis
• Interactive Hypothesis
• Rivet Model
• Redundancy Model

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INTERSPECIFIC COMPETITION

• Interspecific Competition - Two or More
  Species - Similar Limiting Resources
• Interference Competition
• Exploitative Competition
• Competitive Exclusion Principle
• Ecological Niche Total of the use of Biotic
  and Abiotic Resources in the Environment.
• Fundamental Niche - Resources a Species Can Use
  Under Ideal Conditions
• Realized Niche - Resources Actually Used

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Competitive Exclusion
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Resource Partitioning
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Character Displacement
The tendency of a character to be more
divergent in sympatric populations than
allopatric populations.
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COMMUNITY INTERACTIONS

• Coevolution
• Predator-Prey Interactions
• May Involve Many Species
• Passiflora and Heliconius

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INTERSPECIFIC INTERACTIONS

• Interspecific Interactions
• Positive ()
• Negative (-)
• Neutral (0)
• Predator and Parasitism (-) Interactions
• Predation Predator/Prey
• Parasitism
• Parasitoidism
• Herbivory

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Parasitic behavior A female Nasonia vitripennis
laying a clutch of eggs into the pupa of a
blowfly (Phormia regina)
Parasitism
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INTERSPECIFIC INTERACTIONS

• Predation
• Predator Prey Interactions
• Predator Adaptations
• Prey Adaptations
• Plants and Herbivory
• Thorns
• Secondary Chemicals

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INTERSPECIFIC INTERACTIONS

• Animal Defenses
• Cryptic Coloration
• Deceptive Coloration
• Mechanical and Chemical Defense
• Toxins From Plants
• Aposematic Coloration Shared Warning
  Coloration.

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Camouflage Poor-will (left), lizard (right)
Cryptic Coloration
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Deceptive coloration moth with "eyeballs"
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Aposematic (warning) Coloration
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INTERSPECIFIC INTERACTIONS

• Mimicry
• Batesian Mimicry
• Mimic a Harmful Model
• Mullerian Mimicry
• Two or More Unpalatable Species Resemble.
• Predators
• Turtle and Tongue

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Batesian Mimicry
Green Tree Snake
Hawk Moth Larva
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Müllerian Mimicry
Cuckoo Bee
Yellow Jacket
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INTERSPECIFIC INTERACTIONS

• Parasitism (-)
• Parasite - Host
• Endoparasites
• Ectoparasites
• Infection/Disease
• Host Defense
• Plant - Toxins to prevent infection
• Immune Systems
• Coevolution between Host and Parasite

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SYMBIOSIS
Parasitism (-) Commensalism (0) Mutualism ()
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Interspecific Interactions and Symbiosis
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Mutualism and Commensalism
Acacia and Ants
Cattle Egret and Water Buffalo
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Species Diversity

• Species Richness Total number of different
  species.
• Relative Abundance Proportion of the total
  represented by each species in the community.
• Keystone Species Dominant species in
  community, exerts strong controls on community
  structure.

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Community Structure

• Feeding Relationships
• Trophic Levels
• Food Chains
• Food Webs

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Figure 53.10 Examples of terrestrial and marine
food chains
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Figure 53.11 An antarctic marine food web
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Limits on Food Chain Length

• Energetic Hypothesis Based on an average of
  10 efficiency in biomass to biomass conversion
  from trophic level to trophic level.
• Dynamic Stability Hypothesis Based on long
  food chains being less stable. Population
  fluctuations at lower levels could negatively
  impact higher trophic levels.

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Control on Community Structure

• Dominant Species Most abundant, high biomass.
• Invasive Species May have high biomass due
  to a lack of controls.
• Keystone Species May not be most abundant,
  but exerts a strong influence on community
  structure.
• Ecosystem Engineers (Foundation Species)

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Keystone Species
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Ecosystem Engineers
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Bottom-Up and Top-Down Controls
Bottom-up-model N V H
P This model suggest a unidirectional
influence. Top-down-model N V H
P Also called the Trophic Cascade
Model, if A lake community has four trophic
levels andthe top predator is removed the
primary carnivorewill increase, causing a
decrease in the herbivore level, an increase in
phytoplankton, thus reducingthe nutrient level.
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Disturbance and Community Composition

• Disturbance implies negative impact,
• but that may not always be the case.
• Fire controlled communities
• Intermediate Disturbance Hypothesis
• Low Disturbance May result in fewer species.
• High Disturbance Fewer species.

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Fire Control
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Succession

• Ecological Succession
• Primary Succession
• Secondary Succession
• Climax Community
• Seres
• Some communities may fluctuate rather than
  being stable.
• Causes of Succession
• r-selection
• K-selection

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SUCCESSION

• Primary Succession
• Xerosere - Bare Rock
• Pioneer Community
• Faciliate, Inhibit, Tolerate
• Seres - Successional Stages
• Climax Community
• Climax Vegetation
• Hydrosere - Pond to Terrestrial
• Pond
• Filling Stages
• Terrestrial Stages

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Primary Succession
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Glacial Retreat in Southeastern Alaska
Example of Primary Succession
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Stages of Succession
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Secondary Succession
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BIOGEOGRAPHY

• Study of past and present distribution of
• communities and individuals.
• Equatorial-Polar Gradients
• Evapotranspiration
• Rate of Speciation 5X in Tropics
• Starting Over
• Area Effects Species-Area Curves
• Island Equilibrium Model
• Degree of Isolation and Size of Island
• Immigration vs. Extinction

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Influences on Species Diversity
Evapotranspiration
Area Effects
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Island Equilibrium
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Island Size and Species Richness