COMMUNITY%20STRUCTURE

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COMMUNITY STRUCTURE
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Community Structure
Paine 80 - Keystone Species
Keystone species -a relatively low biomass
species that is a major factor in determining
community structure
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Community Structure
Paine 80 - Keystone Species
Introduced concept of links in community
e.g. Pisaster and Mytilus
Pisaster
Tonicella
Katherina
Mytilus
Lithophyllum
Hedophyllum
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Community Structure
Paine 80 - Keystone Species
Introduced concept of links in community
e.g. Pisaster and Mytilus
strong link
weak links
Pisaster
Tonicella
Katherina
Mytilus
Lithophyllum
Hedophyllum
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Community Structure
Paine 80 - Keystone Species
Introduced concept of links in community
e.g. Pisaster and Mytilus
strong link
weak links
Pisaster
Tonicella
Katherina
Mytilus
Lithophyllum
Hedophyllum
Module 1
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Community Structure
Paine 80 - Keystone Species
Introduced concept of links in community
e.g. Pisaster and Mytilus
strong link
weak links
Pisaster
Tonicella
Katherina
Mytilus
Lithophyllum
Hedophyllum
Module 1
Module 2
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Keystone species
Enhydra lutris
Strongylocentrotus purpuratus
Macrocystis pyrifera
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But in reality - much more complex
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But in reality - VERY much more complex
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Another take on this - Menge and Sutherland 87
Food Web
Rat
Gulls
Fish
Crabs
Sea stars
Limpet
Snails
Whelk
Urchin
Red algae
Barnacles
Crusts
Emphemerals
Polychaete
Bivalves
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Another take on this - Menge and Sutherland 87
Interaction web
Rat
Gulls
strong links
Fish
weak links
Crabs
Sea stars
Limpet
Snails
Whelk
Urchin
Red algae
Barnacles
Crusts
Emphemerals
Polychaete
Bivalves
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Community Structure
Multispecies interactions - Underwood
Patelloida -acamaeid limpet
Tesseropora - barnacle
Morula - predatory whelk
Cellana - patellid limpet
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Community Structure
Multispecies interactions - Underwood
Experiment 1 - Effect of Cellana on survival of
Tesseropa
Morula - excluded
Tesseropora
Cellana -grazes open rock
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Community Structure
Multispecies interactions - Underwood
Experiment 1 - Effect of Cellana on survival of
Tesseropa
Higher survivorship at intermediate density
Tesseropora surviving
0 2 4 6 8 10
Cellana/enclosure
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Community Structure
Multispecies interactions - Underwood
Experiment 2 - Effect of Tesseropa on growth of
Cellana
Cellana growth rate
Tesseropa density
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Community Structure
Multispecies interactions - Underwood
Experiment 2 - Effect of Tesseropa on growth of
Cellana
Experiment 2 - Effect of Tesseropa on growth of
Patelloida
Cellana growth rate
Patelloida growth rate
Tesseropa density
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Community Structure
Multispecies interactions - Underwood
General conclusion - major interactions among
all components of system - no keystone species
- no links are weak
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Community Structure
How do the forces shaping communities
interact? (Menge and Sutherland, Amer. Nat.
110351)
-consider situations of a) high and low
stress b) high and low recruitment
Habitat amelioration
Relative importance
high
low
Stress
HIGH RECRUITMENT
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Community Structure
How do the forces shaping communities
interact? (Menge and Sutherland, Amer. Nat.
110351)
-consider situations of a) high and low
stress b) high and low recruitment
Habitat amelioration
Relative importance
Competition
high
low
Stress
HIGH RECRUITMENT
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Community Structure
How do the forces shaping communities
interact? (Menge and Sutherland, Amer. Nat.
110351)
-consider situations of a) high and low
stress b) high and low recruitment
Habitat amelioration
Predation
Relative importance
Competition
high
low
Stress
HIGH RECRUITMENT
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Community Structure
How do the forces shaping communities
interact? (Menge and Sutherland, Amer. Nat.
110351)
-consider situations of a) high and low
stress b) high and low recruitment
Habitat amelioration
Predation
Relative importance
Competition
Associational defenses
high
low
Stress
HIGH RECRUITMENT
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Community Structure
How do the forces shaping communities
interact? (Menge and Sutherland, Amer. Nat.
110351)
-consider situations of a) high and low
stress b) high and low recruitment
Relative importance
Competition
high
low
Stress
LOW RECRUITMENT
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Community Structure
How do the forces shaping communities
interact? (Menge and Sutherland, Amer. Nat.
110351)
-consider situations of a) high and low
stress b) high and low recruitment
Predation
Relative importance
Competition
high
low
Stress
LOW RECRUITMENT
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Community Structure
How do the forces shaping communities
interact? (Menge and Sutherland, Amer. Nat.
110351)
-consider situations of a) high and low
stress b) high and low recruitment
Predation
Relative importance
Competition
Associational defenses
high
low
Stress
LOW RECRUITMENT
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Community Structure
How do the forces shaping communities
interact? (Menge and Sutherland, Amer. Nat.
110351)
-consider situations of a) high and low
stress b) high and low recruitment
Predation
Habitat amelioration
Relative importance
Competition
Associational defenses
high
low
Stress
LOW RECRUITMENT
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Community Structure
Relationship to diversity
Diversity
high
low
Stress
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Community Structure
Relationship to diversity
Negative effects of competition and predation
Negative effects of stress
Diversity
high
low
Stress
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Community Structure
Disturbance and Diversity Connell - Intermediate
Disturbance Hypothesis
Diversity
Low High
Disturbance (frequency, intensity, extent)
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Community Structure
Disturbance and Diversity Connell - Intermediate
Disturbance Hypothesis
Competitive dominants fill space
Diversity
Low High
Disturbance (frequency, intensity, extent)
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Community Structure
Disturbance and Diversity Connell - Intermediate
Disturbance Hypothesis
Competitive dominants fill space
Few species can invade or persist
Diversity
Low High
Disturbance (frequency, intensity, extent)
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Models of succession

• Inhibition
• initial colonizers inhibit future colonizers.

• 2. Tolerance
• initial colonizers do not affect later
  colonizers. Organisms best suited to local
  conditions will persist (e.g. Chthalamus/Semibalan
  us)

• 3. Facilitation
• initial colonizers facilitate success of later
  colonizers (e.g. protection of barnacles
  growth of algae

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Models of succession -probably work in
different areas
Habitat stress Recruitment
Inhibition low high
Tolerance midrange low
Facilitation high high or low