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COMMUNITY STRUCTURE
Community Structure
Paine ‘80 - Keystone Species
Keystone species-a relatively low biomass species that is a
major factor in determining community structure
Community Structure
Paine ‘80 - Keystone Species
Introduced concept of ‘links’ in community
e.g. Pisaster and Mytilus
Pisaster
Mytilus
Tonicella
Lithophyllum
Katherina
Hedophyllum
Community Structure
Paine ‘80 - Keystone Species
Introduced concept of ‘links’ in community
e.g. Pisaster and Mytilus
Pisaster
Mytilus
Tonicella
Lithophyllum
Katherina
Hedophyllum
strong link weak links
Community Structure
Paine ‘80 - Keystone Species
Introduced concept of ‘links’ in community
e.g. Pisaster and Mytilus
Pisaster
Mytilus
Tonicella
Lithophyllum
Katherina
Hedophyllum
strong link weak links
Module 1
Community Structure
Paine ‘80 - Keystone Species
Introduced concept of ‘links’ in community
e.g. Pisaster and Mytilus
Pisaster
Mytilus
Tonicella
Lithophyllum
Katherina
Hedophyllum
strong link weak links
Module 1 Module 2
Keystone species
Strongylocentrotus purpuratus
Enhydra lutris
Macrocystis pyrifera
But in reality - much more complex
But in reality - VERY much more complex
Another take on this - Menge and Sutherland ‘87
Rat Gulls
Fish
Crabs Sea stars
Whelk
Urchin
Limpet Snails
CrustsEmphemerals
Red algae
Polychaete
Barnacles
Bivalves
Food Web
Another take on this - Menge and Sutherland ‘87
Rat Gulls
Fish
Crabs Sea stars
Whelk
Urchin
Limpet Snails
CrustsEmphemerals
Red algae
Polychaete
Barnacles
Bivalves
Interaction web
strong links
weak links
Community Structure
Multispecies interactions - Underwood
Tesseropora - barnacle
Cellana - patellid limpet
Patelloida -acamaeid limpet
Morula - predatory whelk
Community Structure
Multispecies interactions - Underwood
Tesseropora
Experiment 1 - Effect of Cellana on survival of Tesseropa
Cellana-grazes open rock
Morula - excluded
Community Structure
Multispecies interactions - Underwood
Experiment 1 - Effect of Cellana on survival of Tesseropa
% Tesseropora surviving
# Cellana/enclosure
0 2 4 6 8 10
Higher survivorship at intermediate density
Community Structure
Multispecies interactions - Underwood
Experiment 2 - Effect of Tesseropa on growth of Cellana
Cellana growth rate
Tesseropa density
Community Structure
Multispecies interactions - Underwood
Experiment 2 - Effect of Tesseropa on growth of Cellana
Cellana growth rate
Tesseropa density
Experiment 2 - Effect of Tesseropa on growth of Patelloida
Patelloida growth rate
Community Structure
Multispecies interactions - Underwood
General conclusion
- major interactions among all components of system
- no keystone species - no links are ‘weak’
Community StructureHow do the forces shaping communities interact?(Menge and Sutherland, Amer. Nat. 110:351)
-consider situations of a) high and low stressb) high and low recruitment
Relative importance
Stress
high low
HIGH RECRUITMENT
Habitat amelioration
Community StructureHow do the forces shaping communities interact?(Menge and Sutherland, Amer. Nat. 110:351)
-consider situations of a) high and low stressb) high and low recruitment
Relative importance
Stress
high low
HIGH RECRUITMENT
Habitat amelioration
Competition
Community StructureHow do the forces shaping communities interact?(Menge and Sutherland, Amer. Nat. 110:351)
-consider situations of a) high and low stressb) high and low recruitment
Relative importance
Stress
high low
HIGH RECRUITMENT
Habitat amelioration
Competition
Predation
Community StructureHow do the forces shaping communities interact?(Menge and Sutherland, Amer. Nat. 110:351)
-consider situations of a) high and low stressb) high and low recruitment
Relative importance
Stress
high low
HIGH RECRUITMENT
Habitat amelioration
Competition
Predation
Associational defenses
Community StructureHow do the forces shaping communities interact?(Menge and Sutherland, Amer. Nat. 110:351)
-consider situations of a) high and low stressb) high and low recruitment
Relative importance
Stress
high low
LOW RECRUITMENT
Competition
Community StructureHow do the forces shaping communities interact?(Menge and Sutherland, Amer. Nat. 110:351)
-consider situations of a) high and low stressb) high and low recruitment
Relative importance
Stress
high low
LOW RECRUITMENT
Competition
Predation
Community StructureHow do the forces shaping communities interact?(Menge and Sutherland, Amer. Nat. 110:351)
-consider situations of a) high and low stressb) high and low recruitment
Relative importance
Stress
high low
LOW RECRUITMENT
Competition
Predation
Associational defenses
Community StructureHow do the forces shaping communities interact?(Menge and Sutherland, Amer. Nat. 110:351)
-consider situations of a) high and low stressb) high and low recruitment
Relative importance
Stress
high low
LOW RECRUITMENT
Habitat amelioration
Competition
Predation
Associational defenses
Community StructureRelationship to diversity
Stress
high low
Diversity
Community StructureRelationship to diversity
Stress
high low
Diversity
Negative effects of stress
Negative effects of competition and
predation
Community StructureDisturbance and Diversity
Connell - Intermediate Disturbance Hypothesis
Disturbance(frequency, intensity, extent)
Diversity
Low High
Community Structure
Disturbance(frequency, intensity, extent)
Diversity
Disturbance and Diversity
Connell - Intermediate Disturbance Hypothesis
Competitive dominants fill
space
Low High
Community Structure
Disturbance(frequency, intensity, extent)
Diversity
Disturbance and Diversity
Connell - Intermediate Disturbance Hypothesis
Competitive dominants fill
space
Few species can invade or persist
Low High
Models of succession
1. 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/Semibalanus)
3. Facilitation- initial colonizers facilitate success of later colonizers (e.g. protection of
barnacles growth of algae
Models of succession -probably work in different areas
Habitat stress
Recruitment
Inhibition low high
Tolerance midrange low
Facilitation high high or low
