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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 Tonicella Katherina Mytilus Lithophyllum Hedophyllum 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 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 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 Keystone species Enhydra lutris Strongylocentrotus purpuratus Macrocystis pyrifera But in reality - much more complex But in reality - VERY much more complex Another take on this - Menge and Sutherland ‘87 Rat Food Web Gulls Fish Crabs Sea stars Limpet Whelk Snails Urchin Red algae Barnacles Crusts Bivalves Polychaete Emphemerals Another take on this - Menge and Sutherland ‘87 Interaction web Rat Gulls strong links Fish weak links Crabs Sea stars Limpet Whelk Snails Urchin Red algae Barnacles Crusts Bivalves Polychaete Emphemerals Community Structure Multispecies interactions - Underwood Tesseropora - barnacle Patelloida -acamaeid limpet Cellana - patellid limpet Morula - predatory whelk Community Structure Multispecies interactions - Underwood Experiment 1 - Effect of Cellana on survival of Tesseropa Morula - excluded Tesseropora Cellana -grazes open rock 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 # Cellana/enclosure 8 10 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 Experiment 2 - Effect of Tesseropa on growth of Patelloida Cellana growth rate Patelloida growth rate Tesseropa density Community Structure Multispecies interactions - Underwood General conclusion - major interactions among all components of system - no keystone species - no links are ‘weak’ Community Structure How do the forces shaping communities interact? (Menge and Sutherland, Amer. Nat. 110:351) Habitat amelioration -consider situations of a) high and low stress b) high and low recruitment Relative importance high low Stress HIGH RECRUITMENT Community Structure How do the forces shaping communities interact? (Menge and Sutherland, Amer. Nat. 110:351) Habitat amelioration Relative importance -consider situations of a) high and low stress b) high and low recruitment Competition high low Stress HIGH RECRUITMENT Community Structure How do the forces shaping communities interact? (Menge and Sutherland, Amer. Nat. 110:351) Habitat amelioration -consider situations of a) high and low stress b) high and low recruitment Predation Relative importance Competition high low Stress HIGH RECRUITMENT Community Structure How do the forces shaping communities interact? (Menge and Sutherland, Amer. Nat. 110:351) Habitat amelioration -consider situations of a) high and low stress b) high and low recruitment Predation Relative importance Competition Associational defenses high low Stress HIGH RECRUITMENT Community Structure How do the forces shaping communities interact? (Menge and Sutherland, Amer. Nat. 110:351) -consider situations of a) high and low stress b) high and low recruitment Relative importance Competition high low Stress LOW RECRUITMENT Community Structure How do the forces shaping communities interact? (Menge and Sutherland, Amer. Nat. 110:351) -consider situations of a) high and low stress b) high and low recruitment Predation Relative importance Competition high low Stress LOW RECRUITMENT Community Structure How do the forces shaping communities interact? (Menge and Sutherland, Amer. Nat. 110:351) -consider situations of a) high and low stress b) high and low recruitment Predation Relative importance Competition Associational defenses high low Stress LOW RECRUITMENT Community Structure How do the forces shaping communities interact? (Menge and Sutherland, Amer. Nat. 110:351) -consider situations of a) high and low stress b) high and low recruitment Relative importance Predation Habitat amelioration Competition Associational defenses high low Stress LOW RECRUITMENT Community Structure Relationship to diversity Diversity high low Stress Community Structure Relationship to diversity Negative effects of competition and predation Negative effects of stress Diversity high low Stress Community Structure Disturbance and Diversity Connell - Intermediate Disturbance Hypothesis Diversity Low High Disturbance (frequency, intensity, extent) Community Structure Disturbance and Diversity Connell - Intermediate Disturbance Hypothesis Competitive dominants fill space Diversity Low High Disturbance (frequency, intensity, extent) 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) 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
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