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 linkweak 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 linkweak 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 linkweak links Module 1Module 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 CrabsSea stars Whelk Urchin LimpetSnails Crusts Emphemerals Red algae Polychaete Barnacles Bivalves Food Web

Another take on this - Menge and Sutherland ‘87 Rat Gulls Fish CrabsSea stars Whelk Urchin LimpetSnails Crusts Emphemerals 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 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 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 Stress high low HIGH RECRUITMENT Habitat amelioration

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 Stress high low HIGH RECRUITMENT Habitat amelioration Competition

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 Stress high low HIGH RECRUITMENT Habitat amelioration Competition Predation

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 Stress high low HIGH RECRUITMENT Habitat amelioration Competition Predation Associational defenses

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 Stress high low LOW RECRUITMENT Competition

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 Stress high low LOW RECRUITMENT Competition Predation

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 Stress high low LOW RECRUITMENT Competition Predation Associational defenses

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 Stress high low LOW RECRUITMENT Habitat amelioration Competition Predation Associational defenses

Community Structure Relationship to diversity Stress high low Diversity

Community Structure Relationship to diversity Stress high low Diversity Negative effects of stress Negative effects of competition and predation

Community Structure Disturbance and Diversity Connell - Intermediate Disturbance Hypothesis Disturbance (frequency, intensity, extent) Diversity LowHigh

Community Structure Disturbance (frequency, intensity, extent) Diversity Disturbance and Diversity Connell - Intermediate Disturbance Hypothesis Competitive dominants fill space LowHigh

Community Structure Disturbance (frequency, intensity, extent) Diversity Disturbance and Diversity Connell - Intermediate Disturbance Hypothesis Competitive dominants fill space Few species can invade or persist LowHigh

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 Inhibitionlowhigh Tolerancemidrangelow Facilitationhigh high or low