COMMUNITY STRUCTURE

1. COMMUNITY STRUCTURE

2. Community Structure Paine ‘80 - Keystone Species Keystone species -a relatively low biomass species that is a major factor in determining community structure

3. Community Structure Paine ‘80 - Keystone Species Introduced concept of ‘links’ in community e.g. Pisaster and Mytilus Pisaster Tonicella Katherina Mytilus Lithophyllum Hedophyllum

4. 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

5. 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

6. 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

7. Keystone species Enhydra lutris Strongylocentrotus purpuratus Macrocystis pyrifera

8. But in reality - much more complex

9. But in reality - VERY much more complex

10. 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

11. 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

12. Community Structure Multispecies interactions - Underwood Patelloida -acamaeid limpet Tesseropora - barnacle Morula - predatory whelk Cellana - patellid limpet

13. Community Structure Multispecies interactions - Underwood Experiment 1 - Effect of Cellana on survival of Tesseropa Morula - excluded Tesseropora Cellana -grazes open rock

14. 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

15. Community Structure Multispecies interactions - Underwood Experiment 2 - Effect of Tesseropa on growth of Cellana Cellana growth rate Tesseropa density

16. 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

17. Community Structure Multispecies interactions - Underwood General conclusion - major interactions among all components of system - no keystone species - no links are ‘weak’

18. 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 Habitat amelioration Relative importance high low Stress HIGH RECRUITMENT

19. 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 Habitat amelioration Relative importance Competition high low Stress HIGH RECRUITMENT

20. 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 Habitat amelioration Predation Relative importance Competition high low Stress HIGH RECRUITMENT

21. 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 Habitat amelioration Predation Relative importance Competition Associational defenses high low Stress HIGH RECRUITMENT

22. 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

23. 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

24. 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

25. 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 Habitat amelioration Relative importance Competition Associational defenses high low Stress LOW RECRUITMENT

26. Community Structure Relationship to diversity Diversity high low Stress

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

28. Community Structure Disturbance and Diversity Connell - Intermediate Disturbance Hypothesis Diversity Low High Disturbance (frequency, intensity, extent)

29. Community Structure Disturbance and Diversity Connell - Intermediate Disturbance Hypothesis Competitive dominants fill space Diversity Low High Disturbance (frequency, intensity, extent)

30. 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)

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

32. Models of succession -probably work in different areas