Exploring Community Ecology: Interactions, Niches, and Succession

1. Chapter 53 Community Ecology

2. Community Ecology • The study of the interactions between the species in an area.

3. Community Hypothesis 1. Individualistic 2. Interactive

4. Individualistic Hypothesis • H.A. Gleason • Community as a chance assemblage of species because of similar abiotic requirements.

5. Interactive Hypothesis • F.E. Clements • Community as a linked assemblage of species that function as an integrated whole.

6. Predictions • Individualistic - fuzzy borders • Interactive - sharp borders • Robert Whittaker – tested the two ideas against each other.

8. Results • If abiotic factors form a continuum, then borders are fuzzy. • Individualistic Hypothesis is correct.

9. Comment • Abiotic factors may form sharp borders. • Ex: soil types • Result – the Community may look very much like the Interactive Hypothesis.

10. Interspecific Interactions • Interaction between species. • May be positive, negative, or neutral. • Ex: 1. Coevolution 2. Predation 3. Mimicry 4. Competition 5. Symbiosis

11. When two species have reciprocal evolution to each other. Ex: Flowers and their pollinators. Coevolution

12. Predator and prey relationships. Ex – Lynx and Hares Predation (+/-)

13. Predation • Often results in interesting defenses or adaptations. • Ex: • Plant defenses • Cryptic coloration • Aposematic coloration

14. Cryptic Coloration • A passive defense where the prey is camouflaged against its environment.

15. The use of conspicuous colors in toxic or unpalatable organisms to warn off predators. poison arrow frogs Aposematic Coloration

16. Mimicry • Defense mechanism where the mimic has a resemblance to another species, the model. • Types: • Batesian • Mullerian

17. Batesian Mimicry • Palatable species mimics an unpalatable model. Hawk moth larva Snake

18. Mullerian Mimicry • Two unpalatable species resemble each other. Yellow Jacket Cuckoo Bee

19. Competition • When two species rely on the same limiting resource. • Intraspecific competition usually more severe than Interspecific competition. • Why?

20. Competitive Exclusion Principle • Predicts that two species with the same requirement can not co-exist in the same community. • One species will survive and the second will go extinct.

21. Ecological Niche • The n-hyperspace of requirements for a species. • How a species “fits into” an ecosystem. • Species can not have niche overlap, the Competitive Exclusion Principle

22. Niche Types 1. Fundamental - what a species is theoretically capable of using. 2. Realized - what a species can actually use.

24. Resource Partitioning • A way that species avoid niche overlap by splitting up the available resources. • Ex: Anolis lizards

25. A. distichus A. insolitus

27. Symbiosis • When two different species live together in direct contact. • Types: 1. Parasitism 2. Commensalism 3. Mutualism

28. Parasitism (+/-) • Parasite harms the host. • Parasites may be external or internal. • Well adapted parasites don't kill the host.

29. Parasitic behavior: A female Nasonia vitripennis laying a clutch of eggs into the pupa of a blowfly (Phormia regina)

30. One partner benefits while the other is unchanged. Ex. – Cattle and Egrets Commensalism (+/o)

31. Both partners benefit from the interaction. Ex: Pollinators and flowers Mutualism (+/+) Acacia Tree and Ants

32. Changes in species composition over time. Succession

33. Succession Stages • Sere: unstable stage usually replaced by another community. • Climax: stable stage, self-reproducing.

34. Succession Types 1. Primary 2. Secondary

35. Primary Succession • Building a community from a lifeless area. • Ex: volcanic islands glaciated areas road cuts

36. Comment • The first example of primary succession was worked out on the Indiana Dunes. • Stages: • Open Beach • Beach Grasses • Conifers (Junipers and Pines) • Oaks • Beech-Maple forest (Climax)

37. Secondary Succession • Where a community has been disturbed and the soil is mostly intact. • Ex: • Cutting down a forest • Blow-outs on the Dunes

38. Causes of Succession 1. Autogenic Factors 2. Allogenic Factors

39. Autogenic Factors • Changes introduced by the organisms themselves. • Ex: toxins acids

40. Outside disturbances Ex: Fire Floods Allogenic Factors

41. Prairie Succession in Oklahoma - Stages 1. Annual Weeds 2. Triple-Awn Grass 3. Bunch Grass 4. Climax: Tall-grass Prairie

42. Annual Weed Stage • Lasts 2-3 years. • Very robust growth (1-2 m). • Species: Sunflower Pigweed Lamb's Quarter

43. Annual Weed Stage

44. Annual Weed Stage

45. Annual Weed Stage

46. Annual Weed Stage

47. Triple-Awn Stage • Lasts 10 - 50 years. • Very poor growth (5-12 cm). • Species: Triple-Awn Grass

48. Triple Awn Stage

49. Question • How can Triple-Awn replace the more robust annual weeds?

50. Allelopathy • The release of chemical inhibitors into the environment. • Sunflower: autotoxic • Triple Awn: tolerant