1. Chapter 54
Community Ecology

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

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

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

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

6. Herbivory (+/-) When an organism eats parts of a plant or algae.
Herbivore – may have special adaptations to find their prey.
Plants – may have adaptations to avoid being eaten.

7. Predation/Herbivory
Often results in interesting defenses or adaptations.
Ex:
Cryptic coloration
Aposematic coloration

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

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

10. Mimicry
Defense mechanism where the mimic has a resemblance to another species, the model.
Types:
Batesian
Müllerian

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

12. Müllerian Mimicry Two unpalatable species resemble each other.
Yellow Jacket
Cuckoo Bee

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

14. 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.

15. 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

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

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

19. A. distichus
A. insolitus

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

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

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

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

27. Assignments Read Chapter 54 or 45 in Hillis
Lab – essay practice with animal behavior lab
Chapter 54 – Friday
Productivity Lab report – Mon.
Ts lab report – by final exam

28. Species with large impacts
Some species have larger impacts on a community structure than others.
Ex:
Dominant Species
Keystone Species
Foundation Species

29. Dominant Species
A species that is the most abundant or has the highest biomass in a community.
Has a major effect on a community both biotically and abiotically.

30. Reason for Dominance? Best Competitor?
Best in avoiding predators and disease?
Invasive species may fit the last explanation.

31. Example Chestnuts – used to make up to 40% of the forest.
Lost between because of fungus disease.
Major impact on wood and nut industries.

32. Response Some tree species increased in abundance to fill the gap.
Mammals and birds did OK.
7 species of insects went extinct.

33. Keystone Species
Not a dominant species, but has a major impact in the community structure.
Often a top predator that controls the numbers of other species.
Ex. Sea Otters

35. Foundation Species
Species that cause physical changes in the environment that affect others.
Ex. Beavers, Bison, Black Rush

37. Succession
Changes in species composition over time.

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

39. Succession Types
1. Primary 2. Secondary

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

41. 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)

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

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

44. Autogenic Factors Changes introduced by the organisms themselves.
Ex: toxins, acids

45. Allogenic Factors
Outside disturbances
Ex: Fire, Floods

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

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

48. Annual Weed Stage

49. Annual Weed Stage

50. Annual Weed Stage

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

52. Triple Awn Stage

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

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

55. Triple-Awn Inhibits Nitrogen fixing bacteria species
Result: soil N stays low which stalls succession.

56. Bunch Grass Stage Lasts 20 - 100 years. Good growth (30-50 cm).
Species: Little Bluestem

57. Bunch Grass Stage

58. Succession Causes
Bunchgrass eventually shades out Triple-Awn, releasing the inhibition of the nitrogen fixers.
Result: soil fertility increases, allowing the next group of species to invade.

59. Climax Prairie Stage Lasts centuries if maintained by fire.
High growth (up to 2 meters).
Species: Big Bluestem, Indiana Grass, Switch Grass, Little Bluestem

60. Tall Grass Prairie

61. Question Stages 3 and 4 are the best for cattle grazing.
Normal succession takes years.
Can the time needed for restoring the prairie be decreased?

62. Solution Add more N to soil (NH4+) Seed climax species
Result: prairie in 3-10 years.
Maintain the prairie by burning.

63. Upland, IN Prairie

64. Upland, IN Prairie

65. Upland, IN Prairie

66. Point
If you understand the causes and controlling factors of succession, you can manipulate them.

67. Some points about Succession
The Organisms are changing in the area over time. General pattern is an increase in biodiversity.
The Climate of the area is NOT changing over time.

68. Other Changes
Soil – becomes richer in N, more depth, better water retention etc.
Light – can decrease at ground level because of shading by taller plants.

69. Biogeography
Study of the past and present distributions of individual species and communities.

70. Range Limitations
1. Lack of dispersion. 2. Failure to survive in new areas. 3. Retraction from former range area.

71. Proof
Fossil Evidence
Pollen Studies
Transplant Experiments

72. Islands Special cases in Biogeography.
Must be colonized from other areas.

73. Island Species Factors
Island size.
Distance from mainland.

76. Island Size Small islands hold few species. Why?
Fewer niches available for species to occupy.

77. Distance from Mainland
Closer islands have more species.
Why?
Easier for colonization.

78. Comment Islands tend to have high numbers of Endemic species Why?
Adaptive Radiation and Evolution of new species.

79. Summary Know the various types of interspecific interactions.
Know the Competitive Exclusion Principle and Niche Concept.
Know Species with large impacts.

80. Summary Know some examples and causes of succession.
Know how island communities are shaped.