1. Chapter 7
Community Ecology

2. Chapter Overview Questions
What determines the number of species in a community?
How can we classify species according to their roles in a community?
How do species interact with one another?
How do communities respond to changes in environmental conditions?
Does high species biodiversity increase the stability and sustainability of a community?

3. Updates Online
The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at to access InfoTrac articles.
InfoTrac: California's wild crusade. Virginia Morell. National Geographic, Feb 2006 v209 i2 p80(16).
InfoTrac: Traveling green. Carol Goodstein. Natural History, July-August 2006 v115 i6 p16(4) .
InfoTrac: Too hot to trot. Charlie Furness. Geographical, May 2006 v78 i5 p51(7).
The Nature Conservancy: Jaguar Habitat and Center of Maya Civilization Protected in Historic Land Deal
National Geographic News: Conservationists Name Nine New "Biodiversity Hotspots"

4. Core Case Study: Why Should We Care about the American Alligator?
Hunters wiped out population to the point of near extinction.
Alligators have important ecological role.
Figure 7-1

5. Core Case Study: Why Should We Care about the American Alligator?
Dig deep depressions (gator holes).
Hold water during dry spells, serve as refuges for aquatic life.
Build nesting mounds.
provide nesting and feeding sites for birds.
Keeps areas of open water free of vegetation.
Alligators are a keystone species:
Help maintain the structure and function of the communities where it is found.

6. Endangered Species 1967 – American Alligator listed as endangered
By 1977 – reduced listing to threatened
Now there are farms that provide alligator meat and skin
There are invasive species that threaten the alligators: breeding populations of burmese pythons in Florida

7. COMMUNITY STRUCTURE AND SPECIES DIVERSITY
Biological communities differ in their structure and physical appearance.
Figure 7-2

8. Tropical rain forest Coniferous forest Deciduous forest Thorn forest
Figure 7.2
Natural capital: generalized types, relative sizes, and stratification of plant species in various terrestrial communities.
Tropical
rain forest
Coniferous
forest
Deciduous
forest
Thorn
forest
Thorn
scrub
Tall-grass
prairie
Short-grass
prairie
Desert
scrub
Fig. 7-2, p. 144

9. Species Diversity and Niche Structure: Different Species Playing Different Roles
Biological communities differ in the types and numbers of species they contain and the ecological roles those species play.
Species diversity/ species richness
the number of different species it contains
species evenness
combined with the abundance of individuals within each of those species
Do you have equal numbers of different species?

10. The Edges Community structure varies around the edges
How?
Might be sunnier, warmer, drier than forest interior
Increasing edges with habitat fragmentation increases stress on organisms
Species more vulnerable to predators and fire
Can create barriers to colonizing new areas, finding mates and food

11. Species Diversity and Niche Structure
how many potential ecological niches occur?
how they resemble or differ?
how the species occupying different niches interact?
Geographic location:
species diversity is highest in the tropics and declines as we move from the equator toward the poles.

12. TROPIC
Consistent daily climate and reliable food sources results in specialists with narrow niches versus generalists
Species in higher latitudes with variable weather have adaptations that allow them to survive in a greater range of environments

13. TYPES OF SPECIES
Native, nonnative, indicator, keystone, and foundation species play different ecological roles in communities.
Native:
those that normally live and thrive in a particular community.
Nonnative species:
those that migrate, deliberately or accidentally introduced into a community.
Also known as invasive

14. Purposely introducing nonnatives
1957 the African bee was introduced to increase the productivity of honey bees
This introduction created “The killler bees”
They have migrated North but are limited by cold weather.
Theses bees are overly aggressive compared with commercial honey bees

15. CANE TOAD
We will watch a video that discusses the affects of the CANE TOAD introduced in Australia

16. Case Study: Species Diversity on Islands
MacArthur and Wilson proposed the species equilibrium model or theory of island biogeography in the 1960’s.
Model projects that at some point the rates of immigration and extinction should reach an equilibrium based on:
Island size
Distance to nearest mainland

17. Possible Author for Book
E. O. Wilson
Main works
The Theory of Island Biogeography, 1967, Princeton University Press (2001 reprint), ISBN , with Robert H. MacArthur
The Insect Societies, 1971, Harvard University Press, ISBN
Sociobiology: The New Synthesis 1975, Harvard University Press, (Twenty-fifth Anniversary Edition, 2000 ISBN )
On Human Nature, 1979, Harvard University Press, ISBN
Genes, Mind and Culture: The coevolutionary process, 1981, Harvard University Press, ISBN
Promethean fire: reflections on the origin of mind, 1983, Harvard University Press, ISBN
Biophilia, 1984, Harvard University Press, ISBN

18. Success and Dominance in Ecosystems: The Case of the Social Insects, 1990, Inter-Research, ISSN
The Ants, 1990, Harvard University Press, ISBN , Winner of the Pulitzer Prize, with Bert Hölldobler
The Diversity of Life, 1992, Harvard University Press, ISBN , The Diversity of Life: Special Edition, ISBN
The Biophilia Hypothesis, 1993, Shearwater Books, ISBN , with Stephen R. Kellert
Journey to the Ants: A Story of Scientific Exploration, 1994, Harvard University Press, ISBN , with Bert Hölldobler
Naturalist, 1994, Shearwater Books, ISBN
In Search of Nature, 1996, Shearwater Books, ISBN , with Laura Simonds Southworth
Consilience: The Unity of Knowledge, 1998, Knopf, ISBN
The Future of Life, 2002, Knopf, ISBN
Pheidole in the New World: A Dominant, Hyperdiverse Ant Genus, 2003, Harvard University Press, ISBN
From So Simple a Beginning: Darwin's Four Great Books. 2005, W. W. Norton.
The Creation: An Appeal to Save Life on Earth, September 2006, W. W. Norton & Company, Inc. ISBN
Nature Revealed: Selected Writings , Johns Hopkins University Press, Baltimore. ISBN
The Superorganism: The Beauty, Elegance, and Strangeness of Insect Societies, 2009, W.W. Norton & Company, Inc. ISBN , with Bert Hölldobler

19. Indicator Species: Biological Smoke Alarms
Species that serve as early warnings of damage to a community or an ecosystem.
Presence or absence of trout species because they are sensitive to temperature and oxygen levels.
Birds are affected quickly by change
Butterflies are associated with certain plants
Coal miners used to use canaries
If they stopped singing then its time to get out!!!

20. Keystone Species: Major Players
Keystone species help determine the types and numbers of other species in a community thereby helping to sustain it.
How were Yellowstone wolves a keystone species?
Figures 7-4 and 7-5

21. Case Study: Why are Amphibians Vanishing?
Frogs serve as indicator species because different parts of their life cycles can be easily disturbed.
Figure 7-3

22. Adult frog (3 years) Young frog Sperm Tadpole develops into frog
Sexual
Reproduction
Tadpole
Figure 7.3
Typical life cycle of a frog. Populations of various frog species can decline because of the effects of harmful factors at different points in their life cycle. Such factors include habitat loss, drought, pollution, increased ultraviolet radiation, parasitism, disease, overhunting for food (frog legs), and nonnative predators and competitors.
Eggs
Fertilized egg
development
Egg hatches
Organ formation
Fig. 7-3, p. 147

23. Case Study: Why are Amphibians Vanishing?
Frogs sensitive at various stage of life
Eggs absorb UV radiation or pollution
Tadpoles live in water and eat plants
As adults they eat insects (pesticide exposure)
Frogs have thin permeable skin
Easily absorb pollutants from water, air, soil
As of % of populations threatened
43% of populations declining

24. Case Study: Why are Amphibians Vanishing?
See answers on next slide

25. FROGS: No single cause has been indentified
Habitat loss and fragmentation
Draining and filling wetlands, deforestation, development
Prolonged drought: kills tadpoles
Pollution
Pesticides = sensitivity to bacterial, viral and fungal diseases and cause sexual abnormalities
Increases in ultraviolet radiation from ozone layer destruction
Harms embryos of amphibians in shallow ponds

26. Frogs continued Parasistes Viral and Fungal diseases Climate Change:
Chytrid fungus attacks the skin
Climate Change:
Evaporated water increases cloud cover, lowers daytime temps and warms night = chytrid fungi
Overhunting (Frog leg delicacy in Asia and France)
Natural immigration or deliberate introduction of nonnative predators + competitors

27. Why should we care if frogs die?
They signal degradation of habitat
They eat insects
They are genetic storehouse of pharmaceutical products waiting to be discovered
Painkillers, antibiotics, burns, heart disease, etc
They might not need us, but we need them

28. Video: Frogs Galore From ABC News, Biology in the Headlines, 2005 DVD.
PLAY
VIDEO
From ABC News, Biology in the Headlines, 2005 DVD.

29. Foundation Species: Other Major Players
Expansion of keystone species category.
Foundation species can create and enhance habitats that can benefit other species in a community.
Elephants push over, break, or uproot trees, creating forest openings promoting grass growth for other species to utilize.
Bats and birds regenerate deforested areas (how?)
Beavers create wetlands

30. How Would You Vote?
To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment.
Do we have an ethical obligation to protect shark species from premature extinction and treat them humanely?
a. No. It's impractical to force international laws on individual fishermen that are simply trying to feed their families with the fishing techniques that they have.
b. Yes. Sharks are an important part of marine ecosystems. They must be protected and, like all animals, they should be humanely treated.

31. Sharks SENSITIVE TO OVERFISHING Whale shark dorsal fin can = $10,000
Bowl of soup can = $100
Yet fins found to be high in MERCURY
Sharks killed because we fear them, yet only 7 people per year on average die from sharks
SHARKS are our key to cancer.
Sharks rarely get cancer and have effective immune systems
They grow slow, mature late =
SENSITIVE TO OVERFISHING

32. SPECIES INTERACTIONS: COMPETITION AND PREDATION
Species can interact through competition, predation, parasitism, mutualism, and commensalism.
Some species evolve adaptations that allow them to reduce or avoid competition for resources with other species (resource partitioning).

33. Resource Partitioning
Each species minimizes competition with the others for food by spending at least half its feeding time in a distinct portion of the spruce tree and by consuming somewhat different insect species.
Figure 7-7

34. Niche Specialization
Niches become separated to avoid competition for resources.
Figure 7-6

35. Region of niche overlap
Number of individuals
Species 1
Species 2
Region of
niche overlap
Resource use
Figure 7.6
Natural capital: resource partitioning and niche specialization as a result of competition between two species. The top diagram shows the overlapping niches of two competing species. The bottom diagram shows that through natural selection the niches of the two species become separated and more specialized (narrower) so they avoid competing for the same resources.
Number of individuals
Species 1
Species 2
Resource use
Fig. 7-6, p. 150

36. Examples
The lion eats larger animals and leopards eat the smaller animals when both exist in the same habitat.
Hawks hunt by day and Owls hunt the same prey by night.

37. SPECIES INTERACTIONS: COMPETITION AND PREDATION
Species called predators feed on other species called prey.
Organisms use their senses their senses to locate objects and prey and to attract pollinators and mates.
Some predators are fast enough to catch their prey, some hide and lie in wait, and some inject chemicals to paralyze their prey.

38. PREDATION
Some prey escape their predators or have outer protection, some are camouflaged, and some use chemicals to repel predators.
Figure 7-8

39. Camouflage (a) Span worm Fig. 7-8a, p. 153 Figure 7.8
Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior.
(a) Span worm
Fig. 7-8a, p. 153

40. Camouflage (b) Wandering leaf insect Fig. 7-8b, p. 153 Figure 7.8
Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior.
(b) Wandering leaf insect
Fig. 7-8b, p. 153

41. Chemical Warfare (c) Bombardier beetle Fig. 7-8c, p. 153 Figure 7.8
Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior.
(c) Bombardier beetle
Fig. 7-8c, p. 153

42. Chemical Warfare Warning coloration (d) Foul-tasting monarch butterfly
Figure 7.8
Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior.
(d) Foul-tasting monarch butterfly
Fig. 7-8d, p. 153

43. Chemical Warfare Warning coloration (e) Poison dart frog
Figure 7.8
Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior.
(e) Poison dart frog
Fig. 7-8e, p. 153

44. mimicry (f) Viceroy butterfly mimics monarch butterfly
Figure 7.8
Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior.
(f) Viceroy butterfly mimics
monarch butterfly
Fig. 7-8f, p. 153

45. (g) Hind wings of Io moth resemble eyes of a much larger animal.
Figure 7.8
Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior.
(g) Hind wings of Io moth
resemble eyes of a much
larger animal.
Fig. 7-8g, p. 153

46. Deceptive Behavior
Figure 7.8
Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior.
(h) When touched, snake caterpillar changes shape to look like head of snake.
Fig. 7-8h, p. 153

47. SPECIES INTERACTIONS: PARASITISM, MUTUALISM, AND COMMENSALIM
Parasitism occurs when one species feeds on part of another organism.
In mutualism, two species interact in a way that benefits both.
Commensalism is an interaction that benefits one species but has little, if any, effect on the other species.

48. Parasites: Sponging Off of Others
Although parasites can harm their hosts, they can promote community biodiversity.
Some parasites live in host (micororganisms, tapeworms).
Some parasites live outside host (fleas, ticks, mistletoe plants, sea lampreys).
Some have little contact with host (dump-nesting birds like cowbirds, some duck species)

49. Mutualism: Win-Win Relationship
Two species can interact in ways that benefit both of them.
Figure 7-9

50. (a) Oxpeckers and black rhinoceros
Figure 7.9
Natural capital: examples of mutualism. (a) Oxpeckers (or tickbirds) feed on parasitic ticks that infest large, thick-skinned animals such as the endangered black rhinoceros. (b) A clownfish gains protection and food by living among deadly stinging sea anemones and helps protect the anemones from some of their predators. (c) Beneficial effects of mycorrhizal fungi attached to roots of juniper seedlings on plant growth compared to (d) growth of such seedlings in sterilized soil without mycorrhizal fungi.
(a) Oxpeckers and black rhinoceros
Fig. 7-9a, p. 154

51. (b) Clownfish and sea anemone
Figure 7.9
Natural capital: examples of mutualism. (a) Oxpeckers (or tickbirds) feed on parasitic ticks that infest large, thick-skinned animals such as the endangered black rhinoceros. (b) A clownfish gains protection and food by living among deadly stinging sea anemones and helps protect the anemones from some of their predators. (c) Beneficial effects of mycorrhizal fungi attached to roots of juniper seedlings on plant growth compared to (d) growth of such seedlings in sterilized soil without mycorrhizal fungi.
(b) Clownfish and sea anemone
Fig. 7-9b, p. 154

52. (c) Mycorrhizal fungi on juniper seedlings in normal soil
Figure 7.9
Natural capital: examples of mutualism. (a) Oxpeckers (or tickbirds) feed on parasitic ticks that infest large, thick-skinned animals such as the endangered black rhinoceros. (b) A clownfish gains protection and food by living among deadly stinging sea anemones and helps protect the anemones from some of their predators. (c) Beneficial effects of mycorrhizal fungi attached to roots of juniper seedlings on plant growth compared to (d) growth of such seedlings in sterilized soil without mycorrhizal fungi.
(c) Mycorrhizal fungi on juniper seedlings in normal soil
Fig. 7-9c, p. 154

53. (d) Lack of mycorrhizal fungi on juniper seedlings in sterilized soil
Figure 7.9
Natural capital: examples of mutualism. (a) Oxpeckers (or tickbirds) feed on parasitic ticks that infest large, thick-skinned animals such as the endangered black rhinoceros. (b) A clownfish gains protection and food by living among deadly stinging sea anemones and helps protect the anemones from some of their predators. (c) Beneficial effects of mycorrhizal fungi attached to roots of juniper seedlings on plant growth compared to (d) growth of such seedlings in sterilized soil without mycorrhizal fungi.
(d) Lack of mycorrhizal fungi on juniper seedlings
in sterilized soil
Fig. 7-9d, p. 154

54. Mutualism
The microorganisms in our digestive tract and other guts help digest food and benefit from a sheltered habitat with a consistent food supply
Without termites there would not be a decay of cellulose. Termites have bacteria and protozoan that help them breakdown cellulose (tough carbohydrates in plants)

55. Commensalism: Using without Harming
Some species interact in a way that helps one species but has little or no effect on the other.
Figure 7-10

56. EPIPHYTES Some orchids grow in the branches of other trees.
They appear to not harm their host tree.

57. ECOLOGICAL SUCCESSION: COMMUNITIES IN TRANSITION
New environmental conditions allow one group of species in a community to replace other groups.
Ecological succession: the gradual change in species composition of a given area
Primary succession: the gradual establishment of biotic communities in lifeless areas where there is no soil or sediment.
Secondary succession: series of communities develop in places containing soil or sediment.

58. Primary Succession: Starting from Scratch
Primary succession begins with an essentially lifeless are where there is no soil in a terrestrial ecosystem
Figure 7-11

59. Started on new islands, melted glaciers, after volcanic eruptions
Succession is dependent on climate
Lichens
and mosses
Exposed
rocks
Balsam fir,
paper birch, and
white spruce
forest community
Figure 7.11
Natural capital: primary ecological succession over several hundred years of plant communities on bare rock exposed by a retreating glacier on Isle Royale, Michigan (USA) in northern Lake Superior. The details vary from one site to another.
Jack pine,
black spruce,
and aspen
Heath mat
Small herbs
and shrubs
Time
Fig. 7-11, p. 156

60. Secondary Succession: Starting Over with Some Help
Secondary succession begins in an area where the natural community has been disturbed.
Figure 7-12

61. Time Mature oak-hickory forest Young pine forest with developing
Figure 7.12
Natural capital: natural ecological restoration of disturbed land. Secondary ecological succession of plant communities on an abandoned farm field in North Carolina (USA). It took 150–200 years after the farmland was abandoned for the area to become covered with a mature oak and hickory forest. A new disturbance such as deforestation or fire would create conditions favoring pioneer species such as annual weeds. In the absence of new disturbances, secondary succession would recur over time, but not necessarily in the same sequence shown here.
Young pine forest
with developing
understory of oak
and hickory trees
Shrubs
and pine
seedlings
Perennial
weeds and
grasses
Annual
weeds
Time
Fig. 7-12, p. 157

62. Can We Predict the Path of Succession, and is Nature in Balance?
The course of succession cannot be precisely predicted.
Previously thought that a stable climax community will always be achieved.
Succession involves species competing for enough light, nutrients and space which will influence it’s trajectory.

63. ECOLOGICAL STABILITY AND SUSTAINABILITY
Living systems maintain some degree of stability through constant change in response to environmental conditions through:

64. Inertia (persistence):
the ability of a living system to resist being disturbed or altered.
Constancy:
the ability of a living system to keep its numbers within the limits imposed by available resources.
Resilience:
the ability of a living system to bounce back and repair damage after (a not too drastic) disturbance.

65. ECOLOGICAL STABILITY AND SUSTAINABILITY
Having many different species appears to increase the sustainability of many communities.
Human activities are disrupting ecosystem services that support and sustain all life and all economies.