1. Chapter 7
Community Ecology

2. 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

3. 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.

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

5. 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

6. 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.

7. Species Diversity and Niche
Species diversity: combination of:
species richness - the number of different species it contains
species evenness - abundance of individuals within each of those species

8. Species Diversity and Niche Structure
Niche structure: how many potential ecological niches occur, how they resemble or differ, and 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.

9. Species Diversity on Islands
species equilibrium model
at some point the rates of immigration and extinction should reach an equilibrium based on:
Island size
Distance to nearest mainland

10. TYPES OF SPECIES Native Nonnative Indicator Keystone
Foundation species
Play different ecological roles in communities.

11. TYPES OF SPECIES
Native: those that normally live and thrive in a particular community.
Nonnative species: those that migrate, deliberately or accidentally introduced into a community.

12. Invasive species Nonnative (Introduced)
They displace native species
They lower biodiversity
The can adapt very quickly to local habitats
They contribute to habitat fragmentation
They can reproduce very quickly

13. Importation of Species
                                                                         
                                                                         
                                                                         
                                                                         
                                                                         
                                  
                                  
Importation of Species
Ex. The Chinese chestnut had a fungus that spread & virtually eliminated the American chestnut.
Kudzu

14. Keystone Species: Major Players
Keystone species help determine the types and numbers of other species in a community thereby helping to sustain it.
Figures 7-4 and 7-5

15. 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.

16. 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.

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

18. 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

19. Case Study: Why are Amphibians Vanishing?
Habitat loss and fragmentation.
Prolonged drought.
Pollution.
Increases in ultraviolet radiation.
Parasites.
Viral and Fungal diseases.
Overhunting.
Natural immigration or deliberate introduction of nonnative predators and competitors.

20. 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).

21. 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

22. The Fundamental Niche
The fundamental niche of an organism is described by the full range of environmental conditions (biological and physical) under which the organism can exist.
The realized niche of the organism is the niche that is actually occupied. It is narrower than the fundamental niche.
This contraction of the realized niche is a result of pressure from, and interactions with, other organisms.

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

24. 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

25. 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.

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

27. 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

28. (b) Wandering leaf insect
camouflage
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

29. (c) Bombardier beetle Chemical warfare 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

30. (d) Foul-tasting monarch butterfly
Chemical warfare
& warning coloration
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

31. (e) Poison dart frog Chemical warfare & warning coloration
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

32. 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

33. (g) Hind wings of Io moth resemble eyes of a much larger animal.
Deceptive looks
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

34. 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

35. 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.

36. 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)

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

38. (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

39. (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

40. (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

41. (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

42. 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

43. 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.

44. Succession
The process where plants & animals of a particular area are replaced by other more complex species over time.

45. Primary Succession: Starting from Scratch
Primary succession begins with an essentially lifeless are where there is no soil (bare rock). Soil formation begins with lichens or moss.

46. Primary Succession
Primary begins with a lifeless area where there is no soil (ex. bare rock). Soil formation begins with lichens or moss.

47. Hawaii: Local plants are able to rapidly recolonize barren areas
Primary Succession
Primary succession refers to colonization of a region where there is no pre-existing community. Examples include:
Newly emerged coral atolls, volcanic islands
Newly formed glacial moraines
Islands where the previous community has been extinguished by a volcanic eruption
Hawaii: Local plants are able to rapidly recolonize barren areas

48. Primary Succession
A classical sequence of colonization begins with lichens, mosses, and liverworts, progresses to ferns, grasses, shrubs, and culminates in a climax community of mature forest.
In reality, this scenario is rare. Unless there is the formation of a new island or volcanic eruption.
Mature, slow growing trees
Shrubs and fast growing trees
Grasses and herbaceous plants
Mosses and liverworts
Bare rock
and lichens

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

50. 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

51. Secondary Succession
Secondary succession occurs where an existing community has been cleared by a disturbance that does not involve complete soil loss.
Such disturbance events include cyclone damage, forest fires, hillside slips and clear-cutting.
Clear-cutting reduces ecosystem services provided to humans like oxygen, food, and removal of carbon
Cyclone
Forest fire

52. Secondary Succession
Because there is still soil present, the ecosystem recovery tends to be more rapid than primary succession, although the time scale depends on the species involved and on climatic and edaphic (soil) factors.
Mature forest
Young fast growing trees
Shrubs and small trees
Grasses and herbaceous plants
Pioneer community (annual grasses)
Bare land

53. Pioneer Communities
Pioneer community, Hawaii
A succession proceeds in stages, until the formation of a climax community, which is stable until further disturbance.
Early successional (or pioneer) communities are characterized by:
Simple structure, with a small number of species interactions
Broad niches
Low species diversity
Broad niches

54. Climax Communities
In contrast to early successional communities, climax communities typically show:
Complex structure, with a large number of species interactions
Narrow niches with typically large old growth plants.
High species diversity
Climax community, Hawaii
Large number of species interactions

55. Stages
Land – rock  lichen  small shrubs  large shrubs  small trees  large trees

56. Can We Predict the Path of Succession, and is Nature in Balance?
The course of succession cannot be precisely predicted.
Succession involves species competing for enough light, nutrients and space which will influence it’s trajectory.

57. ECOLOGICAL STABILITY AND SUSTAINABILITY
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.

58. 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.