Community Ecology

1
Community Ecology

• Chapter 7

2
The flying fox

• Keystone species in tropical rainforest
• Pollinates plants while drinking nectar
• Spreads seed of fruit eaten
• Mutualistic relationship with durian fruit
• Help regenerate open areas through seed dispersal
  (80-90 new seed)
• Decline in numbers from deforestation and hunting

3
Dispersal of diversity

• Groups are arranged either in clumps (most
  common), uniformly, or randomly
• Edge effects are ecotones where different species
  may live. Usually different microclimate than
  adjoining areas

4
Largest Biodiversity

• Tropical rainforest
• Coral reefs
• Deep sea
• Tropical lakes
• Also considered species rich
• Tropical dry habitats
• Temperate shrublands (chaparral)

5
Biodiversity continued

• Most diversity near equator
• Higher availability of resources
• Less evolutionary time
• High diversity leads to higher diversity
• More pressure from disease and parasites
• Speciation higher than background extinction

6
Diversity in marine systems

• Higher diversity near 2000 meters and on bottom
• More stable away from surface
• Lack of nutrients below 2000m
• Abundant nutrient on bottom and variation of
  habitats
• Pollution lowers diversity (never would have
  guessed that)

7
Diversity on Islands

• The bigger the more diverse
• The farther from mainland the less diverse

8
Nonnative species

• Also called alien, exotic and introduced
• Generally have no natural predators so population
  goes unchecked, seriously damaging the ecosystem
• Often introduced by accident
• Cargo from foreign areas
• Pets and house plants that escape
• Natural migration due to climate changes

9
Prime players

• Indicator species serves as an early warning
  that an ecosystem is declining
• Birds low birth rates, thin shells, birth
  defects
• Keystone species a species that contributes
  greatly to an ecosystem even though they may not
  dominate in numbers
• Seed dispersal/pollination (birds)
• Habitat modification (beaver)
• Efficient recycling of matter

10
Species interaction

• Intraspecific competition competing with your
  own species
• Interspecific competition competing with
  another species
• Compete over food, shelter, space, breeding, etc.

11
Dibs, I saw it first!

• Interference competition when two or more
  species try to limit access to a resource (some
  humming birds defend particular trees)
• Exploitation competition when one group uses a
  resource faster than another (can lead to
  competitive exclusion principle (one dies out))

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How to avoid competition

• Resource partitioning using a limited resource
  at different times, in different places or
  different ways
• Think about how similar all birds are, but
  through evolution have developed different
  feeding patterns (beaks)

13
Brown pelican dives for fish, which it locates
from the air
Herring gull is a tireless scarialavenger
Black skimmer seizes small fish at water surface
Dowitcher probes deeply into mud in search
of snails, marine worms, and small crustaceans
Avocet sweeps bill through mud and surface water
in search of small crustaceans, insects, and
seeds
Scaup and other diving ducks feed on mollusks,
crustaceans, and aquatic vegetation
Ruddy turnstone searches under shells and
pebbles for small invertebrates
Flamingo feeds on minute organisms in mud
Oystercatcher feeds on clams, mussels, and other
shellfish into which it pries its narrow beak
Knot (a sandpiper) picks up worms and small
crustaceans left by receding tide
Piping plover feeds on insects and
tiny crustaceans on sandy beaches
Louisiana heron wades into water to seize small
fish
Fig. 8.9, p. 182
14
Predator-Prey relationship

• Needed to keep gene pool strong
• Slow, sick, less agile, etc. weak are more
  easily caught, and are therefore removed from the
  gene pool. This strengthens the remaining
  population

15
Symbiotic interactions

• 3 types of symbiosis parasitism, mutualism, and
  commensalism
• Parasitism one species (parasite) feeds on
  another organism (host) by living in or on the
  host.
• Parasites help promote biodiversity by
  controlling population size (eliminates the weak)

16
Mutualism

• Two organisms (different species) interact and
  both benefit from the relationship
• Examples
• Clownfish/Anemones
• Tickbird/Rhinoceros
• Protozoan/Termites

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Fig. 8.13, p. 187
18
Commensalism

• Two species interact, one benefits and the other
  is unaffected.
• Some trees have mosses or epiphytes growing on
  them

19
Fig. 8.14, p. 187
20
Succession

• Primary succession takes place on new rock or
  lifeless ground
• Mosses/lichen begin to turn rock to soil
• Small fast growing plants take root (weeds)
• Larger plants grow in the nutrient enhanced soil
• Trees immigrate in from birds
• Mature ecosystem (forest) climax community

21
Secondary succession

• Same as primary except in an area that once had
  life, but was ruined during a catastrophe (fire,
  flood, farming, etc.)

22
Early Successional Species Rabbit Quail Ringneck
pheasant Dove Bobolink Pocket gopher
Midsuccessional Species Elk Moose Deer Ruffled
grouse Snowshoe hare Bluebird
Late Successional Species Turkey Martin Hammonds
Flycatcher Gray squirrel
Wilderness Species Grizzly bear Wolf Caribou Bigh
orn sheep California condor Great horned owl
Ecological succession
Fig. 8.17, p. 190
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Sustainability

• What maintains an ecosystem
• Inertia or persistence ability of a system to
  resist disturbances
• Constancy keep population level stable
• Resilience ability to bounce back from a
  disturbance

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