Community Ecology
Chapter 7
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
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
Largest Biodiversity
 Tropical rainforest
 Coral reefs
 Deep sea
 Tropical lakes
 Also considered species rich
 Tropical
dry habitats
 Temperate shrublands (chaparral)
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
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)
Diversity on Islands
 The bigger the more diverse
 The farther from mainland the less
diverse
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
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
Species interaction
 Intraspecific competition – competing
with your own species
 Interspecific competition – competing
with another species
 Compete over food, shelter, space,
breeding, etc.
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))
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)
Black skimmer
seizes small fish
at water surface
Flamingo
feeds on
minute
organisms
in mud
Brown pelican dives for fish,
which it locates from the air
Scaup and other
diving ducks feed on
mollusks, crustaceans,
and aquatic vegetation
Avocet sweeps bill through
mud and surface water in
search of small crustaceans,
insects, and seeds
Louisiana heron wades into
water to seize small fish
Dowitcher probes deeply
into mud in search of
snails, marine worms,
and small crustaceans
Oystercatcher feeds on
clams, mussels, and
other shellfish into which
it pries its narrow beak
Herring gull is a
tireless scarialavenger
Ruddy turnstone searches
under shells and pebbles
for small invertebrates
Knot (a sandpiper)
picks up worms and
small crustaceans left
by receding tide
Piping plover feeds
on insects and tiny
crustaceans on
sandy beaches
Fig. 8.9, p. 182
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
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)
Mutualism
 Two organisms (different species)
interact and both benefit from the
relationship
 Examples
 Clownfish/Anemones
 Tickbird/Rhinoceros
 Protozoan/Termites
Fig. 8.13, p. 187
Commensalism
 Two species interact, one benefits and
the other is unaffected.
 Some trees have mosses or epiphytes
growing on them
Fig. 8.14, p. 187
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
Secondary succession
 Same as primary except in an area that
once had life, but was ruined during a
catastrophe (fire, flood, farming, etc.)
Early Successional
Species
Midsuccessional
Species
Late Successional
Species
Wilderness
Species
Rabbit
Quail
Ringneck pheasant
Dove
Bobolink
Pocket gopher
Elk
Moose
Deer
Ruffled grouse
Snowshoe hare
Bluebird
Turkey
Martin
Hammond’s
Flycatcher
Gray squirrel
Grizzly bear
Wolf
Caribou
Bighorn sheep
California condor
Great horned owl
Ecological succession
Fig. 8.17, p. 190
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
Thank you, have a nice day
You are
here!!