COMMUNITY ECOLOGY

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SPECIES INTERACTIONS
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ANNOUNCEMENTS

• Final Exam is Friday, Dec. 12th from 6 8 pm in
  LH 2
• Alternative Final is Dec 12th from 330 530 pm
  in LH 1
• Bring Student ID!!!
• Bring 2 pencil(s), eraser
• NO CALCULATORS
• Extended office hours this Monday
• Normal hrs. from 1 2 pm. Bonus hours from 3 5
  pm

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SPECIES INTERACTIONS

• Populations Do Not Exist in Isolation!
• Populations are tightly linked to other
  populations that share the same habitat

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SPECIES INTERACTIONS

• Types of Interactions Between Species
• Neutral relationships (0 0)
• Commensalisms ( 0)
• Mutualism ( )
• Competition (- -)
• Parasitism ( -)
• Predation ( -)

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SPECIES INTERACTIONS COMMENSALISM

• Relationship directly helps one species without
  having effect on other species
• Ex Birds uses trees as roost site
• Birds benefit from tree
• Trees get nothing, but are not harmed

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SPECIES INTERACTIONS MUTALISM

• Beneficial interaction between two species
• Co-exploitation (not altruism)
• Obligatory Mutualism
• Species cant grow/reproduce without the other

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SPECIES INTERACTIONS MUTALISM

• Yucca Plant and Yucca Moth
• Plant only pollinated by yucca moth
• Moth larva can only grow in yucca plant

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SPECIES INTERACTIONS MUTALISM
Mutualism between fish
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SPECIES INTERACTIONS COMPETITION

• Interspecific
• Competition across species
• Occurs when niches overlap
• Niche a set of habitat requirements
• Two species struggle for same resources
• Negatively impacts both species
• Two outcomes
• Coexistence
• Competitive Exclusion

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SPECIES INTERACTIONS COMPETITION

• Intraspecific
• Competition between members of the same species

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SPECIES INTERACTIONS COMPETITION

• Competitive Exclusion
• Occurs when niches overlap completely
• Fierce competition for overlapping resources
• One species drives another towards extinction

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SPECIES INTERACTIONS COMPETITION
One Species Eats Seeds of One Size Range
Number consumed
Seed size
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SPECIES INTERACTIONS COMPETITION
Complete Niche Overlap
Species 1 Strong competitor
Species 2 Weak competitor,
Driven to extinction
Number consumed
Seed size
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SPECIES INTERACTIONS COMPETITION

• Coexistence
• Occurs if niches do not overlap completely
• May lead to suppressed growth and/or reproduction
  
• Species partition/share available resources
• Use same resource in diff ways or at diff times

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SPECIES INTERACTIONS COMPETITION
Partial Niche Overlap competition for seeds of

intermediate size
Species 2
Species 1
Number consumed
Seed size
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SPECIES INTERACTIONS COMPETITION
Competition occurs when organisms compete for the
same resources. These trees are competing for
nitrogen and other nutrients.
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SPECIES INTERACTIONS COMPETITION
Competition occurs when individuals occupy space
and prevent access to resources by other
individuals. The space preempted by these
barnacles is unavailable to competitors.
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SPECIES INTERACTIONS COMPETITION
Competition occurs when an organism grows over
another, blocking access to resources. This large
fern has overgrown other individuals and is
shading them.
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SPECIES INTERACTIONS COMPETITION
Competition occurs when one species produces
toxins that negatively affect another. Note how
few plants are growing under these Salvia shrubs.
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SPECIES INTERACTIONS COMPETITION
Competition occurs when mobile organisms protect
feeding or breeding territory. These red-winged
blackbirds are displaying to each other at a
territorial boundary.
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SPECIES INTERACTIONS COMPETITION
Competition occurs when organisms interfere with
each others access to specific resources. Here,
spotted hyenas and vultures fight over a kill.
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SPECIES INTERACTIONS PARASITISM

• Parasitism
• One organism drains nutrients from another, while
  living on or within it
• Beneficial to parasite
• Negative effect on host organism
• Weaken host ? sterility, decreased fecundity
• Genetic effects
• Sometimes death

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SPECIES INTERACTIONS PARASITISM
Deformed frog limbs due to parasitic infection
by Trematodes
Adult roundworms in the intestine of a pig
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SPECIES INTERACTIONS PARASITISM
Blood fluke in the intestine of a human
833 µm
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SPECIES INTERACTIONS PARASITISM

• Social Parasites
• Manipulate social behavior of another species
• Ex Cuckoo Bird
• Females lay eggs in another species nest
• Cuckoo hatchlings are usually first to emerge
• Ejects other eggs from nest
• Demands food

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SPECIES INTERACTIONS PREDATION

• Predator Prey Interactions

• Prey
• Targets of predators
• Usually killed for food
• Have wide array of mechanisms
• to defend against predation

• Predator
• Animals that feed on other living
• organisms
• Do NOT take residence in or on
• prey

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SPECIES INTERACTIONS PREDATION
Predators can regulate prey populations and/or
reducethem below carrying capacity
BABOON PREY POPULATION
LEOPARD PREDATOR POPULATION
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SPECIES INTERACTIONS PREDATION
Canadian lynx Snowshoe Hare
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SPECIES INTERACTIONS PREDATION

• Co evolution of Predator and Prey Has Resulted in
• Incredible Adaptations
• Camouflage
• Mimicry
• Warning Coloration
• Predator Responses

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SPECIES INTERACTIONS PREDATION

• Camouflage
• A method to escape detection
• Prey blends in with surroundings
• Morphological adaptations
• Patterning
• Coloration
• Behavior

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SPECIES INTERACTIONS PREDATION
PREY CAMOUFLAGE
LEAST BITTERN LOOKS LIKE REEDS
DESERT PLANT LOOKS LIKE ROCK
CATERPILLAR LOOKS LIKE DROPPINGS
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SPECIES INTERACTIONS PREDATION PREY CAMOUFLAGE
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SPECIES INTERACTIONS PREDATION

• Mimicry
• Prey organism deceives predators
• Copy form and/or behavior of another species
• Must resemble dangerous or unpalatable species

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SPECIES INTERACTIONS PREDATION
MIMICRY
INEDIBLE BUTTERFLY (LEFT) IS A MODEL FOR ITS
EDIBLE MIMIC (RIGHT)
STINGING YELLOWJACKET (LEFT) IS MODEL FOR
NONSTINGING and EDIBLE INSECTS (RIGHT)
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SPECIES INTERACTIONS PREDATION
MIMICRY
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SPECIES INTERACTIONS PREDATION

• Warning Coloration
• Prey (usually toxic) sends warning signal
• to predators
• Bright colors and/or conspicuous patterns
• Prey makes little or no effort to conceal its
  presence
• Predators associate distinctive pattern/coloring
  with foul taste or poison

Poison Dart Frog
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SPECIES INTERACTIONS PREDATION

• Methods to Counter Prey Defense
• Predators
• Camouflage
• Clever ways of avoiding repellants

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SPECIES INTERACTIONS PREDATION
PREDATOR RESPONSE
GRASSHOPPER MICE PLUNGECHEMICAL- SPRAYING END
OF BEETLE INTO THE GROUND BEFORE EATING IT
PRAYING MANTIS (PREDATOR) CAMOFLAGUED IN PLANT
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COMMUNITIES
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COMMUNITIES

• Individual
• Population
• Communities
• All populations of species within the same
  habitat
• An assemblage of species that interact with one
  another
• Ecosystem
• Biosphere

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COMMUNITIES

• Factors That Shape A Community
• Geography Physical Features
• Environmental Factors
• Sucessional Stage
• Assemblages of Species
• Resources
• Patterns of Population
• Immigration, emigration, migration

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FACTORS THAT SHAPE COMMUNITIES GEOGRAPHY
PHYSICAL FEATURES

• Latitude Altitude
• Influence precipitation, temperature, and
  species diversity

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FACTORS THAT SHAPE COMMUNITIES GEOGRPAHY
PHYSICAL FEATURES

• Examples
• tropical wet forests
• subtropical deserts
• temperate grasslands
• temperate forests
• boreal forests
• and tundra

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FACTORS THAT SHAPE COMMUNITIESGEOGRAPHY
PHYSICAL FEATURES

• A latitudinal gradient of species diversity
  exists for most taxa
• Diversity decreases from equator to poles

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FACTORS THAT SHAPE COMMUNITIESENVIRONMENTAL
FACTORS

• Environmental Factors Include
• Disturbances Disasters

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FACTORS THAT SHAPE COMMUNITIESENVIRONMENTAL
FACTORS

• Disturbances
• Event that removes
• individuals or biomass
• from a community
• Important management decisions hinge on
  understanding the disturbance regimes of a
  community

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FACTORS THAT SHAPE COMMUNITIESSUCESSION

• Succession
• The recovery and development of communities
  after a disturbance occurs
• A distinct sequence of communities develops as
  succession proceeds

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SUCESSION IN ALASKA
Climax community
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FACTORS THAT SHAPE COMMUNITIESSPECIES
ASSEMBLAGES

• Species That Contribute To Community Structure
• Predators
• Keystone Predators
• Exotic Species

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FACTORS THAT SHAPE COMMUNITIESSPECIES
ASSEMBLAGES

• Keystone Species
• A dominant species that greatly impacts other
  species and dictates community structure

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FACTORS THAT SHAPE COMMUNITIESSPECIES
ASSEMBLAGES

• Robert Paine Keystones
• Intertidal zone (west coast)
• Removed sea stars (Pisaster) from experimental
  plots
• Mussel pop increased, taking over plot
• Seven invertebrate species disappeared

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Keystone predator present
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Keystone predator absent
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FACTORS THAT SHAPE COMMUNITIESSPECIES
ASSEMBLAGES

• Conclusions Regarding Keystone Species
• Removal of sea stars? decreased community
  diversity (15 ? 8 species)
• Mussels are strongest competitor when sea stars
  absent
• Sea star predation prevents competitive exclusion
  by mussels

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FACTORS THAT SHAPE COMMUNITIESSPECIES
ASSEMBLAGES

• Exotic Species
• Successfully take up residence in places other
  than historical range
• Locally
• European Starling (1890)
• Kudzu Vines (late 1800s, Japan)

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FACTORS THAT SHAPE COMMUNITIESSPECIES
ASSEMBLAGES

• Exotic Species
• European Rabbits (1859)
• British settlers in Australia introduced 24 wild
  European rabbits
• One hundred
• years later ?
• there were
• 200-300 million

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COMMUNITY STABILITY

• Two Views of Community Dynamics Exist
• Communities are stable, orderly, and predictable
• Communities are neither stable nor predictable,
  but a matter of chance
• Historical and experimental data support the
  latter

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COMMUNITY STABILITY

• Many Communities
• Are Easily Destabilized
• Human activity is one destabilizing force
• Humans permanently alter community structure
• Pollution environmental damage
• Ex Changes in climate
• Deforestation development
• Ex Species extinction