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Predation – one species feeds on another enhancesfitness of predator but reduces fitness of prey
(+/– interaction)
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Types of predators
Carnivores – kill the prey during attack
Herbivores – remove parts of many prey, rarely lethal.
Parasites – consume parts of one or few prey,rarely lethal.
Parasitoids – kill one prey during prolongedattack.
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Diet breadth
consumes only one prey type
consumes many prey types
broad diet
narrow diet
specialist
generalist
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Why are ecological interactions important?
Interactions can affect distribution and abundance.
Interactions can influence evolution.
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How has predation influenced evolution?
Adaptations to avoid being eaten:
spines (cactii, porcupines)hard shells (clams, turtles)toxins (milkweeds, some newts)bad taste (monarch butterflies)
camouflageaposematic colorsmimicry
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Camouflage – blending in
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Aposematic colors – warning
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Is he crazy???
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Mimicry – look like something that is dangerousor tastes bad
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Mimicry – look like something that is dangerousor tastes bad
Mullerian mimicry – convergence of several unpalatable species
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Mimicry – look like something that is dangerousor tastes bad
Batesian mimicry – palatable species mimics an unpalatable species
model
mimic
model
mimics
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Lotka-Volterra models describe predator and preypopulation cycling.
Real world predator and prey populations can cyclein size.
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Keystone species affect community structure
Predators can allow coexistence of competing prey
competitors
Barnacles MusselsBalanus Mytilus (Paine 1966)
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Keystone species affect community structure
Predators can allow coexistence of competing prey
Starfish
competitors
predator Pisaster
Barnacles MusselsBalanus Mytilus (Paine 1966)
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Barnacles MusselsBalanus Mytilus
How can we test the effect of apredator on community structure?
Experiment - Remove the predator
StarfishPisaster
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Removal experiment
time
starfishremoved
%of
inter-tidalzone
mussels
- mussels are the dominant competitor- competitive exclusion of barnacles
barnacles
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time
starfishremoved
%of
inter-tidalzone
mussels
barnacles
What is the effect of the predatoron the structure of this community?
- starfish allow coexistence of competitors
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Barnacles Mussels
StarfishPisaster
Starfish are picky – they prefer mussels (dominant competitor),which allows barnacles (weaker competitor) to coexist.
How do starfish promote coexistence?
Balanus Mytilus