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Predation – one species feeds on another enhancesfitness of predator but reduces fitness of prey

(+/– interaction)

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.

Diet breadth

consumes only one prey type

consumes many prey types

broad diet

narrow diet

specialist

generalist

Why are ecological interactions important?

Interactions can affect distribution and abundance.

Interactions can influence evolution.

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

Camouflage – blending in

Aposematic colors – warning

Is he crazy???

Mimicry – look like something that is dangerousor tastes bad

Mimicry – look like something that is dangerousor tastes bad

Mullerian mimicry – convergence of several unpalatable species

Mimicry – look like something that is dangerousor tastes bad

Batesian mimicry – palatable species mimics an unpalatable species

model

mimic

model

mimics

Lotka-Volterra models describe predator and preypopulation cycling.

Real world predator and prey populations can cyclein size.

Keystone species affect community structure

Predators can allow coexistence of competing prey

competitors

Barnacles MusselsBalanus Mytilus (Paine 1966)

Keystone species affect community structure

Predators can allow coexistence of competing prey

Starfish

competitors

predator Pisaster

Barnacles MusselsBalanus Mytilus (Paine 1966)

Barnacles MusselsBalanus Mytilus

How can we test the effect of apredator on community structure?

Experiment - Remove the predator

StarfishPisaster

Removal experiment

time

starfishremoved

%of

inter-tidalzone

mussels

- mussels are the dominant competitor- competitive exclusion of barnacles

barnacles

time

starfishremoved

%of

inter-tidalzone

mussels

barnacles

What is the effect of the predatoron the structure of this community?

- starfish allow coexistence of competitors

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