Predation

1
Predation one species feeds on another ?
enhances fitness of predator but reduces fitness
of prey
(/ interaction)
2
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 prolonged attack.
3
Diet breadth
consumes only one prey type
narrow diet
specialist
generalist
broad diet
consumes many prey types
4
Why are ecological interactions important?
Interactions can affect distribution and
abundance.
Interactions can influence evolution.
5
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) camouflage aposematic
colors mimicry
6
Camouflage blending in
7
Aposematic colors warning
8
Is he crazy???
9
Mimicry look like something that is
dangerous or tastes bad
10
Mimicry look like something that is
dangerous or tastes bad
Mullerian mimicry convergence of several
unpalatable species
11
Mimicry look like something that is
dangerous or tastes bad
Batesian mimicry palatable species mimics
an unpalatable species
model
mimic
mimics
model
12
Why are ecological interactions important?
Interactions can affect distribution and
abundance.
Interactions can influence evolution.
13
Lotka-Volterra models describe predator and
prey population cycling. Real world predator
and prey populations can cycle in size.
14
Why are ecological interactions important?
Interactions can affect distribution and
abundance.
Interactions can influence evolution.
15
Keystone species affect community structure

Predators can allow coexistence of competing prey
competitors
Barnacles Mussels
Balanus
Mytilus
(Paine 1966)
16
Keystone species affect community structure

Predators can allow coexistence of competing prey
Starfish
predator
Pisaster
competitors
Barnacles Mussels
Balanus
Mytilus
(Paine 1966)
17
How can we test the effect of a predator on
community structure?
Starfish
Pisaster
Barnacles Mussels
Balanus
Mytilus
18
Removal experiment
- mussels are the dominant competitor -
competitive exclusion of barnacles
starfish removed
mussels
of inter- tidal zone
barnacles
time
19
What is the effect of the predator on the
structure of this community?
- starfish allow coexistence of competitors
starfish removed
mussels
of inter- tidal zone
barnacles
time
20
How do starfish promote coexistence?
Starfish
Pisaster
Barnacles Mussels
Balanus
Mytilus
Starfish are picky they prefer mussels
(dominant competitor), which allows barnacles
(weaker competitor) to coexist.
21
Keystone species affect community
structure disproportionately to their
abundance. Picky predators can promote
coexistence among competing prey
species. Competitive exclusion is prevented when
the dominant competitor is the preferred prey.