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Today, March 25 th
Begin Module 4
CH 14 Predation/Herbivory
Thursday, March 27 th
CH 14 Predation/Herbivory
CH 15 Parasitism
Due Fri, March 28 th 11:59PM
Quiz 14, 15
> 1
Chapter 14 Learning Objectives
Predation and Herbivory
Predators and herbivores can limit the abundance of
species.
Populations of consumers and consumed populations
fluctuate in regular cycles.
Predation and herbivory favor the evolution of defenses.
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## 2
## 3
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## Consumer -Resource Interactions
> 3
Heterotrophs
Detritivory
Herbivory
Predation
Parasitism
Parasitoids
Hyperparasitoids
1
> species obtain energy by consuming other organisms
How do the other
obtain their energy? Consumer -Resource Interactions
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> 1
## Species interactions may change
## over life stages
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Initially saguaro benefits from
shade of palo verde Eventually competing for
water and nutrients
1Consumer -Resource Interactions:
## Predation
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consumes and kills prey, removes individuals from population
1Herbivores can be predators
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1
consumes and kills prey, removes individuals from population Consumer -Resource Interactions
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## Herbivores can be parasites
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Parasitism
does not kill host directly, consumes part of prey (host)
increases host probability of death, lowers fitness
depends on the extent & duration of the association
1Consumer -Resource Interactions
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## Parasitoids are unique predators
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Parasitoids
do kill their host but only after the parasitoids full development
10% of described insect species are parasitoids
consume the egg/larvae/pupae of other insects
> Cotesia glomerata (wasp) ovipositing in a caterpillar Wasp larvae emerging
1Parasitoids can manipulate host
## behavior
> 12
1
Cordyceps : attack of the killer fungi - Planet Earth Attenborough BBC wildlife
Cordyceps (genus of fungi) manipulate insect host behavior to
increase their own reproductive fitness. Brood parasitism is actually
## parasitoid behavior
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brood parasitism
cuckoos, (& cowbirds) lay eggs in
the nests of other bird species
cuckoo chicks hatch first, eject or
eat host eggs
cuckoo chicks mimic host chick calls
and are fed by host adults
> Eurasian Reed Warbler raising a Cuckoo
1Chapter 14 Learning Objectives
Predation and Herbivory
Predators and herbivores can limit the abundance of
species.
Populations of consumers and consumed populations
fluctuate in regular cycles.
Predation and herbivory favor the evolution of defenses.
## 1
## 2
## 3
> 14 15
Snowshoe hares and
Canada lynx populations
cycle 9 10 years, with lynx
cycles lagging 2 years
behind hare cycles.
2 Predator -Prey cycles
(200 yr dataset) What influences size & stability of
## populations?
> 16
Top -Down Control (predation)
the abundance of a population is limited by its predators
applies to predator -prey & herbivore -plant interactions
Do predators reduce size of prey population below carrying
capacity set by resources for the prey?
2Bottom -Up Control (competition, CH 16)
The abundance of a population is limited by nutrient supply or
by the availability of food.
Do consumer -resource interactions cause population to
fluctuate independent of environmental variation?
> 17
2 What influences size & stability of
## populations? 18
Hare populations increase,
Hypothesis :
2 Top -Down & Bottom -Up Regulation 19
Hypothesis :
2 Top -Down & Bottom -Up Regulation
Hare populations increase, causing food supplies (plants) to decrease.
Starvation, weight loss, and stress may lead to increased predation, all
of which decrease hare populations. Lynx population declines in turn
because hares are less abundant. Plant populations begin to recover.
Start over. 2
Without predators, prey populations reached high numbers.
With predators in a
simple environment,
predator populations
consumed the prey,
and both populations
went extinct.
## Predator -prey cycles in the lab
> 20
Extinction of both populations took longer if oranges were
spread far apart; prey could disperse & it took longer for
predators to find prey. Predator -prey cycles in the lab when
## the environment is complex
2
When experimental design mimicked a metapopulation there
were three population cycles over 8 months.
Stable predator -prey population cycles can be achieved when the
environment is complex so that prey can disperse and hide, and
predators cannot easily find prey.
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## Predator -prey cycles in the lab
2
In 1958, Carl Huffaker conducted experiments using western
predatory mites as predators and six -spotted mites as prey to
understand the conditions that cause predator and prey
populations to fluctuate.
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## Summary
## How do Predator -Prey cycles happen?
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To avoid prey population extinction:
Some prey must be able to disperse/escape/hide
Prey must reproduce faster than predators
To avoid predator population extinction:
Predators must disperse (lowers intra -specific competition)
Switch food source when primary prey not available
224
2Lotka -Volterra:
## Modeling Predator -Prey cycles
> 25
rate of change = population population
of population growth rate decline rate
Lokta -Volterra is a continuous -time model based on
differential equations.
Calculates rate of change in predator and prey populations as
each is influenced by the abundance of the other.
Where have you seen this before?
2Lotka -Volterra:
## Modeling Predator -Prey cycles
> 26
rate of change = population population
of population growth rate decline rate
2
N = number of prey
P = number of predators
c = capture probability (encounter between a
predator and prey leading to the preys capture)
a = assimilation efficiency of a predator converting
consumed prey into predator offspring
m = per capita mortality rate of predators
Prey
Predator A prey population is stable when its rate of change is zero.
A prey population is stable when the addition of prey is balanced
by the consumption of prey.
## Modeling prey
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2
c
Prey population decreases
when the consumption of prey
exceeds prey addition:
Prey population increases when
prey addition exceeds the
consumption of prey: A predator population is stable when its rate of change is zero.
Hence, a predator population is stable when the addition of
predators is balanced by the mortality of predators.
The predator population will increase when the addition of predators
exceeds the mortality of predators:
The predator population will decrease whenever
## Modeling predators
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2Modeling predator -prey cycles
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Equilibrium (zero growth) isocline: the population size of one species
that causes the population of another species to be stable.
For prey, this occurs when and for predators when
As the number of
predators or prey
changes and moves
away from the
equilibrium isoclines,
populations will
increase or decrease.
c
230
Joint population trajectory: the simultaneous trajectory of predator
and prey populations.
Joint equilibrium point: the point at which the equilibrium isoclines
for predator and prey populations cross.
If either of the populations stray
from the equilibrium point, they
will oscillate around the point.
2 Modeling predator -prey cycles
> N
> P
31
2Lotka -Volterra Prediction
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Increase in intrinsic growth rate of prey (r) leads to increase in
predator population (P) but not prey population (N) --- Why?
> dN /dt = 0
> Number of Prey ( N)
c
=
2Predator Prey
## Increase in (r) increases predator
## but not prey populations
> 33
2Lotka -Volterra:
## Simplistic model, valuable tool
> 34
Predicts predator -prey cycles
Predator numbers lag prey numbers
Assumptions:
The prey population finds ample food at all times.
The food supply of the predator population depends
entirely on the prey populations (no switching).
The rate of change of population is proportional to its size.
During the process, the environment does not change in
favor of one species and genetic adaptation is sufficiently
slow. (essentially no evolution)
2Functional response: the relationship between the density of
prey and an individual predators rate of food consumption.
## Functional Response Curves
> 35
2
Type I predator rate of prey consumption
increases linearly with prey density until
satiation.
Type II predator rate of prey consumption
begins to slow as prey density increases and
then plateaus; predators spend more time
handling more prey.
Type III low predator rate of prey consumption
at low prey density; and type II response at
high density for three reasons
prey refugia
poor search image
prey switching Researchers manipulated the
abundance of isopod and mayfly prey
for backswimmer predators.
When mayflies were rare,
backswimmers consumed fewer
mayflies than expected based on their
proportion, which indicates prey
switching.
When mayflies were common,
backswimmers consumed more
mayflies than expected, likely because
the predators had practice consuming
their prey.
## Type III Functional Response is most
## accurate and common
> 36
2Chapter 14 Learning Objectives
Predation and Herbivory
Predators and herbivores can limit the abundance of
species.
Populations of consumers and consumed populations
fluctuate in regular cycles.
Predation and herbivory favor the evolution of defenses.
## 1
## 2
## 3
> 37
2
## How to not get eaten
> 38
Structural Aposematism/Chemical
Crypsis Behavioral 2
Crypsis : camouflage that either allows
an individual to match its environment
or breaks up the outline of an individual
to blend in better with the background
(e.g., katydids, horned lizards).
Structural defenses reduce a predators
ability to capture, attack, or handle prey.
Some prey have defenses that are
phenotypically plastic ; when the crucian
carp detects a predatory fish, it grows
muscle mass that allows it to swim
faster.
## Crypsis and structural defenses
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2
## Chemical defenses
> 40
Warning coloration (aposematism): a strategy where distastefulness
evolves in association with very conspicuous colors and patterns. Mimicry
> 41
## Mimics exploit coevolutionary
## interactions
> 2
## Mimics exploit coevolutionary
## interactions
> 42
Mullerian mimicry: several unpalatable species evolve a similar
pattern of warning coloration; similarity in warning confers
protection
2Batesian mimicry: when palatable species evolve warning
coloration that resembles unpalatable species (e.g., hover flies
and hornet clearwings resemble the common wasp).
> 43
2 Mimics exploit coevolutionary
## interactions
> Common wasp
> (aposematism )
> Hover fly (mimic)
> Hornet clearwing
> (mimic)
2
Defense costs can reduce growth, development, and reproduction.
Many species of ladybugs are red with
black spots, which informs predators
that they contain foul -tasting alkaloids
(aposematism) .
Alkaloids are energetically expensive to
produce.
Only ladybugs that consumed high
amounts of food were able to produce
the aposematic coloration and high
amounts of alkaloids.
## Costs of defenses
> 44
2
Coevolution: when two or more species affect each others
evolution; selection for prey defenses should favor the selection for
counter -adaptation in predators; an evolutionary arms race
The cane toad was introduced into
Australia in 1935.
The toad has skin toxins that cause
predators to become sick or die.
Predators in Australia (e.g., black snakes)
had no experience with these toxins; many
attempted to consume the toad and died.
Black snake populations are evolving
resistance to the toxins; snakes with longer
exposure to toads have more resistance.
## Counter adaptations of predators
> 45
## Evolution of Herbivory
46
Labandeira , C. C., 1997. Insect Mouthparts: Ascertaining the paleobiology of insect feeding
strategies. Annual Review of Ecology and Systematics 28: 153 -193
400+ MYA 300MYA 200MYA 100MYA
2Plant chemical defenses
## (secondary metabolites)
> 47
nitrogen compounds
(e.g., alkaloids >3000)
terpenoids (>10,000)
(e.g., citronella, menthol)
phenolics
(e.g., tannins, flavinoids , lignin)
Tradeoff in investing in growth and
reproduction versus defense.
22
Many plants produce defensive chemicals
at the cost of reduced fitness .
Tobacco plants respond to herbivores by
producing chemicals including nicotine.
Researchers damaged two groups of
tobacco plants but treated one group with
a hormone that blocked nicotine
production.
The group without hormones produced
more nicotine and fewer seeds.
## Defenses against herbivores
> 48
## Coevolution of secondary defense:
## tradeoffs
> 49
> 100 plant families
31 plant families
8 plant families
2 genera!
Dr. May Berenbaum , UIUC
National Academy Fellow
2U.S. President Barack Obama prepares to present Professor May Berenbaum
of the University of Illinois at Urbana -Champaign with the National Medal of
Science in the East Room of the White House November 20, 2014 in
Washington, DC. According to the White House, Brenbaum was awarded the
medal for pioneering studies on chemical coevolution and the genetic basis of
insect -plant interactions, and for enthusiastic commitment to public
engagement that inspires others about the wonders of science." The medals
are the highest honors bestowed by the United States Government for
achievements in science, technology, and innovation.
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2X Files
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