INTERSPECIFIC
INTERACTIONS
A community is made
up of populations of
different species, or
animals, plants, fungi,
and bacteria, living in
the same area.
Species interactions form
the basis for
many ecosystem
properties and
processes such as
nutrient cycling and food
webs.
•Interspecific interactions are
interactions among organisms ofdifferent
species.
TYPES OF INTERSPECIFIC
Effect on
Species 1


Neutralism
 Competition
 Commensalism
 Amensalism
 Mutualism
 Predation,

 Parasitism,
 Herbivory
INTERACTIONS
0
+
+
-
+
+
Effect on
Species 2
0
0
0
+
+
-
NEUTRALISM


Neutralism the most common type of interspecific
interaction. Neither population affects the other. Any
interactions that do occur are indirect or incidental.
Example:

i. the tarantulas living in a desert and the cacti
living in a desert

ii. salmon and dandelions living in a coastal inlet.
The Domino Effect
• Species do not always influence other species
directly.
•
Interactions between species are often indirect
in nature, such that a change in one species
causes a chain reaction throughout an
ecosystem.
•
It is for this reason that neutralism is rarely
found in nature.
COMPETITION
Competition occurs when organisms in the same community seek
the same limiting resource.
This resource may be prey, water, light, nutrients, nest sites, etc.
Competition among members of the same species is
intraspecific.
Competition among individuals of different species is
interspecific.
Intraspecific competition occurs when two or more individuals of the same
species simultaneously demand use of a limited resource (Wilson, 1975).
Access to this resource is commonly established through agonistic
behavior that rarely takes the form of direct fighting.
Competitors instead resort to displays—conspicuous and exaggerated motor
patterns that demonstrate the displaying individual's ill ease due to the
presence of another and its capacity to inflict harm should the competitor
remain.
The signaler consequently gains an advantage if the recipient heeds the
message and withdraws (Burghardt, 1970).
If two white sharks Carcharodon carcharias attempt to feed on the
same prey, it would be disadvantageous for one to discourage the other
from further feeding by biting it and inflicting a wound.
Because the situation is reciprocal–the individual inflicting the bite this
time may receive it next. Such an injury might reduce either shark's
future ability to catch prey.
For this reason, displays evolve among animals such as sharks.
•Hunched, tense
•Displaying shark
•Displays are graded
proportionally in
response to the
perceived severity of
the threat or conflict
posture
•Arched back
•Raised snout
•Exaggerated,
bilateral depression
of both pectoral fins
•Contorted posture
•Gill billowing
•Jaw gaping
•Jerky, rapid
movements
•Exaggerated
swimming patterns
• Body rolling or
spiral looping
• Stiff movements
Competition: Whenever two niches overlap,
competition ensues between organisms.
Ecological niche:The role that an organism plays in nature is
called ecological niche.
For an animal, that niche includes things like its behavior, the
food it eats, and whether it is active at night or in the day.
For a plant, it includes how much direct sunlight it can
tolerate and the sort of soil on which it thrives.
An ecological niche can be thought of in terms of
competition.
The fundamental niche is the set of resources and
habitats an organism could theoretically use under
ideal conditions.
This ideal niche would exist in the absence of
competition from other species .
The realized niche is the set of resources and
habitats an organism actually used: it is generally
much more restricted due to interspecific competition
(or predation.)
•The overall effect of interspecific competition is
negative for both species that participate (a -/interaction).
•That is, each species would do better if the other species
weren't there.
•Under conditions of limited resources, can:
•two organisms with exactly the same niche can't survive
in the same habitat (because they compete for exactly the
same resources, so one will drive the other to extinction).
•However, species whose niches only partly overlap may
be able to coexist. Also, over long periods of time, they
may evolve to make use of more different, or less
overlapping, sets of resources.
•2 sp exist together or one will displace the other?
Intraspecific competition is density dependent and may
cause density-dependent mortality.
At low densities no intraspecific competition exists and
competition for resources does not play a role in survivorship.
As densities increase, a threshold is reached where density
begins to influence mortality through resource availability.
Competition
Interference (adapted)
competition
Exploitation (contest)
competition.
TYPES OF COMPETITION
Exploitation competition/resource use type occurs when
consumption of a limiting resource by one species makes
that resource unavailable for consumption by another.
one group or individual uses so much of a resource that others
cannot use it. For example, a growing wolf population could
eat the whole food supply of other carnivores..
Competitors can avoid each other by using the resource at
different levels, places, or times.
Trees vying for the same nutrients and sunlight, with one
eventually crowding out the other, and different types of fish
competing for the same territory.
Temporal separation of exploitative competitors
For example, sparrows feed on seeds during the day while kangaroo rats feed at
night. Thus, these two species can compete exploitatively even though they never
come into direct contact with each other.
Similarly, if a plant only produces its seeds in the Autumn, then an insect species that
is active at that time of year will consume resources that are not available to another
insect species that is only active in the spring.
Thus, exploitative competition can occur between species that are not even
alive at the same time.
chap08 Competition and coexistence
Because organisms can consume resources at different times of the year or different
times of the day, it is possible for two species that are not present in the same time and
place to compete exploitatively.
Interference competition
occurs when individuals interfere with the foraging, survival, or reproduction of
others, or directly prevent their physical establishment in a portion of a habitat.
Resources defended
Intraspecific competition
between members of the
same species.
Resource competiton:
each caterpillar chews
as much leaf as it can
Interference competition:
Each caterpillar
physically intimidates the
others
Interspecific competition
between different species.
Aphid sucking
leaf sap
Fig.8.2 the different
types of competition
in nature
Caterpillar
chewing leaf
chap08 Competition and coexistence
21
Whether by interference or exploitation, over time a superior
competitor can eliminate an inferior one from the area, resulting
in competitive exclusion
Traits to win exploitative competition
Natural selection has produced a number of traits that help species win in
exploitative competitive interactions.
For example, because sunlight reaches taller plants first, forest trees are able to
"consume" light before it reaches the understory plants.
Thus, exploitative competition for light favors taller plant growth forms.
Similarly, water infiltrates from the surface down into the soil. Thus, some species
of plants have wide-spread shallow root systems that allow them to pick up water
before it reaches the roots of species with deeper root systems.
The Competitive Exclusion Principle
Early in the twentieth century, two mathematical biologists, A.J.
Lotka and V. Volterra developed a model of population growth to
predict the outcome of competition.
This model relates the population density and carrying
capacity of two species to each other and includes their overall
effect on each other.
Their models suggest that two species cannot compete for the
same limiting resource for long. Even a minute reproductive
advantage leads to the replacement of one species by the other.
This is called the competitive exclusion principle or Gause’s
rule
EXCLUSION
• Paramecium. caudatum is
larger than P. aurellia, but has a
slower reproductive rate. Both
species consume bacteria.
The phenomenon of • Gause grew each species
alone, in a culture where a fixed
competitive exclusion
amount of food (bacteria) was
was first documented
added each day.
experimentally by the
• He then grew the two species
Russian biologist
together.
C. F. Gause.
His result was
the exclusion of
P. caudatum by
P. aurellia.
He hypothesized that the two
species compete for the same
food- P. aurellia is ultimately
able to multiply under
conditions where P. caudatum
can no longer gain enough
energy to divide.
This is called
competitive
exclusion
The Paradox of the Phytoplankton: Why do we
have so many species
“The problem that is presented by the phytoplankton is
essentially how it is possible for a number of species
to coexist in a relatively isotropic or unstructured
environment all competing for the same sorts of
materials.” –G.E. Hutchinson, 1961
Hutchinson noticed that nearby temperate lakes harbored a large number of
phytoplankton species, but was having trouble reconciling this observation with
the emerging concept of competitive exclusion.
Competition theory predicted that when a group of species all compete for the
same resource, eventually the most effective competitor dominates the resource
and drives all the other species in the system to extinction.
In relatively stable systems with few resources (such as Hutchinson’s lakes),
competitive exclusion was expected to be especially swift, yet here were
dozens of coexisting phytoplankton species.
Hutchinson’s greatest and most enduring insight is the idea that different
species are favored under different sets of environmental conditions,and if
the environment changes sufficiently through time, no single competitor
could remain superior long enough to exclude other species.
HOW IS BIODIVERSITY OF LIFE MAINTAINED
(I.E., WHY DO SO MANY SPECIES COEXIST)
Complete Competitors Cannot Coexist
• Competitive exclusion principle states:
• Two species cannot exist on the same limiting resource
(resource if they use it in the same way) indefinitelyultimately, even a slight reproductive advantage to one of
them will result in their displacing the other.
• In terms of the niche-if the niches of two species overlap
completely, only the superior competitor can survive.
• If ecologically similar species compete with one another
for limiting resources, what stops the best competitor
from out-competing all the others- maintenance of
biodiversity?
• The answer may lie in species specializing in their use of
resources and thereby limiting their competition with
others.
Dividing the Resource Pie
Resource Partitioning – differentiation of niches to allow similar species to
coexist in a community (space, behavior, temporal)
Niche partitioning is an important mechanism that organisms use to try to
reduce exploitative competition.
Competition can be reduced if species with similar feeding strategies each
specialize in slightly different resources, feed in different location, or feed at
different times.
For example, beetles that feed on the phloem of trees may feed at different
locations (the roots tips, the root collar, the trunk).
Likewise, ant species
that forage for caterpillar prey may do so at different times of day.
EXAMPLE OF COMPETITIVE
EXCLUSION

Aphytis vs. Aphytis
The California red
scale insect attacks
citrus trees.
It is a serious
economic pest in
Southern
California, and has
evolved resistance
to pesticide.
Adults live under
waxy sheaths, and
are protected from
many generalist
predators as well
 Parasitoids
of the genus Aphytis
attack scale insects
Aphytis chrysomphai was accidentally
introduced to CA.

Despite imposing severe mortality, it did not
control the population-especially in dry valleys.
A linganensis was introduced from China in
1950.

It replaced A. chrysomphai within a decade-its
higher reproductive rate may have been a factor .
In interior valleys, scale insects were still a
problem

Cold temps kill A. linganensis.
Example of Coexistence via Niche Partitioning
A
cold tolerant species, A.
melinus was introduced from
Pakistan in 1957
A. melinus quickly spread throughout
the valleys, but did not displace
A.linganensis from coastal regions.
The two species coexist today,
providing very good protection
against red scale-they have
partitioned the habitat based on
winter temperatures.
EXAMPLE OF RESOURCE PARTITIONING
 One
of the best known cases of resource partitioning
occurs among Caribbean anoles.
As many as five different species of anoles may exist
in the same forest, but each stays restricted to a
particular space: some occupy tree canopies, some
occupy trunks, some forage close to the ground.
When the brown anole was introduced to Florida from
Cuba, it excluded the green anole from the trunks of
trees and areas near the ground: the green anole is now
restricted
to the canopies of trees:the resource
(space, insects) has been partitioned among the two
species
RESOURCE
PARTITIONING

“Peace
treaties”among
different sp. Of
Anolis lizards
Shorebirds with long bills probe for
invertebrates; shorebirds' varied bill
lengths and feeding methods result
in the separation of ecological
niches.
Bees swarming about on ligustrum
during the day.
Moths on the same
ligustrum atnight.
Resource Partitioning
Blakburnian Black-throated Green Cape May
Warbler
Warbler
Warbler
Bay-breasted
Warbler
Yellow-rumped
Warbler
Each species minimizes competition for food with the others by spending at
least half its feeding time in a distinct portion (shaded areas) of the spruce
trees, and by consuming somewhat different insect species.
EXAMPLE OF INTERFERENCE
COMPETITION

The confused flour beetle, Triboleum confusum, and
the red flour beetle, Triboleum castaneum cannibalize
the eggs of their own species as well as the other, thus
interfering with the survival of potential competitors.

In mixed species cultures, one species always
excludes the other. Which species prevails depends
upon environmental conditions and the relative
numbers of each species at the start of the
experiment.
Tribolium
Competition
• Thomas park worked on
competition in two closely
related species of flour beetles,
Tribolium castaneum and
Tribolium confusum.
– Both species infest stored
flour products.
– This is a very challenging
environment, with unlimited
carbohydrates, but limited
protein and extremely
limited moisture.
• When cultures were started with equal
numbers of founders from each species;
– T. castaneum always displaced T. confusum
under moister, or warmer conditions.
– T. confusum always displaced T. castaneum
under colder, or drier conditions.
• In the case of flour beetles, both species
compete strongly for moisture, and one of the
most important mechanisms for competition is
egg cannibalism.
– The larvae of both species eat the eggs of their own
species, as well as the other.
– This is a form of interference competition which
exerts very strong interspecific and intraspecific
effects.
– Different strains differ in their propensity for
cannibalism-and thus differ in competitive ability
• kin selection on some strains has actually decreased
cannibalism-decreasing their competitive ability in mixed
cultures
Impacts of Competition
Species B
Impacts of Competition
Species B
Performance competition in Plants
•No limiting resources
•Reproductive fitness
Most attractive flowers
Seed dispersal-competition between
species can be determined by which one
creates the most seeds and has the best
method of dissemination
.
Head-to-head competition due to
overcrowding, limiting resources
•Offense
•Defense
Offense
•Roots-water, nutrients
•Sunlight
•Resources extremely limitedmost efficient competitor survives
Defense
Allelopathy
For example, the
sage plant, Salvia
leucophylla, secretes
.
toxins
Interference with chemicals(Allelopathy)
• Black walnut trees.
•Hydrojuglone
O2
allelotoxin
Roots, decomposing leaves and
twigs all release juglone into the
surrounding soil
Growth
inhibitory to
Solanaceae,
Pines etc
Character displacement
Character displacement = competing species diverge in their physical
characteristics
Due to the evolution of traits best suited to the resources they use
Results from resourcepartitioning
Two species of finches that live on two different Galapagos Islands have
similar beaks, both suited for using the same food supply. On a third
island, they coexist, but due to evolution, the beak of each bird species is
different. This minimizes competition by enabling each finch to feed on
seeds of a differentsize.
Competition is reduced when two species become more different
CHARACTER DISPLACEMENT-BODY CHANGES AS A
RESULT OF RESOURCE PARTITIONING
•When the two species occur together, G.
fuliginosa has a much narrower beak that
G fortis.
•Sympatric populations of G fuliginosa
eats smaller seeds than G fortis: they
partition the resource.
•When found on separate islands, both
species have beaks of intermediate size,
and exploit a wider variety of seeds.
•These inter-population differences might
have evolved in response to interspecific
competition.
Character displacement refers to the phenomenon
where differences among similar species whose
distributions overlap geographically are accentuated in
regions where the species co-occur but are minimized
or lost where the species’ distributions do not overlap.
This pattern results from evolutionary change driven
by competition among species for a limited resource.
 The rationale for character displacement stems from
theCompetitive Exclusion Principle, which contends
that to coexist in a stable environment two competing
species must differ in their respective ecological
niche; without differentiation, one species will
eliminate or exclude the other through competition.
Foraging habits are another way that organisms can avert
competing with eachother.
A red-tailed hawk is a generalist predator; they eat anything
from rodents to reptiles to other birds. They are good
competitors with other birds of prey because they consume a
wide variety of prey so their options are many.
Specialist predators, however, like the osprey, which eats
strictly fish, are limited in their prey selection as well as their
geographic range because they have to live in areas where their
prey resides.
•Take two similar animals then that inhabit the same
geographic area and eat the same type of food…what
then?
•Herbivorous rhinos deal with this conundrum by
consuming different parts of plants.
•White rhinos have flat, wide lips for grazing grasses
while black rhinos have pointed, dexterous lips for
browsing shrubs.
Plants do not only compete for sunlight. In desert ecosystems,
where water is scarce, the cactus plants do not grow very close
together. Their roots, however, radiate out from the cactus plant, just
under the surface of the soil. The roots of a cactus need to absorb as
much water as possible when it rains. In this ecosystem it is the
roots of the cactus plants which compete for space below the
ground.
To avoid competition with their offspring, plants use animals, wind
and other mechanisms to disperse their seeds or spores away from
the parent plants. Even so, plants normally produce a large number
of seeds or spores to make certain that at least a few of them will
germinate and grow into mature plants.
•Competition as a Regulator
•When two organisms or populations compete with each other,
whether it be directly or indirectly, one of several outcomes can
be expected.
•In extreme cases one population (or individual) out-competes
the other and the ‘losing’ organism becomes extinct from the
area.
•If, however, the competition event is spread over time and the
losing animal has time to respond and recover, they may
relocate to another geographic area (emigrate).
•If the losing organism is not displaced, it may change its
behavior or requirements to utilize different resources so that it
is no longer in competition with its opponent.
•Intraspecific competition can serve as a
regulator for population size.
•If a particular source of prey, or abiotic
habitat feature is not readily available, then
competition for the ones that are will be
heavy.
•If the requirements are scarce enough, this
will cause the population to remain stable, or
decrease.
•If resources are readily available, then
competition will be low and a population
may increase.
•Foreign Contenders
•Sometimes competition can have a serious impact on an
ecosystem, especially when invasive or exotic species
are involved.
•When non-native organisms colonize a new area, they
are sometimes better suited to compete with native
organisms for resources.
•Once able to overcome the transition of the relocation,
they can become very successful and out-compete native
organisms, causing their populations to decline, or in
extreme cases, become locally extinct.
AMENSALISM
 Amensalism
is when one species
suffers and the other interacting
species experiences no effect.
 It is a 0/- relationship
 Eg.
Trees falling into the oceans
during storms
EXAMPLES OF AMMENSALISM
EXAMPLES OF AMMENSALISM
Positive interactions:
Commensalism, Cooperation and
Mutualism
Mutual Aid:A factor
of evolution,
published by Russian
Prince Kropotkin
Commensalism
•Ant colonies harbor rove beetles as commensals. These
beetles mimic the ants behavior, and pass as ants. They eat
detritus and dead ants.
•Anemonefish live within the tentacles of anemones. They
have specialized mucus membranes that render them
immune to the anemone’s stings. They gain protection by
living in this way.
COMMENSALISM
 The
effect of the interaction on population
growth and individual survival is:
LIVINGALONE
A
B
LIVING TOGETHER
A
B
COMMENALISM
0
0
+
0
(The COMMENSAL (A) does better when the host is
present. The HOST (B) is not affected by the
interaction.)
NURSE PLANT
•Established canopy
•Refuge from physical
stress
•Refuge from
predation- physical
sheilding or
Nurse log harboring
a western hemlock tree
unpalatable nurse
plant.
•Refuge from
competition- nurse
logs
Shift from Commensalism to Competition
•Improved resource
availability –dry
Phoresy
Biological hitch-hiking in
which
one organism benefits
through access to a mode
of transportation while the
animal providing this
service is not significantly
affected by itsrole.
Fur adhering Fruits of
Burdock
MITES ON HUMMINGBIRD
BEAKS
FLOWER MITES ON
BEES
MUTUALISM (+/+)
Mutualism
in an interspecific
interaction between two species that
benefits both members.
Populations of each species grow,
survive and/or reproduce at a higher
rate in the presence of the other
species.
ANT-ACACIA MUTUALISMS
ANT-ACACIA MUTUALISMS
Acaciashelter and
food
Ant-defence against
i. herbivory, ii. competition
EXAMPLE OF MUTUALISM
The ants also
clear an area
around the tree
of competing
vegetation.
 Without the ants,
the acacia tree
cannot compete
with other trees.

Leafcutter ants: a complex mutualism
http://bio.kuleuven.be/ento/photo_gallery.htm
http://www.wildernessclassroom.com
Currie et al. 2006 Science
Leaf cutter ants
Mutualism in Lichens
•Mycobiont•Protection and
anchorage to the
algae
•also gather
moisture and
nutrients from
the environment
Photobiont
provides energy
through
photosynthesis.
Mutualism
Corals and Zooxanthellae
ZooxanthellaeUnicellular yellow-brown algae
which live in the corals
•Provide the corals with
carbohydrates via photosynthesis.
•In return, they receive a relatively
protected habitat from the body of
the coral.
Mutualism : Rhizobium and legumes
•When the encounter root hairs of a legume plant they form a mutualism in which “nodules”are
formed.
•Within these nodules,the bacteria can “fix” gaseous nitrogen to ammonia.
•Bacteriahavethe nitrogenaseenzymeallowingthemto fix atmosphericnitrogen(N2)into biotically. availableaminoacids.
•Plants provide the bacteria with fixed carbon from photosynthesis thathelps fuel the fixation process,
and in turn plants receive availablenitrogen.
Mycorrhizae
Endomycorrhizae
Ectomycorrhizae
•The hyphae of the mycorrhizal fungi extend out from the roots,
increasing the capacity of the plant to harvest nutrients from the
environment.
•These relationships are often associated with poor growing
Honeyguide bird and the honey
badger (ratel)
– The bird finds honey
bee nests and makes
a special call to attract
the badger, who
breaks open the hive
so both can eat
– video
FACULTATIVE VS. OBLIGATE
MUTUALISMS
Facultative :Cleaner fishes
Benefits to client: Removal of parasites = better health
Benefits to cleaner: Protection (since clients may guard cleaners
from other predators
Obligate :Pollinators and
flowers
Without pollinators, many insect-pollinated plants
would go extinct due to lack of fertilization.
U.S. Lists a Bumble Bee Speciesas
Endangered
•Bumble bees, are essential
pollinators of wildflowers
and about a third of all U.S.
crops, from blueberries to
tomatoes
•pesticides pollution
A rusty patched bumble bee (Bombus affinis)
Honey ants and aphids
•Facultative to obligate
•Species of aphids that
have lost the ability to
excrete in the absence
of this stimulation.
Provide protection to the aphids from
predation, particularly by ladybirds, and in
some instances will even go so far as to
destroy ladybird eggs
Negative Interactions
Predators
•Negative, direct food related interspecific interaction between
two species in which larger species called predator attacks, kills
and feeds on the smaller species called prey.
•Predator population adversely affect the growth and survival of
smaller prey population and therefore predation is considered an
antagonistic interaction.
•Examples:
•i) There are certain carnivorous plants also referred, as
insectivorous plants that act as predators in nature. Plant like
Nepenthes (pitcher plant), Drosera (sundew), Venus fly trap etc.
feed on insects to fulfil their nitrogen requirement.
ii)All carnivorous animals and scavengers are
predators.
Some predators (such as frog) act as prey for others
(snake) which in turn are prey to a higher carnivores
(eagle).
iii)Herbivorous animals, eating plants or seeds, are
also predators as they feed on individuals or future
individuals.
Significance of Predation
a)Local species diversity is directly related to the efficiency with
which the predators prevent the monopolization of an environmental
area by any species.
b) Predation keeps the prey population under check, so as to maintain
an ecological balance.
c)Weak and less efficient members in the prey population are
removed.
d) Most important significance is in the practical utility of prey
predator relationship on biological control of weeds and pests.
Many insect pests are kept under check by introducing their predator
into the area.
For e.g., Opuntia, which become a serious problem in Australia was
brought under control by introducing its natural herbivore Cactoblastis
(cochineal insects).
Parasitoids
- lay eggs on or in prey and then eggs hatch and
developing offspring consume the prey
Parasitoid wasp attacking moth caterpillar
Predation and Adaptation
•Predation influences the fitness of
both predators and prey.
•Genetically-determined traits that
improve an organism’s ability to
survive and reproduce will be
passed on to its offspring.
•Traits associated withimproved
predation for predators and
escaping predation for prey tend to
be positively selected by natural
selection.
•Predation is a strong, selective
pressure
•Over evolutionary time, prey
organisms have developed a
stunning array of strategies to avoid
12. The Lynx and the Snowshoe
hare
This is the most common example of the predator prey
relationship.
13. Prey Adaptations – Snowshoe
Hare
The snowshoe hare lives in northern parts of North America.
How is it adapted to the cold and to avoid being eaten by
predators, such as lynxes?
Coat changes colour
with the seasons from
greyish-brown in summer
to white in midwinter.
Large ears help to
detect predators.
Strong teeth are able to
chew bark and twigs.
Large back feet spread
out to act as snow shoes.
Fur on the soles also
protects from thecold.
14. Predator adaptations – the lynx
Lynxes are adapted to life in a cold climate. How are these
predators adapted for catching the snowshoe hares that are
their main prey?
Excellent eyesight and
hearing for detecting prey.
Very sharp teeth – prey
watch out!
Thick furry coat protects
from the cold.
Very strong hind leg
muscles are capable of a
pounce 6.5 metres long!
Extra large paws act as
snow shoes on soft,
deep snow.
Tactics of the Predator
Invisibility Cloak (cryptic coloration/
camouflage)
Tactics of the Predator
Death by Poisoning
(Venoms)
Tactics of the Predator
“Right this Way Please”: trap-doors, nets, and other deadly
devices.
Golden orb weaver (nephila
clavipes)
Bees seemed least able to
effectively associate yellow
pigmented webs with danger
•Species such as Argiope argentata employ
prominent patterns in the middle of their webs,
such as zigzags.
•These may reflect ultraviolet light, and mimic
the pattern seen in many flowers known
as nectar guides.
•Spiders change their web day to day, which can
be explained by bee's ability to remember web
patterns.
•Bees are able to associate a certain pattern,
meaning the spider must spin a new pattern
regularly or suffer diminishing prey capture.
Tactics of the Predator
Bigger, Badder,
Faster
200 mph
700 lbs & built to kill
What immortal hand or eye
Could frame thy fearful symmetry?
William Blake
http://www.youtube.com/watch?v=DWsN63PRCW8
17,000 lbs, and perhaps as smart as you
Prey Adaptations – General
Prey have adaptations to detect and prevent being eaten by
predators.
venomous coral snake
mimicry
scarlet kingsnake
speed &
keen senses
camouflage
(cryptic
coloration)
warning
colors &
patterns
•Animals can use speed as a very effective means of escaping
predators.
•A second defense mechanism is camouflage or protective coloration.
One form, cryptic coloration, allows the animal to blend in with its
environment to avoid being detected.
•It is important to note that predators also use cryptic coloration to
avoid detection by unsuspecting prey.
.
•Grazing animals often feed in herds. When a predator attacks,
the animals scatter and run in different directions which confuses
the predator and allows the animals to escape.
•Some animals never venture too far from their home in
underground dens or thick vegetation and can quickly hide
when danger approaches.
.
•Many animals have keen senses of sight, smell, and
hearing so that they can detect danger and escape.
.
•Some animals are active only at night when it is harder
for predators to find them.
.
•Trickery can also be used as a formidable defense. False
features that appear to be enormous eyes or appendages
can serve to discourage potential predators.
•Mimicking an animal that is dangerous to a predator is
another effective means of escape.
Responses of thePrey
FLEE!!
!!
Responses of thePre y
walking stick
(cryptic coloration
Invisibility Cloak
(cryptic
coloration/
camouflage)
four-eyed butterfly fish
When predators attack the
wrong end, the butterfly
fish can swim away in the
other direction
•It is important to remember that crypsis is not
just a morphological adaptation, but that
behavior plays a very important part as well.
•Crypsis works only if the animal is resting
on the appropriate background and usually
only when the animal isn't moving.
•Cryptic coloration is especially common in
small animals such as insects, lizards,
snakes, and frogs.
Flash coloration
•Individuals are cryptic at first. When prodded, they may
fly or jump about, suddenly flashing brightly-coloured
appendages or underwings normally hidden at rest.
•Predators encountering these prey are startled and jump
back, which may give the prey a chance to escape.
Red Leafwing - Siderone
marthesia
Siderone marthesia (Nymphalidae) is a rare species of butterfly,
distinctive by its bright blood red marks on the upperside.
A perfect example of “flash” coloration, which startles a
predator or confuses it when it suddenly “disappears” to look
like a brown leaf.
Predators are distracted and search for blue or red objects,
which of course have disappeared when the animal settles
again.
Responses of thePrey
3) Eat me and die (poisons and aposematic
coloration):
Aposematism "advertising"
/warning signal .
•conspicuous colours,
•sounds,
•odours .
Granulated poison arrow frog
The bright colours of the granular poison frog serve as a warning to
predators of its noxious taste. it uses poison only for self-defense from
predators
•In Aposematism, the warning signal identifies an animal as
unpalatable, or distasteful to the inquisitive predator.
•Besides being unpalatable, certain animals may also
internally produce a toxin, which will disrupt digestion and
harm predators or make them unpalatable.
•Common colors associated with aposematic coloration
include: black, yellow, blue, red and orange.
•Black and dark colors result in faster predator learning
and ultimately aversion.
Monarch Butterflies
•Showsbrightprotectivecolorationtodiscouragepredators
•A"oneeventlearningexperience" for thebird involved.Thebirdwill
neverpreyonamonarchbutterflyagain.
• This is the larva of
the monarch
butterfly; an
example of
aposematic
coloration.
• There is no question
of camouflage here.
Rather this creature
is advertising its
presence.
• The milkweed leaves on which it is feeding contain cardiac
glycosides that are toxic to vertebrates because they block the
activity of the Na+/K+ ATPase that is essential for many cell
functions.
• The larva stores these within its body and thus becomes
unpalatable to vertebrate predators.
• The chemicals remain in the body even after metamorphosis, so
that adults are unpalatable as well.
Responses of thePrey
4) “Shields up”:
(armor):
Responses of the Prey :Mimicry: Sheep in
wolves' clothing
Mimicry: mimic, model and operator
•Location specific
•Not camouflage
Batesian mimicry- looks like a toxic model- but is nontoxic
Mullerian mimicry- looks like a toxic model- AND is
toxic
The hooded malpolon
•The hooded malpolon, or
false cobra
• only mildly venomous,
but it mimics the hood
and defensive displays of
the extremely venomous
and dangerous cobras so
that predators avoid it
If red touches yellow, you're a dead fellow; if red touches
black, you're allright..
The non-venomous scarlet kingsnake (a)
the highly venomous eastern coral snake (b)
Mullerian mimicry
•occurs when two (or more) distasteful or
poisonous organisms resemble each other.
Both species benefit because a predator
who learns to avoid one species will most
likely avoid the other, too.
VICEROY BUTTERFLY NOT A MIMIC OF MONARCH
It is important that the Batesian mimic be less common than the
toxic model species.
Responses of thePrey
6) Strength in
Numbers:
Edmund Brodie Jr. (a.k.a. "Butch")
Pretty but deadly
Rough-skinned newts usually blend into their surroundings, but
when disturbed they curl up to reveal a bright orange underside.
APOSEMATISM????????
?
•Butch injected potential predators,
like birds andreptiles, with different
concentrations of a newt skin
solution or offered them newts to
eat.
•When exposed to the toxin, these
predators became wobbly or weak in
the knees.
•They sometimes vomited, stopped
moving, or had a fall in blood
pressure.
•All in all, the predators became
very sick when exposed to newts.
•The evidence supported the
hypothesis that newts had evolved a
defensive poison.
chemists identified the newts' poison as a neurotoxin called
tetrodotoxin, or "TTX."
One rough-skinned newt could have enough TTX to kill 200
great blue herons (left) or 2000 belted kingfishers (right).
Why would a newt
evolve to be so toxic?
Isn't all that TTX,quite
literally, overkill?
•Natural selection should cause newts to evolve TTX
levels just high enough to protect them from predators.
•Newts use a lot of energy making ttx — energy that
they could otherwise spend on finding food, growing
faster, or reproducing.
If toxicity level is indeed inherited (as it seems to be), high toxicity
newts will produce highly toxic offspring and low toxicity newts
will produce offspring with low toxicity.
Because they had more offspring, newts with just the right
amount of toxin are more frequent in the next generation.
Evolutionary theory predicts that natural selection will weed
out newts with too little or excess TTX so that newt
populations should be equipped with just enough TTX to kill
their predators and no more.
But if that's true, then how did newts evolve to be so
poisonous?
The mystery of too much TTX
A garter snake eating a newt
The two species may have been
evolving in response to each other.
Coevolution
•When two or more organisms each evolve in response to each other, we call
it coevolution.
•Butch hypothesized that ttx-laden newts were favored because they could
avoid getting eaten by garter snakes, and that garter snakes with ttx-resistance
were favored because they could survive encounters with deadly newts — in
other words, that newt toxicity and snake resistance had coevolved.
Is it coevolution?
Tradeoffs between the costs and benefits of toxicity and resistance
Too much resistance results in a much slower snake that is more
likely to be eaten by snake predators, but too little resistance would
mean death for any snake that tried to eat anewt.
If snakes and newts are coevolving, their
traits should match up — that is, because
TTX production is costly for newts and TTX
resistance is costly for snakes, newts should
be just toxic enough to avoid predation and
snakes should be just resistant enough to eat
a newt.
Trait matching and a tie game
•Where low toxicity newts occur,
the snakes in the area have low
resistance.
•Newts of intermediate toxicity
occur with snakes of
intermediate resistance, and in
some populations,Brodies
discovered extremely toxic newts
that were being eaten by snakes
with extreme resistance

About 50 years ago, an evolutionary biologist named
J.B.S. Haldane suggested that the interaction between
parasite and host (or predator and prey) should
resemble an evolutionary arms race:

First a parasite (or predator) evolves a trait that allows
it to attack its host (or prey).

Next, natural selection favors host individuals that are
able to defend themselves against the new trait.

As the frequency of resistant host individuals increases,
there is natural selection for parasites with novel traits to
subvert the host defenses.

This process continues as long as both species survive.
EXAMPLE OF PARASITE-HOST COEVOLUTION
Monarch butterfly larvae and milkweed
Cardiac glycosides and milkweed
immunity
Egg mimicry in Passiflora: Female Heliconius and Passiflora
•Heliconius females avoid laying eggs on plants already occupied by
eggs, because larvae of heliconius are highly cannibalistic;
•The plants exploit this habit of heliconius by creating fake yellow
eggs as deciduous buds, stipule tips, or as part of the "extrafloral
nectaries" on youngleaves.
•Clearly, the plant, whose defenses of glycosides, alkaloids, and a
host of other secondary compounds, have been breached by
heliconius, has counter evolved new defenses against this genus
Red Queen hypothesis
‘In our country,’ said Alice, still panting a little, ‘you’d generally get to
somewhere else – if you ran very fast for a long time, as we’ve been doing.’
‘A slow sort of country!’ said the Queen. ‘Now, here, you see, it takes all the
running you can do, to keep in the same place. If you want to get somewhere
else, you must run at least twice as fast as that!’
Lewis Carroll’s Through the Looking Glass
The Red Queen principle suggests that competing species may have to
allocate more and more resources into fighting one another for a modest or
negligible increase in benefit.
Altruism and Co-operation
Altruism.
z Altruism refers to an individual acting in a way that will
decrease its own survival chances, but improve the survival
chances of another individual.
z The Darwinian perspective emphasising ‘survival of the
fittest’ gave the impression that selfishness was the norm.
z Pioneering work involving the study of animals living in
social groups in fact revealed that co-operation and
altruism are just as ‘natural’ as selfishness.
z If co-operation and altruism have evolved, then they must
have some adaptive benefits, researchers have analysed
the conditions under which adaptations for engaging in
such behaviour can be expected to evolve.
Examples of Animal Altruism.
z Ground squirrels will warn others
of the presence of a predator,
even though making such a call
may draw the attention of the
predator to itself (Sherman,
1977).
z In many species of social insects,
workers
forgo
reproduction
entirely (they are sterile) in order
to help raise their sisters (Wilson,
1971).
Ground squirrels
Examples of Animal Altruism.
Elephants That Care and Grieve
• Elephants have the longest gestation time of any
land animal -22 months - meaning that the bond
between mother and baby is particularly strong.
• Experienced mothers in a herd often show care
and concern for new mothers who need extra
help with their babies.
• The veterans will take turns looking after the
new baby, guiding it with their sensitive trunks,
giving time for the new mother to gain energy so
she has enough quality milk for her offspring.
• There are also documented examples of adult
elephants helping to rescue a baby elephant
when it became stuck in deep mud at a watering
hole in Africa.
• Behaviour like this helps ensure the group
survives and bonds the herd together.
The Praying Mantis is a predator,
carnivorous and cannibalistic insect.
Very often, the female eats the male
head during or after mating, probably,
as a reproductive strategy to enhance
fertilization while obtaining food.
Honey bees use the sting
against enemies when they
perceive the hive to be
threatened. When this happens,
the honey bee dies because the
entire stinging apparatus is
pulled from the bee’s abdomen.
This is an example of altruistic
behavior in social colonies.
Vervet monkeys (mainly females)
generally have an altruistic
behavior when they see a predator.
They emit a warning call to alert
the rest of the group of an imminent
danger. In doing so, they attract all
the attention to themselves risking
their lives and chances of survival.
Adélie penguins have shown selfish
actions in their natural habitat.
Sometimes, one of the individuals is
pushed off into the cold waters of
Antarctic while the others observe if
the chosen one is safe or not. If there
is no danger, the other penguins
jump off the cliff into the water.
Dedication of The Deep Sea Octopus
• The mother, laying between 50,000 and
200,000 eggs, shows real dedication
during the 8 weeks of her life when she
protects her potential babies.
• Once the eggs have been laid in a safe
place she will push currents of water over
the eggs so they get enough oxygen,
keeping them alive.
• So busy is the female octopus her food
intake lowers and often mothers just fade
away to nothing in an effort to keep the
babies alive.
• Once they have hatched out she will die.
Sand Grouse
• The sand grouse of southern Africa
displays amazingly caring behaviourby
travelling long distances to fetch much
needed water for its young.
• The male often flies miles to a fresh
water lake where it will wade in and
immerse itself in the life saving waters.
•
Special feathers help keep the water
close to the bird's breast as it flies back to
the nest.
• When the young have had their fill,
snuggling up close, the adult bird then
dries off again before starting another
water journey.
Theories of Altruism.
z
Kin Selection
Hamilton, 1964).
(Proposed
by
z By helping relatives to reproduce
(even at the cost to your own
reproductive success) then your
shared
genes
can
spread.
Assisting a close relative thereby
increases one’s ‘InclusiveFitness’.
Kin Selection in Action.
z Ground squirrels will warn others of the presence of a
predator, even though making such a call may draw the
attention of the predator to itself (Sherman,1977).
z Ground squirrels do not give an alarm call every time a
predator approaches. They only do so when there is a large
proportion of their relatives within earshot .
z Vampire bats will regurgitate and feed blood that they have
collected from their prey to a hungry conspecific
(Wilkinson, 1990).
z Vampire bats are much more likely to share their food with
relatives than with non-relatives (Wilkinson, 1990).
Kin Selection and Inclusive
Fitness
z Imagine a gene which causes its bearer to behave
altruistically towards other organisms, e.g. by sharing
food with them.
z Organisms without the gene are selfish—they keep all
their food for themselves, and sometimes get handouts
from the altruists.
z Clearly the altruists will be at a fitness disadvantage, so
we should expect the altruistic gene to be eliminated
from the population.
z However, suppose that altruists are discriminating in who they share food
with. They do not share with just anybody, but only with their relatives.
This immediately changes things.
z So when an organism carrying the altruistic gene shares his food, there is a
certain probability that the recipients of the food will also carry copies of
that gene.
z This means that the altruistic gene can in principle spread by natural
selection.
Kin Recognition.
z It is important to be able to recognise kin, as the costs
involved in mistaking another individuals offspring for
one’s own are high, and the benefits few.
z Offspring recognition should evolve more often in colonial
species, as there is a high risk of misdirecting parental care.
z Examples.
z Bank swallows (colonial) do not accept strange chicks
whereas rough-winged swallows (solitary) do.