Transcript Co-evolution involves the joint evolution of two or more species as a

Chapter 10 Co-Evolution
Co-evolution involves the joint evolution of two
or more species as a consequence of their
ecological interaction.
Each species is partially dependent upon or
threatened by the other, thereby producing
reciprocal selective pressures.
Symbiosis means living together, an ecological
coupling of two or more species in a coevolutionary relationship.
If both partners benefit, the relationship is
mutualism.
If one benefits the other is at least not harmed, is
commensalism.
When one species loses and the other gains;
predation (predator and prey), parasitism (parasite
and host), herbivory (herbivore and plant).
Spines; cactus, with projecting thorns
Chemical warfare
Some herbivores have tough tongues and steely
mouths
Small insect herbivores evade the spines by
simply navigating around them to
Plants under such attack often produce chemicals
that are unpleasant in taste or even toxic in effect;
secondary chemical compounds.
Their central function is to provide the plant with
chemical weapons to frustrate natural enemies.
Nicotine in tobacco plants; against herbivorous
insects
disrupting their metabolism and probably
carrying a foul taste
Seeds of some morning glories include dlysergic acid, close chemical cousin to LSD,
with hallucinogenic properties
Members of the mustard family include
mustard, radish, horseradish, cabbage,
and watercress, all of which contain
mustard oil.
Some plants, such as milkweeds and
dogbane, produce milky sap containing
cardiac glycosides, named for their
potentially lethal effects on the heart of
vertebrates but equally toxic to many
insects.
殺不完的昆蟲
Plants have been in chemical conflict with
herbivores, insects in particular, for millions of
years.
When humans, late participants in this chemical
warfare against insects, are quickly defeated by
insects that evolve resistances to humans –
engineered chemical pesticide. Insects have
been waging this old battle of chemical warfare
against plants for millions of years.
身經百戰的昆蟲
Mutualisms
What they do not digest, they excrete as a droplet
of water containing undigested sugars, known as
“honeydew.”
Some species of ants collect this excreted
honeydew, using its sugars as a resource.
Directly solicit the aphids to release the drop of
honeydew. And in some interactions, the ants may
actively protect the aphids from their predators,
Aphids benefit from the protection afforded by
the attending ants.
Ants and Aphids-Mutualism
• These ants tend their “herd” of aphids,
which in turn secrete fluids rich in sugars
drunk up by the ants.
Ants and Fungus
Attini ants, denizens of the New World tropics,
culture and then eat the fungus (genus
Leucocoprini) in safe, underground “gardens”
within their burrows. The fungus is grown on a
mixture of excrement fertilizer, from the ants,
and fresh plant material gathered aboveground
by the ants.
Leaf-cutter
ants—mutualism
The ants chew up the
leaf pieces into even
smaller pieces (1-2 mm),
munching them into a
pulp, and insert the pulp
into the garden plots
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Ants then pluck tufts of the fungus
Overall, both ants and fungus benefit.
For the ants, it is a sustainable crop. For the
fungus, it is care and nurturing.
Ants chew up the antifungal defenses of the
plant (such as its waxy coating), and the fungus
degrades the anti-ant defenses (insecticides) of
the plant, such as its secondary chemical
compounds
This chummy world of ant farmer and fungus
garden invites the invasion of “weeds.” The
weed is a virulent parasitic fungus (genus
Escovopsis).
In response, ants carry on their bodies a
bacterium (genus Streptomyces) that produces
antibiotics
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Acacia tree (Acacia cornigera)
Ants (Pseudomyrmex ferruginea). Along its
branches, the acacia provides the ants with
small pools of nectar drunk up by the ants and
Beltian bodies picked and fed to ant larvae;
further, the inflated, hollow thorns of the acacia
provide a home in which the ants live.
The ants protect the acacia from browsing
mammals; The ants also attack herbivorous
insects that alight on the acacia. Further, the
foraging ants eliminate adjacent, competing
plant species by eating their leaves.
Ants and Acacias-Mutualism
The ecologist, Daniel Janzen, removed the ants
from their associated acacia trees by clipping
off branches that held the colony of ants or by
temporarily eliminating the ants with insecticide
spray.
Quickly became vulnerable to unchallenged
attacks by phytophagous insects
the acacias were overgrown by competing
shrubs and trees . Essentially, the ants provide
a standing army for the acacias,
How it evolved
Perhaps the first step would be the evolution of
thorns by the acacia.
Next, the facultative or casual use of these
thorns as nest sites by tic association.
Defoliates competitor plants
The by-product of this attack would be to fend
off acacia enemies
produced supplementary food
Honeybees and Flowers
Gymnosperms produce pollen, packets of
sperm, carried usually by the wind to female
ovules where fertilization occurs. Instead of
wind, flowering plants often employ animal
vectors, directed transfer agents, to carry pollen
more or less directly from male to female
flowers.
Butterflies; hummingbirds; honeybees
Honeybees and Flowers
The colors and smells both catch the attention
of honey bees and, signal the availability of food
and ripe pollen.
Honeybees have special bristles on their legs”pollen baskets”-which
The honeybee gains a resource from the flower;
the flower gains a traveling agent to deliver its
pollen.
Honeybees and Flowers
Hummingbirds and flowers
Hummingbirds feed on insects, but they are
outfitted with specialized long beaks and
tongues to drink up nectar
they are specialized to tap resources supplied
by flowers but they also act as pollinators as
they move from flower to flower.
Hummingbirds may visit one site only during a
short block of time.
Hummingbird feeding on a flower
Angiosperms, which cater to hummingbirds as
their pollinator, bloom during the spring as
hummingbirds pass through on their way to
northern breeding territories.
Many flowers; tubular and narrow at their base,
Tends to prevent roving insects from pirating
nectar saves it for hummingbirds with long
beaks and tongues
Practical and Functional
Biologists placed around the grounds small,
clear dishes of sugar water on colored
backgrounds; attracts butterfly
clearly preferred two particular colors,
yellow and purple. These turned out to be
the flower colors they preferentially visited
as well.
Our eyes do not see in the ultraviolet range
of light, but the eyes of some insects do
• Note the
distinguishing
nectar guides, the
spots near the
center of the flower.
Mutualism—fish
• The small Spanish hogfish dashes into the
mouth of a willing barracuda where it
feeds on debris and parasites. The hogfish
gains a meal and the barracuda gains a
cleaning.
Mutualism—birds and crocodiles
• This African crocodile relaxes and holds its
mouth open. This signals Egyptian Plovers
to enter and safely feed on fouling
parasites and debris. The crocodiles gain
a cleaning, and the plovers a meal.
Mutualism—oxpecker
• This red-billed oxpecker forages for
parasites on the backs of African
ungulates. Here the oxpecker is working
around the neck of domestic cattle.
Parasites tend to collect along the back of
the neck where scratching cannot dislodge
them. The oxpecker gains a meal, and its
customers get rid of parasites.
Commensalism
“looking-glass” orchids, are visited not by bees,
but by wasps.
At first, that puzzled biologists. Wasps are
usually scavengers and predators.
For wasps, pollen is not a resource to be
harvested.
Looking-glass orchids do not even produce
nectar, yet wasps visit, and hence the puzzle.
Not to find food but to satisfy the prurient
interests of male wasps- for sex.
It is not known for how long or for how many
times a male wasp continues his unrequited
quest, but looking-glass orchids are a very
successful group of plants.
The skunk cabbage is named for the unpleasant
odor, human senses.
Humans often describe this plant as smelling like
rotting meat or dung. But to the sensitivities of
many insects, these welcome odors
signal useful resources. Flies and
scavenging beetles seek out
decaying meat or dung, respectively,
where they lay their eggs.
When the flower ripens, it warms, up to 40℃,
volatilizing the chemicals within that drift out into
the air to attract the insects.
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Overview: commensalism.
Certainly, the looking-glass orchid benefits from
the amorous travels of the male wasp, but the
wasp receives no biological return.
Similarly, the skunk cabbage benefits from
insect pollinators, but the insects fond no
beneficial resource.
Some biologists argue that these are not
examples of commensalism (benefit/no harm),
but of behavioral parasitism (benefit/harm)-only
the plants gain in the interaction, the insects lose.
Initially, ancestors to skunk cabbages may have
depended on all available insect pollinators. But
skunk cabbages are physiologically adapted for
life in wet and soggy places, dim light, and
shade.
The skunk cabbage only needs to a built- in
attraction to some flies and beetles, in which it
is a sensory delight already in place as part of
their own reproductive quest.
Camouflage
Sometimes it pays to hide. Organisms that conceal
themselves from enemies may do so with
camouflage or cryptic coloration and shape.
Rounded “stone plants” live in arid and
open habitat, they are the shape of
inedible stones, and silver skinned
Many animals, like plants, looks like an
uninteresting dry stem;
only falls to the ground and continues
the deception, remaining motionless
Camouflage—inedible
The resemblance of these insects to inedible plant parts affords them
some protection from prowling insect-eating predators, such as birds.
Camouflage—coloration and shape
• This dwarf seahorse (center) is camouflaged within the
branches of this colonial sea fan. Reef, Solomon Islands.
Camouflage—arctic hare
• This hare depends upon its white color to blend into the snowy
background. When discovered, it turns to speed to make an
escape from predators.
Harbor seal pup
• The white coat of the harbor seal pup affords some camouflage
with the ice and snow upon which it spends much of its early
life when it is especially vulnerable to predators.
Camouflage—predator
• This stonefish is encrusted with various creatures of the
coral reef, camouflaging it to unsuspecting prey that
cruise by.
Sometimes it pays to advertise. Coloration that
publicizes an organism’s presence is warning
coloration or aposematic coloration.
Arrow frogs of tropical South America
toxic skin
the toxins must be ingested or enter the
bloodstream, to be dangerous
The cooking denatures the frog toxins.
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Sometimes animals do both-hide and advertise.
The screech owl, tucks itself up against the tree,
closes its headlight –like eyes;
owl puffs up, spreads its wings, displays its bright
eyes, and tries to look formidable.
Venomous rattlesnakes
remain silent, not move or rattle its tail.
It turns into a flurry of display; warning behavior.
Sometimes it pays to startle.
Eye spots occur in moths, on caterpillars, and
even on the rumps of frogs.
Namely, to startle the predator long enough to
make an escape
Startle Response, Eyespots on Butterfly
MIMICRY
Sometimes it pays to impersonate. The superficial
resemblance between two or more organisms that
results from a co-evolutionary relationship is
termed mimicry.
The term mimicry is usually applied in a strict
sense to two general categories of mimicry:
Batesian mimicry and Müllerian mimicry, each
named for the first person to publicly recognize the
type.
Mimicry II
• a) Batesian mimicry between toxic monarch (model) and harmless
viceroy (mimic), left and right, respectively.
• b) An example of Müllerian mimicry, where both ecologically
sympatric pairs are distasteful, and both have warning coloration.
In batesian mimicry, one species is dangerous
or distasteful and can back up its boastful warning
coloration with unpleasant consequences for
woukld-be predators. This species is the model.
The other look-alike species is the mimic. The
mimic is brightly colored and shaped like the
dangerous model,
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The monarch butterfly contains sequestered in its
tissues noxious chemicals (cardiac glycosides). If
eaten by the bird, these chemicals are released,
causing nausea and vomiting.
The unpalatable chemicals are picked up during
their larval stage; Safely sequestered in
concentrated fat bodies
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Raised monarch caterpillars on milkweed plants;
Raised M. caterpillars on plants without toxins
Blue Jay Learning Aversion to Distasteful Monarch
(a) This hand-reared blue jay, having never eaten a monarch, rips off
the wings and gobbles down the body. (b) The toxins quickly make
the blue jay sick, and it spits up the monarch. Thereafter, even if
presented a monarch lacking such toxins, the blue jay refuses it.
Evolution of toxin in the tissues of milkweed
plants. 摩蘿科馬利筋
Monarch evolves a tolerance for the milkweed
toxins
Adult acquires toxins noxious to its predators
Evolution of warning coloration
The closer in appearance of viceroy (mimic) to
monarch (model), the more the viceroy benefits
from predator avoidance.
In batesian mimicry, the mimic benefits but the
model may actually find its survival threatened,
especially if the harmless mimic becomes too
common.
Other cases between the venomous and
dangerous rattlesnake (model) and the
nonvenomous gopher snake, or bull snake (mimic).
Rears back; producing a rattling sound
When the nonvenomous gopher snake is
threatened, it will similarly assume a defensive
posture; no tail rattle, but it can vibrate its tail
against dried leaves
Between a distant relative of cobras-the highly
venomous coral snakes (model);
Some brightly colored species of the
nonvenomous kingsnakes (mimic). Both are
brightly colored with rings of black, yellow, and red
around their bodies.
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Red and yellow is deadly coral snake;
Red and black is a harmless kingsnake.
Although predaceous birds see in color, most
predatory mammals do not. Foxes, wolves,
badgers, raccoons, weasels, and coyotes see in
shades of gray.
In motion, these bands would pass the eyes of a
predator at a high “flicker frequency” and be seen,
not as bands, but as a blended gray.
From the standpoint of the predator, the banded
snake it sought to grab would disappear in front of
it. Or the predator would experience momentary
confusion, gibing the snake a chance to escape.
Flicker Frequency
A newborn watersnake shown crawling (a, c) and motionless (b, d).
In motion, the snake’s banding pattern looks evenly gray, as it
would when exceeding the flicker frequency of a predator.
No opportunity for the predator to carry away the
lesson learned.
Hand-reared motmots avoid coral
snakes upon their first encounter.
They even avoid thin wood dowels,
snake size, painted with adjacent,
repeating yellow and red bands.
Learning is not necessary, as motmot
avoidance genetically; innate
behavior the birds possess from birth.
In Müllerian mimicry, both species come to
superficially resemble each other, but both species
are unpalatable or dangerous to their predators.
In a sense, each unpalatable species is the model
for the other.
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Mimicry in
insect
Müllerian mimicry—Many bees, yellow jackets, and wasps have a
common, bright yellow/black warning pattern, which they can all
back up with an unpleasant sting. Batesian mimicry—Harmless
syrphid flies evolved a similar color pattern, taking advantage of
the avoidance of the yellow/black pattern.
In aggressive mimicry, the prey do not mimic
something predators avoid or overlook; instead,
the predator does the mimicking. It is a wolf in
sheep’s clothing.
Some predaceous fireflies flash at frequencies
that mimic the flashing of females of other species.
The angler fish is
dressed in leafy cover
so it looks like a harmless
algae covered rock.
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Cleaner fish feed on the ectoparasites and bits of
dead skin on other fish, removing them
The customer relaxes, it opens its operculum, the
protective bony cover over the fleshy gills, and this
allows the cleaner fish to dart in and about, picking
off parasites
Job done, the cleaner fish dashes off to other
customers, and the spiffed–up fish returns to its
predaceous ways in the reef.
Mutualism—fish
• The small Spanish hogfish dashes into the
mouth of a willing barracuda where it feeds on
debris and parasites. The hogfish gains a meal
and the barracuda gains a cleaning.
team
of divers
onestriped
cleanerfish
fishworking
counted
• AThe
cleaner
fishfollowing
is the small,
more
than
300
fish customers
visiting
in fish,
a 6-hour
around
the
relaxed
mouth of the
larger
period.
gathering up bits of debris.
These aggressive mimic fishes, about the
same size and color as the cleaner fish,
belong to a different family of fishes
altogether.
These dash in to take bites out of the fleshy
gills and chunks of living flesh from fins and
tail. This aggressive mimic is a predator,
masquerading in “sheep’s clothing.”
Dodo bird (extinct)
Long-term options may be lost to short-term
benefits of a symbiotic relationship. On the island
of Mauritius, off the coast of Africa,
Flightless dodo bird until the seventeenth century,
when the species became extinct.
The last dodo was killed in 1681
the gizzard, works small pieces of swallowed
gravel against ingested seeds to grind them down
Biologists took come of the seeds and fed them
to turkeys,
Some of the seeds safely passed through the
turkeys, were collected, planted, and germinated.
Pollinators and their flowers are also intertwined
ecologically.
But if the plant changes flowering time, it risks
losing its pollinator; if the hummingbird changes
course or migration time, it may meet no opened
flowers at crucial legs along its journey. Both are
linked in their evolutionary destinies.
Aphids; ants
Fish had parasites before cleaner