Download Topic 13

Bio 1309 Intimate Partnerships
How Species Adapt to Each Other
Slide 1
Adaptive Evolution
• Adaptive evolution =
natural selection acts
on genetic variation in a
population
• Organisms with best
adaptations for that
environment have more
offspring than other
members of their
species
Slide 2
Species Effects
• Natural selection =
result of environment
– (not just physical, also
biological)
• Other species around us
have effects in addition
to environmental
physical components
Slide 3
Species affect evolution
• How different species
affect each other’s
evolution
Slide 4
Orchid Example
Fool Me Once…
• Orchids are mean
• Most plants offer a
reward to their
pollinator(s)
–
–
–
–
Nectar
Pollen
Oil bodies
Sex
Slide 5
Orchid Example
Sex mimic…
• Sex you say?!?
• Some species of orchids
trick their pollinators by
mimicking females of
the species
Slide 6
Orchid Example
The wasp…
• Lissopimpla excelsa
– Orchid dupe wasp
• Native to Australia
– Pollinates all five
Australian members of
the orchid genus
Cryptostylis
Slide 7
Orchid Example
Fools Male Wasp…
• Shaped like a female
wasp
• Looks like a female
wasp
• Smells like a female
wasp
• Emits pheromones that
mimic female wasp
pheromones
Slide 8
Orchid Example
Male pollenates…
• Male wasp fooled!
(thinks flower is female
wasp and attempts to
mate - in process, picks
up pollen
• When male wasp tries
to mate with another
flower, pollen transfers
Slide 9
Orchid Example
pseudocopulation…
• Pseudocopulation:
Male wasp extends
genital claspers into the
flower and deposits
sperm on the flower
Slide 10
Species Relationships
Predators, Parasites, Deceivers & Their Victims
• The relationships
between different
species are diverse and
varied:
– Shrimp that clean fish
– Cuckoos that trick other
birds into raising their
young
Slide 11
Positive-Negative
Predators, Parasites, Deceivers & Their Victims
• One way to organize
this diversity of
relationship: measure
the effect one species
has on another species
fitness
– Effect can be:
• Positive
• Neutral
• Negative
Slide 12
Positive-Negative
Predators & Prey
• Predators and prey have
a positive-negative
relationship
– Predators depend on
their prey as a food
source
– Predators can reduce
their prey’s fitness to
zero
Slide 13
Positive-Negative
Parasites
• Parasites can also have
a positive-negative
relationship with their
hosts
– Parasites may kill or
weaken their hosts as
they multiply
Slide 14
Positive-Negative
Fitness is about reproductive success!
• Not necessary for
organisms to die to
have its fitness lowered
by another species
– Fitness is not just about
survival
• Ultimately, fitness is
about reproductive
success
Slide 15
Positive-Negative
Parasitic barnacle
• Parasitic barnacle,
Sacculina
– Host is a crab
• Barnacle burrows into
the crab’s body and
grows tendrils
throughout the crab’s
tissues
– Crab shows no signs that
it’s being “invaded”
Slide 16
Positive-Negative
Parasitic barnacle (cont…)
• Crab carries on
normally- searching for
food and eating
• The barnacle destroys
the crab’s sexual organs
so it can no longer
reproduce
Slide 17
Positive-Negative
Parasitic barnacle (cont…)
• The Barnacle benefits
because host no longer
expends energy looking
for a mate or having
babies… just looks for
food and eats!
Slide 18
Positive-Negative
Parasitic barnacle (cont…)
• The crab, is at an
evolutionary dead end
because its
reproductive fitness has
been reduced to zero
Slide 19
Positive-Negative
Wasp – Orchid revisited
• In the case of the wasps
and orchids, evidence
that fitness of the wasp
may be lowered
– Wasp uses sperm on
orchids = Less sperm to
fertilize female wasps
Slide 20
Positive-Negative
Wasp – Orchid revisited (cont…)
• Relationship benefits orchid so
Orchid’s reproductive fitness is
increasing
• Possible downside: Depends on
wasps! (Can only be pollinated
by the wasps)
Slide 21
Positive-Negative
Wasp – Orchid revisited (cont…)
• Interactions between
the wasps and the
orchids change each
species fitness =
natural selection is
driven in both species
Slide 22
Positive-Negative
Wasp – Orchid revisited (cont…)
• Mutations that enable
male wasps to
distinguish between
orchids and real female
wasps should be
favored by natural
selection
Slide 23
Positive-Negative
Wasp – Orchid revisited (cont…)
• As wasps improve their
sense of smell, natural
selection will favor
orchids that match the
smell of female wasp
pheromones more
closely
Slide 24
Positive-Neutral
Commensal relationships
• Some species depend
on other species for
their survival
• Have no negative or
positive effect on the
fitness of their partners
– Positive-neutral or
commensal relationship
Slide 25
Positive-Neutral
Commensals
• Remoras hitch a ride by
clamping onto sharks
and other fish
• When the host fish
finds prey, the remora
lets go
• After the host finishes
eating, the remora
cleans up the scraps
Slide 26
Positive-Neutral
Commensal examples
• Commensals are well
adapted to their hosts,
for example:
Pitcher plants live in
nutrient poor habitats but
supplement their diet by
capturing and digesting
insects
Slide 27
Positive-Neutral
Commensal examples (cont…)
• Mosquito larvae feed on
the accumulated dead
bodies of captured insects
inside the pitcher
– These mosquito commensals
have evolved adaptations
that allow them to survive in
this plant stomach
• They are so adapted that they
can live nowhere else
Slide 28
Positive-Neutral
Commensal examples (cont…)
• Birds follow army ant
raids on a forest floor
• As the ant colony
travels on the forest
floor, they stir up
various flying insect
species
Slide 29
Positive-Neutral
Commensals (cont…)
• As the insects flee from
army ants, birds follow
the ants to catch and
eat the insects = the
army ants and birds are
commensalistic because
the birds benefit and
army ants are
unaffected
Slide 30
Positive-Positive
Mutualism
• Mutualism = two
species interact in a way
that benefits both
(relationship is
mutually beneficial)
Slide 31
Positive-Positive
Mutualism examples
• Soil fungi, called
mycorrhizae, form a
mutually beneficial
partnership with plant
roots
– The fungi increase the
surface area of the plant’s
root system
• Plant can absorb more water
and dissolved nutrients
• Fungi absorb some of the food
the plant produces
Slide 32
Positive-Positive
Mutualism examples (cont…)
• Relationship between
the oxpecker (a kind of
bird) and the rhinoceros
or zebra
• Oxpeckers land on
rhinos or zebras and eat
ticks and other
parasites that live on
their skin
Slide 33
Positive-Positive
Mutualism examples
• The oxpeckers get food
and the rhinos/ zebras
get pest control
• Also, when there is
danger, the oxpeckers
fly upward and scream
a warning, alerting
their partner (helping
escape from predators)
Slide 34
Positive-Positive
Mutualism examples (cont…)
• Bacteria and humans:
various species of
bacteria live in the
intestines of humans
(normal flora).
• Bacteria provide
required vitamins
• Help humans digest
some foods
Slide 35
Positive-Positive
Mutualism examples (cont…)
• Bacteria benefit by
getting food and a safe
place to live
• Humans benefit from
bacterial digestion and
the vitamins they
provide along with
water reabsorption.
Slide 36
Positive-Positive
Mutualism examples (cont…)
• Organisms in a mutualistic
relationship evolved
together = coevolution
• Each was part of the other's
environment, so as they
adapted to their
environment, they "made
use of" each other in a way
that benefited both
Slide 37
Coevolution
• Coevolution can often
be diffuse - meaning a
species evolves in
response to its
relationship with a large
number of species –
example: Some plant
species can be
pollinated by various
pollinators
Slide 38
Coevolution –
Example
• Coevolution can be
specific (meaning two
species depend on each
other completely) For
example: Yuccas are
pollinated by specific
species of moths
Slide 39
Coevolution –
Example (cont…)
• Female yucca moths
gather pollen from a
yucca flower
– Carries it to another
flower
– Chews a hole into the
ovary of the yucca
flower
– Lays her eggs in the hole
Slide 40
Coevolution –
Example (cont…)
• Rolls the pollen into a
ball
– Stuffs it into the hole
– Goes on her way
• Yucca flower gets
pollinated
• Baby yucca moth larvae
have a source of food in
the developing seeds
Slide 41
Coevolution –
Locks & Keys example
• Species coevolution can
mold the morphology
of two species so
species match up like
lock and key, for
example: Acacia trees
are protected from
herbivorous insects by
ants
Slide 42
Coevolution –
Locks & Keys example (cont…)
• Ants roam the tree’s
branches and trunk
looking for potential
invaders
• Chase invaders off
• Trees grow hollow
swellings on their
branches and ants live
inside
Slide 43
Coevolution –
Locks & Keys example (cont…)
• In addition, trees
produce a sugary nectar
or oil bodies that feed
the ants
Slide 44
Locks & Keys Coevolution –
example (cont…)
• Leonardoxa spp.
– African rainforest trees
– 3 species
• All guarded by their
own species of ant
– Openings to the
swellings on each
species of tree precisely
match the size of the ant
protecting it
Slide 45
Evolutionary Trees
Mirror
• history of interacting
species seen in their
evolutionary trees
Slide 46
Evolutionary Tree
Mirror example
• Species of gophers carry
particular species of lice
• Compare the
evolutionary trees of
the gophers and lice =
mirror-like symmetry
Slide 47
Evolutionary Tree
Mirror example (cont…)
• Suggests that when a
species of gopher splits
into a new species, the
lice that live on it
diverge into a new
species, too
Slide 48
Mirror Trees
• Mirror trees can also be
used to shed light on
the steps it took for a
particular relationship
to evolve
• Sharpshooters and their
bacteria
– Insects that live on the
fluid in plant xylem
Slide 49
Mirror Trees – more examples
• Sulcia and Baumannia
are 2 bacterial species
that help sharpshooters
digest the xylem fluid
• DNA studies on the
insects and bacteria
show that Sulcia was
living in the sap feeding
ancestor of
sharpshooters 270 mya
Slide 50
Mirror Trees – examples (cont…)
• In more recent
sharpshooter ancestors,
Sulcia is joined by
Baumannia inside the
insects
– Sulcia provides the
insect with amino acids
– Baumannia provides
vitamins and other
nutrients
Slide 51
Mirror Trees – examples (cont…)
Interesting symmetry:
• Baumannia lost
amino acid production
genes except histidine
• Salcia  has retained
amino acid production
genes except histidine
Slide 52
Bacterial coevolution!
• the two bacteria
coevolved with their
host
PLUS
• They coevolved with
each other!
Slide 53