Download How did this mutualism evolve?

Mutualism
Mutualism
Mutualism: Inter-specific relationship from which both species benefit
Symbiosis: Intimate (generally obligate) inter-specific relationships from which
both partners benefit
Mutualism
How did this mutualism evolve? What are the origins?
1. Antagonistic origin in a predator/prey relationship
Pollination by animals (ie birds, bees, moths, butterflies, beetles, ants, mammals)
Pollinators receive food rewards (nectar and pollen), plants have pollen moved to
other flowers
How did this mutualism evolve? What are the origins?
1. Antagonistic origin in a predator/prey relationship
Early plants were probably
wind pollinated and insects
were predators feeding on
spores, pollen or ovules
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How did this mutualism evolve? What are the origins?
1. Antagonistic origin in a predator/prey relationship
Early plants were probably wind pollinated
and insects were predators feeding on
spores, pollen or ovules
By chance, some floral visitors were
less damaging and perhaps even
beneficial in moving pollen between
plants, thus selecting for traits in
plants that would minimize damage
and cost and maximize pollen transfer
How did this mutualism evolve? What are the origins?
2. Evolution of plant traits that minimize negative impact of insects
a) protect ovules and pollen
How did this mutualism evolve? What are the origins?
2. Evolution of plant traits that minimize negative impact of insects
a) protect ovules and pollen
Closed carpel to protect ovules
Defend pollen
with chemical or
physical defenses
How did this mutualism evolve? What are the origins?
2. Evolution of plant traits that minimize negative impact of insects
b) minimize cost of rewards
Bees are sophisticated pollen
predators
Pollen is an
expensive reward,
but nectar is cheaper
Bilateral symmetry in flowers
minimizes pollen predation by bees
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How did this mutualism evolve? What are the origins?
3. Evolution of traits that attract beneficial insect pollinators
How did this mutualism evolve? What are the origins?
4. Evolution of traits that increase specialization
By restricting access to only the most
efficient pollinators, pollen will more
likely be transferred to a conspecific
(same species) rather than wasting
pollen on the wrong species
Visual attraction with UV patterns
Long corollas require
long tongues
Visual attraction
Olfactory attraction
(nocturnal pollinators)
How did this mutualism evolve? What are the origins?
4. Evolution of traits that increase specialization
Evolution of syndromes for a subset of pollinators, e.g. humming bird
flowers are red, tubular, easy access for hovering birds, high amounts
of nectar, low concentrations
How did this mutualism evolve? What are the origins?
4. Evolution of traits that increase specialization
Evolution of syndromes for a subset of pollinators, e.g. bat-pollinated
flowers are white, open for easy access, high amounts of nectar at night,
lots of pollen to compensate for high nectar costs
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How did this mutualism evolve? What are the origins?
4. Evolution of traits that increase specialization
How did this mutualism evolve? What are the origins?
4. Evolution of traits that increase specialization
Fly pollinated
flowers smell like
rotten flesh, are
often purple or
brown, can heat
up and give no
reward (faking out
the carrion flies)
Orchids have very specialized coevolved
relationships with male orchid bees which visit
flowers to collect chemicals to incorporate into
their sexual pheromones (perfumes)
How did this mutualism evolve? What are the origins?
4. Evolution of traits that increase specialization
How did this mutualism evolve? What are the origins?
5. Animals will be under selection to maximize rewards and avoid defenses
This orchid smells
and looks like a
female fly, so
male flies visit the
flower, try to
“copulate” with the
flower, and in the
process transfer
pollen (another
example of faking
out the flies
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Scarlet gilia : an example of selection between pollinator and plant
Common in mountain meadows throughout the west.
Polymorphism for flower color (white and red)
Seasonal shift selection for flower color: ref favored early and white favored late
Percentage seed set
Percentage of total pollinators
Scarlet gilia : an example of selection between pollinator and plant
white
red
Percentage of total plants
July
Red preferred by humming birds, white by hawkmoths
July
August
August
Fruit dispersal by wind, water, gravity and animals
1. Origin in seed predation
Scatter hoarding by seed
predators (storing seeds for
later consumption), but some
seeds escape and germinate
Jaguars
Jaguars
Mammals
Mammals
Large <==> Small
Seeds
Seeds
Large <==> Small
Seeds
Seeds
Seed predators/dispersers influence seed
establishment and plant composition
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Fruit dispersal by animals
2. Seeds are expensive and valuable, so plants evolve mechanisms to
defend the seed (usually with toxins).
3. Plants evolve a cheaper reward to attract dispersers (fleshy fruits).
4. And attractive displays (color).
Acacia seeds with fleshy aril for dispersay by birds and ants
Fruit dispersal by animals
Advantages to the animals - food supply
Resplendant Quetzal
and wild Avocado
(Lauraceae)
Fruit dispersal by animals
2. Seeds are expensive and valuable, so plants evolve mechanisms to
defend the seed (usually with toxins).
3. Plants evolve a cheaper reward to attract dispersers.
4. And attractive displays (color).
Evolution of edible fruit parts and inedible seeds (offspring) minimizes seed
destruction and maximizes dispersal
Fruit dispersal by animals
Advantages to the animals - food supply
Some plants have
adaptations for specific
dispersers
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Fruit dispersal by animals
Advantages to the plants
1. Reduces competition between seedlings and parent plant
Fruit dispersal by animals
Advantages to the plants
2. Gets seeds deposited with package of nutrients
Fruit dispersal by animals
Advantages to the plants
3. Targeted dispersal to specific specialized sites
Fruit dispersal by animals
Advantages to the plants
4. Avoid specialized herbivores and
seed predators that are
concentrated on the parent tree
mistletoe plant
mistletoe seeds stuck to bark
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Fruit dispersal by animals
Advantages to the plants: an example from wild nutmeg (Virola)
Number of
seeds
dispersed
Greatest
success of
seedlings
Number of
seedlings
surviving
Distance from parent
from Janzen and Connell
If all seeds landed under the parent plant, there would be no successful
recruitment of seedlings due to specialized herbivores and seed predators
This will prohibit the establishment of single species stands and increase
forest diversity
All seeds
killed by
weevils
Increased seed
survival farther
from parent
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