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Defensive Mutualisms – Trade protection for food
Acacia and Acacia ants
Induced and Constitutive Defenses in Acacia.
The species in the right-hand column
have mutualistic relationships with
ant species - the ants nest in the
thorns. Those on the left can attract
ants with extra-floral nectary
secretions, but the ants do not nest.
The Acacia species on the left
increase their nectar secretions after
damage, inducing wandering ants to
come visit and stay a while.
The species on the right have to
support the ant colonies all the time,
and nectar production is uniformly
high and unaffected by damage.
Induced and Constitutive Defenses in Acacia.
The species in the right-hand column
have mutualistic relationships with
ant species - the ants nest in the
thorns. Those on the left can attract
ants with extra-floral nectary
secretions, but the ants do not nest.
The Acacia species on the left
increase their nectar secretions after
damage, inducing wandering ants to
come visit and stay a while.
The species on the right have to
support the ant colonies all the time,
and nectar production is uniformly
high and unaffected by damage.
WHICH CAME FIRST??
Induced and Constitutive Defenses in Acacia.
Induced defenses first,
then the obligate
relationship evolved…
Todd M. Palmer, Maureen L. Stanton, Truman P. Young, Jacob R. Goheen, Robert M.
Pringle, Richard Karban. 2008. Breakdown of an Ant-Plant Mutualism Follows the Loss
of Large Herbivores from an African Savanna. Science 319:192-195.
Fig. 1. Rewards produced in the presence
(white bars) and absence (gray bars) of
large herbivores by A. drepanolobium
occupied by different species of Acacia
ants. Ant species' abbreviations are
indicated as: Cs, C. sjostedti; Cm, C.
mimosae; Cn, C. nigriceps; Tp, T. penzigi.
Plants produce fewer rewards and
fewer thorns when large herbivores are
absent and herbivory rates are LOWER.
Bribing ants to stay and protect them is
less important.
Todd M. Palmer, Maureen L. Stanton, Truman P. Young, Jacob R. Goheen, Robert M.
Pringle, Richard Karban. 2008. Breakdown of an Ant-Plant Mutualism Follows the Loss
of Large Herbivores from an African Savanna. Science 319:192-195.
Fig. 2. The proportion of host
trees occupied by the four
Acacia-ant species in the
presence of large herbivores
(white bars) and in plots from
which large herbivores had
been excluded (gray bars) for
10 years.
And if large herbivores are
excluded and plants produce
less nectar, then some ants
abandon the trees (the
mutualist).
“Our results indicate that the large herbivores typical of African savannas
have driven the evolution and maintenance of a widespread ant-Acacia
mutualism and that their experimentally simulated extinction rapidly tips the
scales away from mutualism and toward a suite of antagonistic behaviors
by the interacting species. Browsing by large herbivores induces greater
production of nectary and domatia rewards by trees, and these rewards in
turn influence both the behavior of a specialized, mutualistic ant symbiont
and the outcome of competition between this mutualist and a non-obligate
host-plant parasite. Where herbivores are present, the carbohydrate
subsidy provided by host trees plays a key role in the dominance of the
strongly mutualistic C. mimosae, which is consistent with the hypothesis
that plant exudates fuel dominance of canopy ant species that are
specialized users of these abundant resources (28). In the absence of large
herbivores, reduction in host-tree rewards to ant associates results in a
breakdown in this mutualism, which has strong negative consequences for
Acacia growth and survival. Ongoing anthropogenic loss of large herbivores
throughout Africa (29, 30) may therefore have strong and unanticipated
consequences for the broader communities in which these herbivores
occur.”
Todd M. Palmer, Maureen L. Stanton, Truman P. Young, Jacob R. Goheen, Robert M.
Pringle, Richard Karban. 2008. Breakdown of an Ant-Plant Mutualism Follows the Loss
of Large Herbivores from an African Savanna. Science 319:192-195.
Defensive Mutualisms – Trade protection for food
Ants ‘farm’ aphids and drink their ‘honeydew’
Cleaning Mutualisms – Trade cleaning for food
Cleaning Mutualisms – Trade cleaning for food
Cleaning Mutualisms – Trade cleaning for food
Fish visit non-cheating
cleaners more
And watched cleaners
cheat less.
Dispersive Mutualisms – Trade dispersal for food
Dispersive Mutualisms – Trade dispersal for food
Dispersive Mutualisms – Trade dispersal for food
Not mutualism
(commensal or
parasitic)
Mutualisms in Mimicry:
“Mullerian” mimicry – toxic species resemble one another
Population Ecology
I. Attributes
II.Distribution
III. Population Growth – changes in size through time
IV. Species Interactions
V. Dynamics of Consumer-Resource Interactions
VI. Competition
VII. Mutualisms
VIII. Evolutionary Responses to Species Interactions
Why won’t this population unit end?
Population Ecology
I. Attributes
II.Distribution
III. Population Growth – changes in size through time
IV. Species Interactions
V. Dynamics of Consumer-Resource Interactions
VI. Competition
VII. Mutualisms
VIII. Evolutionary Responses to Species Interactions
The abiotic environment is often stable, or at least predictable. Other
species in the environment are always changing, sometimes as a direct
result of changes in other species.
“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!”
A. Coevolution in Consumer-Resource Relationships:
One species is evolving to ‘escape’ the relationship, the other to enhance it.
“Arms Race”
- crypsis and detection
Predation
Coevolution in Consumer-Resource Relationships:
One species is evolving to ‘escape’ the relationship, the other to enhance it.
“Arms Race”
- crypsis and detection
Coevolution in Consumer-Resource Relationships:
One species is evolving to ‘escape’ the relationship, the other to enhance it.
“Arms Race”
- crypsis and detection
Coevolution in Consumer-Resource Relationships:
One species is evolving to ‘escape’ the relationship, the other to enhance it.
“Arms Race”
- crypsis and detection
Coevolution in Consumer-Resource Relationships:
One species is evolving to ‘escape’ the relationship, the other to enhance it.
“Arms Race”
- crypsis and detection
Coevolution in Consumer-Resource Relationships:
One species is evolving to ‘escape’ the relationship, the other to enhance it.
“Arms Race”
- crypsis and detection
Coevolution in Consumer-Resource Relationships:
One species is evolving to ‘escape’ the relationship, the other to enhance it.
“Arms Race”
- poisons and detoxification
Coevolution in Consumer-Resource Relationships:
One species is evolving to ‘escape’ the relationship, the other to enhance it.
“Arms Race”
- poisons and detoxification
Coevolution in Consumer-Resource Relationships:
One species is evolving to ‘escape’ the relationship, the other to enhance it.
“Arms Race”
- poisons and detoxification
Coevolution in Consumer-Resource Relationships:
One species is evolving to ‘escape’ the relationship, the other to enhance it.
“Arms Race”
- poisons and detoxification
Coevolution in Consumer-Resource Relationships:
One species is evolving to ‘escape’ the relationship, the other to enhance it.
“Arms Race”
- Mimicry
“Batesian” mimicry – palatable mimic looks like a toxic/dangerous model
Plant “crypsis” and “mimicry”
Heliconius and Passiflora
Plant “crypsis” and “mimicry”
Heliconia and Passiflora
Host-pathogen “arms races”
B. Evolution of Competitors
- competitive ability can evolve
- can result in character displacement
No positive feedback
Competition
A. Coevolution in Consumer-Resource Relationships:
B. Evolution of Competitors
C. Coevolution of Mutualists
Positive, coevolutionary feedback.
Mutualism
A. Coevolution in Consumer-Resource Relationships:
B. Evolution of Competitors
C. Coevolution of Mutualists
D. Relationships Change
A. Competition
Facilitation
Initially facultative (commensal) relationships,
like one plant shading another in the desert)
can become competitive when they are large.
A. Competition
Facilitation
Trees may compete for light aboveground, but
share nutrients via mycorrhizal fungi
belowground – even between species
A. Competition
Facilitation
Old dieing trees shunt nutrients to younger
trees – even between species- through
mycorrhizal networks. May be change in
relationships with the fungus, whereby ‘old
tree’ is being parasitized while young tree is
being facilitated. Net result is shunting of
carbon.
Mutualism
Parasitism
Orchids, Euglossine Bees, and Wasps.
B. Mutualism
Parasitism