ENT104 - Mutualisms (L16)

What is coevolution?

Reciprocal evolution

When one species evolves in response to another species

What are two strong cases of coevolution?

Arms races

Mutualisms

What are two weak cases of coevolution?

Parasites/Hosts, Predators/Prey

What type of ecological interaction results in BOTH species being harmed? (-, -)

Competition

What type of ecological interaction results in one species being harmed and the other unaffected? (-, 0)

Amensalism

What type of ecological interaction results in one species benefitting from harming another species? (-, +)

Exploitation

What type of ecological interaction has no effect on either species involved? (0, 0)

Neutralism

What type of ecological interaction results in one species benefiting without affecting the other species? (0, +)

Commensalism

What type of ecological interaction results in both species benefiting from each other? (+, +)

Mutualism

Pollinator systems, such as fig trees and fig wasps, are examples of _______

Mutualisms

(True/False)

Mutualisms are weak cases of co-evolution that benefit both parties

False

Mutualisms are very strong cases of co-evolution that benefit both parties

What are myrmecophytes?

Plants that have mutualistic relationships with ants

How do ants benefit from myrmecophytes?

Swollen thorns (domatia) provide ants with a home to raise larvae

Beltian bodies (such as proteinaceous bulbs) provide food for the ants

Extrafloral nectaries provide sugar for the ants

How do myrmecophytes benefit from ants?

Plants get protection from herbivores (such as beetles)

Plants get protection from competitor plants

What genus of ants commonly forms mutualistic relationships with Acacia trees?

Pseudomyrmex

What derived traits did Acacia ANTS evolve through their mutualism with Acacia trees?

Acacia ants are cathemeral (active during day & night)

Large colonies

Very aggressive to defend plant (have barbed sting sheath)

What derived traits did Acacia TREES evolve through their mutualism with Acacia ants?

Production of food and food structures for ants

Less defensive compounds

Fast growth

What happens when Acacia ants are removed from Acacia trees?

Plant growth rate decreases

Plants are less likely to survive

# of herbivorous insects on plants increases

How do pollinators manage to pollinate Acacia trees?

Young flowers produce a chemical deterrent that keeps ants away during key times when flowers are attractive to bees

Deterrent prevents ants from chasing away bees

What is ant herding?

When ants tend to aphids/scale insects/treehoppers/caterpillars for their secretions

Ant herding is a _________ interaction

Mutualistic

How do ants benefit from herding?

Tended insects secrete honeydew, which is rich in sugar and a good food source for ants

How do tended insects benefit from herding?

Protection from predators

Transport to better feeding sites

Removal of dead bodies and other waste (such as their own honeydew)

Why might ants prey on the insects they are tending?

Surplus of sugar

Ants need proteins and fats

When sugar needs are met, the ants see aphids as prey (a source of protein and fats)

(True/False)

Ants, plants, and aphids can co-occur and be mutualistic

True

Relationships between ants, plants, and aphids can be a combination of ______ and _______

mutualism and parasitism (exploitation)

How do plants benefit from aphids?

Aphids attract ants, and the ants protect both the aphids and the plants

In plants, what is the downside of keeping aphids?

Cost of feeding and potential disease

In plants, what is the downside of keeping ants?

Cost of producing homes (domatia) and food (Beltian bodies and extraflower nectaries)

What happens when a mutualistic relationship between ants, plants, and aphids becomes overwhelming for one or more partners?

Relationship could break down into only 2 partners involved (ants + aphids or ants + trees)

What plant discussed in lecture is found in West Africa and is a myrmecophyte?

Leonardoxa

(True/False)

Only Leonardoxa that do NOT produce extrafloral nectaries house both ants and scale insects

True

Extrafloral nectaries cut out scale insects from the tripartite mutualist relationship, as the ants no longer need the scale insects for a source of sugar

Why are coccids less effective than pseudococcids in their mutualist relationships with trees and ants?

Pseudococcids produce honeydew at a faster rate, allowing ants to be fed more efficiently

Ants that are fed faster then have more time to defend the insects and tree from predators

Coccids do not produce enough honeydew to outweigh the cost of feeding on the tree

How might coccids cause the mutualistic relationship between scales, ants, and trees to fall apart?

The cost of feeding the coccids outweighs the benefits of the ants defending the tree

The tree might put more resources into defending against the coccids instead of producing domatia

No domatia = no homes for ants

Without a home, the ants will no longer participate in the relationship. Without ants, the coccids no longer have protection from predators

Why might extrafloral nectaries evolve?

To cut out homopterans (aphids, scale insects) from the tripartite mutualist relationship (Ants/Trees/Homopterans)

It is less costly for the plants to feed ants directly rather than relying on homopterans to feed the ants (because homopterans feed on the plants and can be detrimental)

Mutualisms can sometimes degrade into ______

Parasitism