Societies, mutualists, & parasites - part 1

Question 1

define Mutualism

Answer 1

• Reciprocal adaptations in two or more species that benefit all species
• it is a +/+ interspecific ecological interaction

Question 2

Key components of mutualistic (and parasitic) relationships

Answer 2

1. Identifying partners
2. Types of partners
3. Strength of partnership
4. Complexity of partnership
5. The breakdown of mutualistic partnerships

Question 3

If mutualism involves reciprocal adaptations in two or more species, how might we identify possible mutualisms?

Answer 3

Mutualisms need to be identified by showing the reciprocal value of species traits for fitness of all putative partners.

Question 4

identifying mutualism partners: plants and ants

Answer 4

• Specific plant traits attract and reinforce relationship with nesting and foraging ants.
• example: The evolution of extrafloral nectaries (EFNs)

Question 5

extrafloral nectaries (EFNs) experiment

Answer 5

• Experimental access to plants with functional and non-functional (control) EFNs
• Colonies all started with the same composition and had the same diet, including simple sugar solution

Question 6

extrafloral nectaries (EFNs) experiment - result

Answer 6

colonies with access to EFNs, produced more queen biomass, more soldiers, and more eggs

Question 7

types of mutualistic partners

Answer 7

• Societies with other societies
• Societies with solitary animals
• Societies with plants
• Societies with single-celled organisms.

Question 8

types of mutualistic partners - societies with other societies example

Answer 8

ant-aphid tending

Question 9

types of mutualistic partners - societies with solitary animals example

Answer 9

ant-bug farming

Question 10

types of mutualistic partners - societies with plants example

Answer 10

ant-plant mutualisms

Question 11

types of mutualistic partners - societies with single celled organisms example

Answer 11

trophic mutualisms with bacteria

Question 12

societies with single celled organisms - bacteria mechanisms examples

Answer 12

• Bacteria can break down plant material
• Bacteria can recycle waste nitrogen

Question 13

how can the strength of a mutualism can be measured as

Answer 13

• Extent to which mutualism is facultative vs. obligate for both partners.
• Quantitative magnitude of the benefits derived from the interaction by both partners.

Question 14

Facultative mutualism example

Answer 14

• Feeding on plant nectar by ants is opportunistic.
• Ants do not nest on the plant.
• Plants only produce nectar at certain times of the year.
• Partners derive benefits but can survive and reproduce without the interaction.

Question 15

Obligate mutualism example

Answer 15

Ants nest solely in living plant structures and derive most of their food from the plant, while the plant requires year round protection to reproduce.

Question 16

obligate mutualism - Whistling-thorn Acacia and their mutualistic ants

Answer 16

• Ants provide year around protection
• Including protection from herbivores (especially elephants)
• plant is required for reproduction of ant colony

Question 17

obligate mutualism: whistling-thorn acacia - How do ants defend a tree against elephants?

Answer 17

Ants bite the inside of a trunk of an elephant

Question 18

Obligate mutualism: plants, ants, and elephants - two main experiments

Answer 18

• feeding trials
• tree survival and ant density

Question 19

elephant experiments - feeding trials

Answer 19

Shows the there is almost no consumption where ants are present

Question 20

elephant experiments - tree survival and ant density

Answer 20

• Shows just having even a few ants can result in a smaller number of browsed branches
• No ants result in the highest damage on the plant

Question 21

Complexity of mutualism partnership

Answer 21

• not all mutualisms are one-to-one
• not all mutualism partners are the same
• different mutualism partners might be co-dependent on each other

Question 22

complexity of mutualism partnership - not all mutualisms are one-to-one

Answer 22

• In facultative mutualism, many-to-many relationships are common
• Even if a paired mutualism is obligate, other partners may exist (i.e. one-to-many relationship)

Question 23

complexity of mutualism partnership - not all mutualism partners are the same

Answer 23

• When multiple partners exist, they are unlikely to yield the same benefits
• some partners are preferred more than others

Question 24

complex of mutualism partnership - Different mutualism partners might be co-dependent on each other.

Answer 24

Mutualism may exist as an interaction web, not a simple pairing.

Question 25

not all mutualism partners are the same example

Answer 25

Whistling-thorn acacia tree species

Question 26

whistling-thorn acacia tree species - how many ants are on the tree?

Answer 26

Whistling-thorn acacia tree species actually has four common ant species that may be resident on individual trees within the population (only ever one ant species per tree).

Question 27

whistling-thorn acacia tree species - is there any ant species that are preferred?

Answer 27

• Yes, one ant species provides significantly better protection than the other three
• one of these three tends towards a parasitic relationship.

Question 28

Mutualisms in complex interaction webs - What’s the big mutualism that leaf-cutting ants are involved in?

Answer 28

leaf-cutting ants has a trophic mutualism with a specific fungus

Question 29

mutualisms in complex interaction webs - What might be one of the big challenges of relying on a single crop species (aka monoculture) for all of the leaf-cutting ants colony’s nutrition?

Answer 29

• Mutualistic fungus gets attacked by specialized parasitic fungus and the entire garden can be wiped out
• like many monotypic crops

Question 30

mutualisms in complex interaction webs - how has leaf-cutting ants evolved to combat the downside of monoculture

Answer 30

Leaf-cutting ants have evolved a secondary defensive mutualism with bacteria that combats the fungal parasite