Lecture 5 & 6 Symbiosis and mutualism (species interactions)

Question 1

Intraspecific interactions

Answer 1

occur between individuals of the same species

Question 2

Interspecific interactions

Answer 2

occur between two or more species

Question 3

definition and examples of symbiosis

Answer 3

Two species that live together in a long-term, inimate association. Symbiosis is an interaction characterized by two or more species living in direct contact with each other. Symbiosis can be pos, neg or neutral.
mutualism (+/+)
commensalism (+/0)
parasitism (+/-)

Question 4

what is mutualism?

Answer 4

A long-term close association between two species in which both partners benefit, whether though shelter, food, transport etc Sometimes there is a cost to one or both partners, but the net effect is positive. These are common.

Question 5

what is commensalism?

Answer 5

A long-term close association between two species in which one benefits and the other in unaffected

Question 6

what is parasitism?

Answer 6

A long-term, close association between two species where one benefits and the other is negatively affected/harmed

Question 7

What is competition?

Answer 7

(-/-) Organisms of two species share the same limited resource and have a negative impact on each other

Question 8

What is predation?

Answer 8

(+/-)A member of one species eats all or part of the body of am member of another species or prey

Question 9

case study for mutualism:

Answer 9

CORAL - coral provides shelter and compounds for photosynthesis for zooxanthellae/photosynthetic algae. Algae provides food for coral in nutrient poor environments. (Muscatine and Porter, 1977) (also trophic mutualism)

Question 10

case study of commensalism:

Answer 10

Hermit crabs and anemones - anemones live on the claws on the hermit crab protecting the claws of the crab & mop up food & as body guards. less clear why anemone decides to live there. (Rittschof et al., 1999)
Whale and barnacles (difficult to show as commensalism as whales could be slowed down by barnacles or provided with camo from orcas)
Kelp - many organisms live on kelp and do it no harm

Question 11

obligate mutualism and case study:

Answer 11

interaction is not optional for either species.
Goby and shrimp. Shrimp are blind and gobys warn shrimp when leaving the burrow is unsafe. Goby get refuge from predation. (Lyons, 2013) (also habitat mutualism)
some species may co-evolve unique features that benefit eachother.

Question 12

facultative mutualism and case study:

Answer 12

the interacting species derive benefit from each other but not being fully dependent that each cannot survive without the symbiotic partner.
When mussels are present in seagrass meadows, they elevate seagrass productivity through either increased nutrient resource pools or reduced epiphytic loads on the leaves, while the seagrass increases mussel survivorship. (Peterson & Heck, 2001)
OR
nemo & anemone are not completely dependent.

Question 13

What are different classes of mutualisms aside from obligative and facultative? (3)

Answer 13

habitat mutualisms
tolerance mutualisms
trophic mutualisms

Question 14

What is a downside of mutualisms?

Answer 14

Although both partners in a mutualism benefit, there are also costs. e.g.In the coral–alga mutualism:
- cost to the coral includes supplying nutrients and space
- Cost to the alga is giving up some carbohydrates it could use for itself
net benefits must exceed net costs for both partners.
If environmental conditions change, and benefit is reduced or cost increased for either partner, the outcome may change, particularly for facultative interactions.

Question 15

Give an example of a mutualist withdrawing rewards:

Answer 15

In an obligate mutualism between a yucca and a yucca moth, the female moth collects pollen in one yucca and then lays their own eggs in another, depositing the pollen in this flower. Larvae complete development by eating the seeds in the flower. Cheating can occur if moths lay too many eggs and the larvae eat too many seeds.
But yuccas can selectively abort flowers with too many eggs before the moth larvae hatch
Plants turn off the production of seeds if there are too many eggs. (Powell, 1992)

Question 16

what are the ecological consequences of positive interactions? provide an example

Answer 16

In positive interactions when one specie provides a favourable habitat it influences the distribution of that other species e.g.
cora and alga, fig and wasp
Groups of dominant species commonly determine distributions of other species by providing habitat (trees, corals)

Question 17

Summarise the lecture:

Answer 17

• In positive interactions, neither species is harmed, and the benefits are greater than the costs for at least one species.
• Each partner in a mutualistic interaction acts in ways that serve its own ecological and evolutionary interests.
• Positive interactions affect the abundances and distributions of populations as well as the structure of ecological communities.

Question 18

case study for mutualism:
case study of commensalism:
obligate mutualism and case study:
facultative mutualism and case study:
Give an example of a mutualist withdrawing rewards:

Answer 18

(Muscatine and Porter, 1977)
CORAL - coral provides shelter and compounds for photosynthesis for zooxanthellae/photosynthetic algae. Algae provides food for coral in nutrient poor environments. (also trophic mutualism)
(Rittschof et al., 1999)
Hermit crabs and anemones - anemones live on the claws on the hermit crab protecting the claws of the crab & mop up food & as body guards. less clear why anemone decides to live there.
interaction is not optional for either species.
Goby and shrimp. Shrimp are blind and gobys warn shrimp when leaving the burrow is unsafe. Goby get refuge from predation. (Lyons, 2013) (also habitat mutualism)
some species may co-evolve unique features that benefit eachother.
the interacting species derive benefit from each other but not being fully dependent that each cannot survive without the symbiotic partner.
When mussels are present in seagrass meadows, they elevate seagrass productivity through either increased nutrient resource pools or reduced epiphytic loads on the leaves, while the seagrass increases mussel survivorship. (Peterson & Heck, 2001)
OR
nemo & anemone are not completely dependent.
In an obligate mutualism between a yucca and a yucca moth, the female moth collects pollen in one yucca and then lays their own eggs in another, depositing the pollen in this flower. Larvae complete development by eating the seeds in the flower. Cheating can occur if moths lay too many eggs and the larvae eat too many seeds.
But yuccas can selectively abort flowers with too many eggs before the moth larvae hatch
Plants turn off the production of seeds if there are too many eggs. (Powell, 1992)