Flashcards in Lecture 5 & 6 Symbiosis and mutualism (species interactions) Deck (18)
occur between individuals of the same species
occur between two or more species
definition and examples of symbiosis
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.
what is mutualism?
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.
what is commensalism?
A long-term close association between two species in which one benefits and the other in unaffected
what is parasitism?
A long-term, close association between two species where one benefits and the other is negatively affected/harmed
What is competition?
(-/-) Organisms of two species share the same limited resource and have a negative impact on each other
What is predation?
(+/-)A member of one species eats all or part of the body of am member of another species or prey
case study for mutualism:
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)
case study of commensalism:
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
obligate mutualism and case study:
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.
facultative mutualism and case study:
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)
nemo & anemone are not completely dependent.
What are different classes of mutualisms aside from obligative and facultative? (3)
What is a downside of mutualisms?
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.
Give an example of a mutualist withdrawing rewards:
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)
what are the ecological consequences of positive interactions? provide an example
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)
Summarise the lecture:
• 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.