Another word for positive interactions
Facilitation
Mutually beneficial interaction
between individuals of two
species (+ / +
relationship)
Ex. Gut microbiota (plant mycorrhizae)
Mutualism
individuals of one species benefit; individuals of the other species do not benefit but are not harmed (+/0 relationship).
Ex. follicle mites
Commensalism
Two species live in close physiological contact with each
other.
• Symbioses can include parasitism
(+/–),
commensalism (+/0), and mutualism (+/+).
Symbiosis
Two major types of Mycorrhizae
Fig 15.4
Ectomycorrhizae
Arbuscular mycorrhizae
What does fungi help do?
Protect the plants from pathogens
Improve plant growth and survival
Supply plants with carbs
Corals form a mutualism
with symbiotic
algae
(zooxanthellae) by
The coral provides the alga with a home, nutrients and the alga with carbs
relationships that have coevolved where each organism depends on the other (not optional
Ex. fig and fig wasps
Obligate interactions
relationships that are optional (not obligate) and show few signs of coevolution
Ex. deer and seed dispersal
Facultative interactions
In a mutual interaction, the partners do what?
net effect is advantageous
Not altruistic
Take actions to promote their own best interests
Mutualist receives energy or nutrients from its partner
Ex. ants and fungus, mycorrhizae
Trophic mutualisms
One partner provides the other with shelter, living space, or favorable habitat.
Habitat mutualisms
One partner performs an ecological service for the other
ex. fig-fig wasp
Service mutualisms
In a mutualism, net benefits must exceed net costs for
both partners
n if the environment change and benefit is reduced or cost increase, outcome may change
Great-spotted cuckoos and carion crows went from parasitism to mutualism how?
Cuckoos are brood parasites – they
lay eggs in another species
nest for
them to raise.
• Canestari et al. showed that
this
parasitism can actually benefit the
crows in areas of
high predations
individuals that increase offspring
production by overexploiting
their mutualistic
partner.
occurs, interaction wont persist
Cheaters
The benefits from mutualism and commensalism can ultimately increase
growth, survival, or reproduction of the interacting species
How would you experimentally determine the
benefits that the
trees get from the ants?
set up plots with ants present and absent
and measure different
aspects of the acacia tree (abundance, size, percent mortality,
growth, etc
Fig 15.19 Many coral reef fish have service mutualisms with smaller
organisms (cleaners)
that remove parasites from
the fish (clients)
The benefit the client
receives is greater than the
energy
benefit it could gain
by eating the cleaner
Increase ocean temp can lead to
coral bleaching resulting in death
Bee colony collapse disorder (CC) threatens ecosystems dependent on
their pollination services