Chapter 17 - Mutualism

mutualism

ecological interaction where both species involved benefit from their relationship

parasitic vs mutualistic relationship

Mutualism – both species benefit. Parasitism – one species benefits while one is harmed

obligate vs facultative mutualists

obligate - 2species provide fitness benefits to each other AND require each other to persist

facultative - 2 species provide fitness benefits to each other BUT interaction isn’t critical to persistence of either species 

generalist vs specialist mutualists

generalist - species that interacts with MANY other species 

specialist - species that interacts with ONE other species or a few closely related species

example of mutualist providing resources

sharks provide cleaner fish with food source as parasites 

cleaner fish provide sharks with decreasing number of parasites 

example of mutualist providing defense

acacia trees provide ants with thorns they can hollow out for nests

ants provide defense through biting any herbivores that try to consume leaves

example of mutualist providing pollination

Bee lands in a flower - get some pollen on their hairy bodies then when they land in the next flower, some of the pollen from the first one rubs off, pollinating the plant

example of mutualist providing  seed dispersal 

Dung beetles roll the seed away and help the plant colonize new areas

how could specialist mutualist species be MORE vulnerable to becoming endangered

a specialist species may have become so dependent on a resource or relationship with another species that the loss of this connection will lead to extinction.

how can mutualist partners prevent the other species from “cheating” 

how could environmental conditions cause mutualism to switch to parasitism

host species actively reducing the benefit or imposing a cost on a "cheating" partner -  the hosts select for more cooperative partners

how can presence or absence of a mutualist cause change

mutualist is lost -

• the other partner is directly deprived of a vital service or resource

• a species may no longer be able to colonize or persist in habitats where it previously thrived

Mutualism is present

• partner's growth, survival, and reproductive success increase

• mutualist may indirectly benefit other species by providing resources or services

mycorrhizal fungi

a fungi that surrounds plant roots and helps the plant obtain water and nutrients

endomycorrhizal fungi vs ectomycorrhizal fungi

endomycorrhizal fungi - fungi that has hyphal threads that extend far out into the soil and penetrate root cells between the cell wall and membrane

ectomycorrhizal fungi - fungi that have hyphae that surrounds roots of plants and enter between root cells but RARELY enter the cells

4 ways to describe mutualists 

• generalist 

• specialist 

• obligate 

• facultative 

what is one of the most common functions of mutualistic relationships

help species acquire needed resources such as water, nutrients, place to live

explain the mutualistic relationship between plants and fungi

plants provide fungi with sugars

fungi provide plants with minerals and water from soil

what is an additional benefit fungi can provide plants with

increased resistance to drought and salt stress

which type of mycorrhizal fungi forms fewer mutualistic relationships 

ectomycorrhizal 

describe the mutualistic relationship between plants and bacteria

bacteria convert unusable forms of materials into forms plants can use (like N2 to ammonia)

plants - provide place for bacteria to live and products of photosynthesis

describe mutualistic relationship between animals and protozoan

protozoans: receive place to live within the animal AND a constant source of food

animals - gain nutrients from protozoan’s waste

describe mutualistic relationships between two animal species 

one animal: provides habitat 

second animal: provides reciprocal benefit 

what is key for seed dispersal

that the fruit remains inedible or hidden until the seeds within are fully developed

do individuals in mutualistic relationship participate to increase others fitness or their own 

their own 

when can a mutualistic relationship change to no longer be mutualistic

when the costs and benefits to each species change

how can a positive interaction change to a negative interaction (predation, herbivory, parasitism)

when one species provides benefit to the second species at a cost BUT they no longer receive a benefit in return

what is cheating

1 species receives benefit but doesn’t provide one in return

what is expected of the distribution of mutualism if favoured by natural selection

the distribution of mutualistic species would expand

what would happen to the mutualistic species’ distribution if the mutualism was disrupted

decline in species involved and distribution

does mutualism affect only the species involved

NO - has far reaching consequences through chain reactions