Chap 15 parasitism and mutualism (cont.)

Mutualism

DEFINITION (RECAP):

- an interaction between members of two species that serves to benefit both parties involved

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TYPES OF BENEFITS (CAN VARY)

- provision of essential resources (food and shelter)

- may involve protection from predators, parasites, and herbivores

- may reduce competition with a third species

- may involve reproduction benefits such as dispersal of gametes or zygotes

obligate mutualists

cannot survive or reproduce with out the mutualistic interaction

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IS DIFFERENT FROM FACULTATIVE MUTUALISTS

Facultative mutualists

can survive or reproduce without the mutualistic interaction

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OPPOSITE OF OBLIGATE MUTUALISTS

Degree of specificity of mutualism

varies from one interaction to another

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TYPES OF MUTUALISTS:

- specialist mutualists

- generalist mutualists

specialist mutualists

ranges from one to one species-specific association

generalist mutualists

mutualist that associate with a wide diversity of mutualistic partners

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EXAMPLE:

- plant-animal pollinator systems

degree of intimacy

also varies among mutualistic interactions

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TYPES OF INTIMACY:

- nonsymbiotic

- symbiotic

Nonsymbiotic

free living individuals

symbiotic

individuals coexist and their relationship is more often obligatory

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FEATURES:

- at least one member of the pair becomes totally dependent on the other

- distinction between the two organisms becomes blurred

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EXAMPLE:

- Reef-forming corals

reef-forming corals

individual coral animals: polyps occupy little cups, or corallites, in the larger skeleton that forms the reef

zooxanthellae

the symbiotic algae in the reef-forming corals tissue

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FEATURES:

- can obtain 90% of its energy from the carbon produced by the symbiotic algae through photosynthesis

how are reef-forming corals symbiotic with algae

corals can provide the algae with shelter and mineral nutrients

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TYPES OF NUTRIENTS:

- nitrogen in the form of nitrogenous wastes

lichens symbiotic relationship between fungus and photosynthetic algae/cyanobacteria

- they are fused into a single body

- the fungus protects the algae from harmful light intensity

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BENEFITS:

- can produce a substance that accelerates photosynthesis in the alga

- can absorb and retain water and nutrients for both organisms

nonsymbiotic mutualism

2 organisms do not physically coexist

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BUT:

- they depend on each other for some essential function

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FEATURES:

- may be obligatory (but most aren't)

- they are facultative (doesn't involve the interactions between two species)

- involves a variety of plants, pollinators, and seed dispersal

digestive system of herbivores

is inhabited by a diverse community of mutualistic organisms

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SO WHAT?:

- they play a crucial role in the digestion of plant materials

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EXAMPLES:

- Ruminant mammals

Ruminant mammals

FEATURES (LEC)

- have a complex stomach with multiple chambers, which house bacteria and protists (mainly anaerobes) that can break down plant material

Which insects also rely on heavily on gut microbes for digestion

termites

Legumes

a group of plant species that have a symbiotic relationship with a type of nitrogen-fixing bacteria called Rhizobium

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FEATURES:

- are able to convert nitrogen gas into solid ammonia

- can secrete chemicals from their roots to attract rhizobia

Rhizobia

nitrogen fixing bacteria that enters the root hairs of legumes and multiply to increase in size

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LEADS TO

- the formation of rood nodules that house these bacteria

in some mutualism examples (LEC)

one species provides a resource that can be used as a defense by the second species

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EXAMPLE:

- Epichloe

Major problem for livestock producers

is the toxic/infecting effects of certain grasses

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PARTICULARLY

- perennial ryegrass and tall fescue

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EXAMPLE:

Fungi (clavicipitacceae and ascomycetes)

Fungi (clavicipitacceae and ascomycetes)

fungi that produce alkaloid compounds in the tissue of the host grasses

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FUNCTIONS:

- can make grass have a bitter taste which can be toxic to grazing mammals and insect herbivores (results to death if eaten)

acacia trees

FUNCTION:

- provides food and shelter for ants

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IF ACACIA TREE IS EVER DISTURBED BY INTRUDER:

- the ants will swarm out of the shelters, and emmit a repuslive oder and attack the intruder until it is driven away.

Cleaning mutualism

WHICH ANIMAL HAS THIS TRAIT?

- found between clearner shrimp or cleaner fishes

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HOW DO THEY BENEFIT FROM IT

- they can obtain food by cleaning ectoparasites and diseased and dead tissue from the host fish (allows for the removal of unwanted material)

Cross pollination

to transfer pollen from one individual to another of the same species

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WAYS POLLEN CAN BE TRANSFERED?

- wind

- animal pollinators

Wind (cross pollination)

ADVANTAGES:

- cost little when plants grow in homogenous stands

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DISADVANTAGES:

- range of dispersal distance is variable and is non specific

animal pollinators (cross pollination)

ADVANTAGES:

- more reliable direct transmission to another plant

- range of dispersal can reach to longer distances

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DISADVANTEGES:

- plants are more dependent on animals

- plant must use it energy to stay intact while being moved by an animal rather than grow

nectivores

Animals that feed on nectar

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HOW ARE THEY AN EXAMPLE OF ANIMAL POLLINATORS:

- nectivores pick up the pollen and carry it to the next plant they visit

Nectivores are

generalists that feed on may differnt plant species

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- nectivores depend on the progression of flowering plants through the season

types of "plant generalist"

- blackberries

- elderberries

- cherries

- goldenrods

plants being "specialist" (LEC)

flowers that attract or can be accessed by only one type of pollinator

seeds

can be dispersed by both types of cross-pollination

- wind

- animal

what features are seen in seed of plants that rely on animals for seed dispersal?

"Plants with seeds too heavy to be dispersed by wind depend on animals to carry them some distance from the parent plant and deposit them in sites favorable for germination and seedling establishment." (BOOK)

seed predators (seed dispersal)

Plants may also depend on these type of species

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WHY?

eating the seed will benefit the predator as they are gaining nutrients

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FACT:

- even if most seed are eaten some will survive

some plants

enclose their seeds in a nutritious fruit that attract fruit-eating animals (frugivores)

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plants that attract frugivores are considered as "mature seeds"

frugivores

fruit eaters

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FEATURES:

- are not seed predators because they eat only the fruit surrounding the seed

unripe fruits

contains immature seeds

- are often green (cryptic coloration example)

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FEATURES:

- may have a hard outer coat

- has a unpalatable texture to discourage consumption

ripe fruits

contain mature seed and may be colorful

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OTHER FEATURES:

- has a soft texture

- has an attractive odor smell

- has higher sugar and oil content to encourage consumption

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EXAMPLE:

- Coffee beans

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effect of mutualism on populations can be modeled

in a similar way to competition

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HOW?

- population growth rate will increase with increasing density of another intoduced species

- interaction will allow both populations to exist in higher numbers

How could you test for the effect of an obligate mutualism?

remove the population of one species and see if the population of the other species persists

facultative mutualism effects

are more subtle

- requires more detailed demographic data to determine the consequences for the fitness of each species

cases where mutualistic interaction is diffuse

can be challenging to determine the effect of interactions between particular species

mutualistic relationship between 2 species may involve

a 3rd species

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BENEFITS

- will facilitate or mediate the interaction

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SIMILARITES:

- much the same as for vector organisms and intermediate hosts in parasite host interactions

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EXAMPLE:

- mutualistic relationships between confers, mycorrhizae, and voles

clearing forests for agriculture and urbanization

has long been associated with declining plant and animal populations and the reduction of biological diversity

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- land use changes are directly impacting human health because they facilitate the expansion of infectious disease

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EXAMPLE:

- Lyme disease

Lyme disease

CAUSED:

- caused by a parasite bacterium called (borrelia burgdorferi)

- is transmitted by the bite of an infected black legged tick

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FACT

infectious disease that has been dramatically increased through out N Amer.

larval ticks (Lyme disease)

species that are uninfected when they hatch

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HOW DO THEY BECOME INFECTED?

- they feed on infected host animals

(host animal will most likely transmit the bacterium to the feeding tick)

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MOST COMMEN IN

- White footed mouse

forest fragmentation

involves the reduction in total forested area and reduction in the average size of remaining forest patches

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IMPACTS ON SPECIES:

- can have have a negative impact in species diversity (however some can thrive in this type of landscape)

Forest clearing and fragmentation

leads to a potential increase in the transmission of Lyme disease

deforestation

can lead to an increase in the prevalence of malaria

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INSECTS INVOLVED:

- parasite - protist

- vector - misquito

- host - humans

Facts about Malaria

- 40 % of the worlds population is at risk

- more than 2 million people die from it

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OTHER FIELD STUDY

- field study that occured in basin brazil showed similar results where deforestation from 1997 to 2000 associated with a 48% chance of getting Malaria.