Ecology Ch.13

What is a parasite?

Organisms that feed on but (typically) don’t kill host

Often directly remove nutrients from hosts, but not necessarily biomass

What is endoparasitism and its advantages?

Endoparasitism is feeding on the inside of the host

advantages: ease of feeding, protected from external environment, safer from natural enemies

disadvantages: vulnerable to host immune system, harder dispersal

What is ectoparasitism?

Feeding on the outside of the host

advantages: ease of dispersal, safe from the immune system

disadvantages: feeding is more difficult, exposure to the external environment, vulnerability to natural enemies

How do parasites affect host reproduction?

Infect populations have lower chance of successful eggs because of fewer resources

How do parasites affect the outcome of competition?

How do parasites affect distribution of species?

Parasites can limit distribution. Fungus completely eradicated the American chestnut trees

Describe parasite host coevolution

Parasite modify host life cycle/ behavior to increase the chances of them completeing their life cycle

Hosts can evolve resistance —> Parasite evolves work around —> Red Queen Hypothesis

coevolution

Example:mimicing host antigens. Parasite, Psuedomonas syringae produces coronatine. Coroatine mimic the plant hormoen jasmonic acid and suppresses the plant immune response.

What are examples of parasites causing coevolution?

Example 1 : mimicking host antigens. Parasite, Psuedomonas syringae produces coronatine. Coroatine mimic the plant hormoen jasmonic acid and suppresses the plant immune response.

Example 2: European Rabbits and Myxoma virus. Myxoma virus was introduced to reduce populations of invase rabbit, but the virus became less lethal over time.

Example 3 : Parasites better able to affect hosts they are familiar with compared to new hosts

Example 4: parasites infect common host genotypes more easily than rare genotypes

what are the ecological effects of parasites?

Parasites can alter physical environments

Corophium is an ecosystem engineer in mudflat- burrows to prevent erosion

Trematodes can drive Corophium to extinction increased erosion)

Parasites that are associated with their hosts over evolutionary times co-speciate(have similar phylogenies)

Describe the dynamics and spread of disease

pNh = encounter rate

Np= percentage of successful predation

rNh= population growth

B= transmission coefficient

S= susceptible

I= infected

m=death

What are parasitoids?

Feed on the host throughout their life cycle, which usually kills their host.

Parasitoids are exclusively insects.
Wasps lay eggs in host and larva consume the still living host to pupate and emerge