Ecology Exam 3 Chapter 15

mutualism

interactions between individuals of different species that benefit both partners

commensalism

interactions between two species that benefits one and is neutral for the other

facultative mutualism

species can live withouth their mutualistic partners

obligate mutualism

species cannot live without their mutualistic partners

without mutualism

No biosphere

all hetero and autrophic eukaryotes

originated as mutualistic associations between different organisms

white-tailed deer (adocoileus virginianus)

breaks down cellulose provides place for bacteria to live

example of commensalism

turkeys in trees; provides shelter for turkeys and trees unchanged)

red-billed oxpecker (B. erythrorhynchus)

NOT mutualism; deer are agitated by oxpeckers; spent most of their time eating dead skin earwax and open wounds; tick load increased with oxpeckers

acacia trees and ants pseudomyrmex

giant herbivores can harm acacias; most have thorns; acacia produces belshian bodies for ants to eat in exchange for defense from herbivores and insects

janzen experiment with acacias and ants

measured new growth with and without ants; grew much faster with ants; ants remove inter and intra specific competition; lowers predation rate

kathleen keeler

mutualism will evolve if: Wms+Wmu > Wnm

Wms

successful mutualists

Wmu

unsuccessful mutualists

Wnm

non-mutualists

unsuccessful mutualists

trees that produce structures for ants but not good enough for ants to live on

mutualism won’t evolve if

cost of trying but not succeeding is too high

Keeler’s conditions for the evolution and persistence of mutualism

pwms + qwmu > wnm

p keeler

proportion of the population consisting of successful mutualists

Wms keeler

 the fitness of successful mutualists

q keeler

the proportion of the population consisting of unsuccessful mutualists

Wmu

 the fitness of unsuccessful mutualists

selective cost of being a successful mutualist, an unsuccessful mutualist, or a nonmutualist

P[H(1-D)A]>Ia

P selective cost

frequency of successful mutualists

H selective cost

overall potential damage from herbivores

D selective cost

inaffectiveness of alternative defenses to herbivory

A selective cost

effectiveness of ant defenses

Ia selective cost

cost to the plant of investment in features for ants

mutualistic interactions are

common

lichens

have a fungus and photosynthetic algae component

theory predicts that mutualism will evolve if

the benefits of the interaction exceed the costs for the participating individuals