1
Today’s Outline
Ecology (BIOL 250)
Lecture 15: Mutualism!
Announcements
Mycorrhyzae
Cecropia
Bullhorn Acacia
Evolution of Mutualism s
Pollination
Coral
!Parasites live on host tissue and redu ce host fitness,
but do not generally kill the host.
!Mutualism: Interactions between individuals of different
species that benefit both partner s.
"Facultative Mutualism occurs when a species can liv e without its
mutualistic partner.
"Obligate Mutualism occ urs when a species is dependent o n a
mutualistic relationship.
!Two most common types of mycorrhizae:
"Arbuscular mycorrhizal fungi (AMF)
!Produces arbuscules - site of exchange between plants and
fungi, and hyphae - fungal filaments.
"Ectomycorrhizae (ECM)
!Forms mantle around roots - important in increasing plant
access to phosphorus and other immobile nutrients.
Mycorrhizae
!Allen and Allen studied water relations of grass
Agropyron smithii.
"Plants with mycorrhizae maintained higher leaf
water potentials.
!Plants with greater access to phosphorus may develop
roots that are more efficient at extracting and conducting
water.
Mycorrhizae
Plant Water Balance
Cecropia
Cecropia obtusifolia
Who might the mutualist b e?
!Herbivores attempting to forage on accacia
plants occupied by accacia ants are met by a
large number of fast, agile, highly-aggressive
defenders.
!Ant Benefits:
"Thorns provide living space.
"Folliar nectaries provide sugar.
"Beltian bodies are a source of oils and protein.
Bullhorn Acacia
