Lec 23- Mutualism and Parasitism Flashcards
mutualism
++
- symbiotic
- plants: benefit from mycorrhizae through increased nutrient uptake in soil (+) - vital in poor nutrient or arid soil
commensalism
0+
- barnacles and whales
- barnacles: benefit from substrate and dispersal provided by whales (+)
- whales: no benefit and no harm (0) - facilitate the dispersal of barnacles
exploitation
-+
mycorrhizae
crop and forest productivity
ecosystem functioning
insects
crop pollination
honey production
pollinator networks
parasites
diseases
parasitism
beneficial to one and detrimental to other (exploitation)
- tick: benefit by feeding on blood in animals (+) - Lyme disease
- host: harmed through blood removal and disease risk
parasitic relationship
parasites engage with various organismal groups
- very host-specific
- all organisms encounter parasites throughout life
- mistletoes, tongue-eating lice, tapeworms, ticks
parasite-host relationship
share characteristics with predator-prey and herbivore-plant relationships (exploitative interactions)
- plant fungal parasite and herbivore reducing plant biomass
- parasite forms an intricate and long-term relationship with host
symbiosis
intricate and long-term living of 2 organisms
- Heinrich Anton de Bary
- commensalism. mutualism, parasitism
- very species-specific
- gradients and contingent on env. factors
can parasites alter behavior of host to their favor?
yes
- European starling (host)
- isopods
- thorny-head parasitic worms Plagiorhynchus
Crustacean isopod = Plagiorhynchus intermediate host (parasite grows here but doesn’t reach sexual maturity)
European starling = Plagiorhynchus definite/primary host (parasite reaches adult stage and sexual maturity)
Red Queen hypothesis
- species have to evolve to keep up with the evolution of their parasites and vice versa
- perpetual coevolution between the two can be compared to an arms race
“It take all the running you can do, to keep in the same place”- Lewis Carroll
mutualistic interactions
corals and zooxanthellae
lichens: fungi and algae
plants and mycorrhizal fungi
coral bleaching
caused by:
- change in ocean temp
- runoff and pollution
- overexposure to sunlight
- extreme low tides
- physiological stress causes the loss of pigments and more susceptibility to disease
mycorrhizal fungi (MF)
symbiotic relationship b/w fungus and plant associated with plant roots in soil
- arbuscular mycorrhizal fungi (AMF): penetrate cortical cells of plant roots, 80% of plant spp.
- ectomycorrhizal fungi (EMF): no penetration to cortical cells, 2% of plant spp.
some do not have MF
mycorrhizae
AMF more mutualistic when grown in nutrient poor soil
- Nancy Johnson
mycorrhizae form a mutualism-parasitism continuum
only beneficial for fungi
- plant grown with and without AMF and calculated percentage change of biomass with AMF and with the control
- experiment showed that plant-AMF relationships form a continuum from mutualistic to parasitic interactions
mutualism-parasitism continuum
- net effects of cost/benefits
- mutualism to reciprocal parasitism
(= natural selection should favor a species own fitness rather than simply to “help” organisms)
++: beneficial for the plant plant provides carbs to fungus and receives nutrients
+,-: detrimental for plant: plant provides carbs to fungus but does not receive nutrients
non-symbiotic mutualism
not all mutualistic interactions are intricate (“constant body to body”)
pollination
transfer of pollen grains for repro by wind, water, animals or within same flower (selfing)
animals as pollen dispersal vectors
plant species that rely on animals for pollen dispersal often have very specific pollinators that they have coevolved with
attracting pollinators
color and scent
- butterflies: attracted to bright colors (yellow, orange, red): red-blind, attracted to yellow or blue
- nocturnal moths: attracted by heavy-scent released during night
rewarding pollinators
pollen, nectar or prospect to mate with a female
facultative vs obligate mutualisms
facultative = occurring optionally
no dependence on specific partners (low risk of extinction if partner goes extinct)
obligate = occurring by necessity
dependence on specific partners (high risk of extinction if a partner goes extinct)
what do pollinators provide?
ecosystem services
bees as commercial pollinators
1/3 of global food production due to pollination
30 billion dollars US/year
facilitated by managed pollinators
bees in decline
colony collapse disorder (CCD)
- colonies lacking worker bees and cannot sustain themselves despite abundant honey
- 30% loss each winter which is 3x higher than normal (06)
- parasites, pesticide, poisoning, stress, inadequate forage
- native bumblebees decline
measures to counteract pollinator loss
flower strips counteract pollinator loss
increasing landscape heterogeneity
