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Exploitation (Ch. 14)
http://www.youtube.com/watch?v=
-drpViV5LSw&feature=related
They Infect You!
…and the animals and plants you depend on!
Microparasite Example (Malaria)
• Plasmodium spp. (5 human)
• Complex Life History (2 hosts)
– Intermediate- required for life
cycle but no sexual reproduction
occurs (humans)
– Definitive- where parasite is
sexually mature (mosquito)
• 40% population at risk
• 300-500 million infected, 1-3
million dead
Location on/in the Host Matters
• Ectoparasite: outside
host
– Ex. parasitic plants,
mites, ticks
• Endoparasite: inside
host
– Ex. tapeworms,
bacteria, protists
Cost/Benefit of Host Habitat
Feeding (acquire food)
Vulnerability to Predation
Environmental Stability
Exposure to host immune system
Dispersal
Ectoparasite
Endoparasite
Harder
EASIER
Higher
LOWER
Lower
HIGHER
LOWER
Higher
EASIER
Harder
Parasites Influence Other Interactions
• Can influence host reaction to other
species!
Adelina tribolii (Protozoan)
Tribolium castaneum
Tribolium confusum
Can You Tell the Difference?
T. castaneum
T. confusum
Percent Winning
Effects of Parasite Greater on the Better
Competitor, T. castaneum!
(Park, 1948)
Widespread Interactions
• Many interactions in food
webs are exploitations
• Provide many links: 500
aquatic species in a lake
may be linked by 25,000
exploitative interactions!
Evolutionary effects……
Red Queen Hypothesis
• "Now, here, you see, it
takes all the running you
can do, to keep in the
same place.”
– Lewis Carroll (Through
the Looking Glass)
Red Queen Hypothesis
1) Hosts constantly evolve
to fight off parasites.
2) Parasites evolve to
exploit host
3) Failure to “keep up:”
extinction!
Red Queen Hypothesis
Coevolution: Evolution
caused by the other
species and vice versa.
Evolutionary “Arms Race”
Nuclear weapons…
Australian Problem
• Who am I?
Native range Spain, Portugal, NW Africa
Australian Problem
• "The introduction of a few rabbits
could do little harm and might
provide a touch of home, in
addition to a spot of hunting.”
• Australian rancher Thomas Austin
(1859)
Biocontrol??
Australian Rabbit Problem
• 1950 Myxoma virus
introduced to naïve (no
previous exposure)
rabbits:
Lethality decreased (transmission
max. for level III)
Coevolution between rabbits and virus
What about us?
• “Sweaty T-Shirt Experiment” (1995)
• 44 males wore t-shirt for 2 nights
• Women ranked smells of 7 t-shirts (3 Similar, 3 different, and 1
unused)
Red = Dissimilar, Orange = Similar
http://www.youtube.com/watch?v=-drpViV5LSw&feature=related
Adaptive Immunity
• Major histocompatibility
complex (MHC):
Hundreds of alleles
• U want to be different!
Why?
• Mates choose most
different mate (due to
smell) in mice, birds, fish
and lizards
Parasites That Alter Host Behavior
• Enslaver parasites:
alter host behavior to
increase reproduction
• Often causes host
death
• Increases parasite
dispersal
Nematomorpha
• http://www.nature.com/nature/journal/v440/n7085/suppinfo/440756a.html
Supplemental 1
Japan: 60% of
annual calories to
trout from
suicidal crickets!
b, c, d, show worm
escaping after predator
eats host!
Adult worms live/mate in water
Larvae encyst on vegetation near water
Parasites That Alter Host Behavior
• Acanthocephalan, terrestrial isopod, starling
Detritivore!
Parasites That Alter Host Behavior
• Isopod behavior suicidal...
• 1% Armadillidium infected, but 40% starlings!
Plants affected too!
• Rust fungus Puccinia manipulates mustard
(Arabis spp.).
– Puccinia infects Arabis rosettes
– Rosettes elongate, topped by cluster bright yellow
leaves. “Pseudoflowers”
Rosette of leaves
Parasites That Alter Host Behavior
• Pseudoflowers: sugary fungal reproductive fluids
• Pollinators move reproductive cells to other
pseudoflowers
Mmmmm,
fungal fluids….
Final Example…Zombie Snails!
•
http://www.youtube.com/watch?v=EW
B_COSUXMw&feature=related
• Take parasitology with Dr.
Sundermann (BIOL 5110)
Mutualism
(Ch. 15)
5 main types of interactions among species:
Effect on
species A
Effect on
species B
Competition
-
-
Predation
+
-
Parasitism
+
-
Commensalism
+
0
Mutualism
+
+
Type of interaction
Mutualism
• Mutualism: Interaction benefits both
• (+,+) interaction.
– Facultative Mutualism: can live w/o mutualist
– Obligate Mutualism: dependent on mutualist
Mutualism
• Margulis and Fester.
• Endosymbiotic theory: eukaryotes mutualism
between prokaryotes and eukaryotes
Margulis
“Life did not take over the globe by
combat, but by networking”
Mutualism
Mutualisms
• Classified based on benefit
– Trophic: provide food, water, etc.
– Dispersive: help organism move
– Defensive: protect against enemy
• Ex: moth pollination of flowers
• Moth: ___________ (nectar)
• Plant: _________ (pollen moved)
Pollination
• Interesting story: nectar spur of orchids (long tube at
bottom of which is nectar)
Fringed orchid
Pollination
• Long spurred flowers reproduce better
• Leads to longer tongues….
• Which leads to longer tubes......
Pollination
• Angraecum orchid (Madagascar). Darwin predicted
moth. Found after 40 years searching!
Nectar spur almost
1 foot long!
Plants + Mycorrhizal Fungi
• Mycorrhiza: root and fungus (mycorrhizae is plural)
• Plant trophic: increases uptake P and other immobile
(don’t move well from soil to root) nutrients
• Fungi get sugars (trophic)
Plants + Mycorrhizal Fungi
• Common types mycorrhizae:
– Arbuscular mycorrhizal fungi (AMF)
• Produces arbuscules (site of exchange between plants and
fungi), hyphae (fungal filaments)
– Ectomycorrhizae (ECM)
• Forms mantle around roots
Mycorrhizae and Plant
Water Balance
• Ex: water relations Agropyron
smithii (western wheatgrass)
Mycorrhizae and Plant
Water Balance
• With mycorrhizae higher leaf water
potentials
• 90% plant species
have mycorrhizae!
Ants and Bullshorn Acacia
• Acacia: trees/shrubs (legume family).
• Hollow spines (spine=modified leaf pointy thing)
Ants and Bullshorn Acacia
•
•
•
•
Leaves: extrafloral nectary (makes nectar but not flower)
Leaflets: Beltian Bodies (protein rich)
Ant benefit?
Plant benefit??
Experimental Evidence For
Mutualism
Acacia mutualism
• Benefits to plant (defensive):
– Ants predators
– Ants territorial
– Ants clear below shrub: removes
competitors, protects shrub (and ants!)
from fire