Endophytes epichlo ? fungus with sexual reproduction

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Endophytes -  Epichlo ë -->  Fungus (with sexual reproduction) has more genetic  variation / potential for evolution than host -->  Has the advantage in the  arms race
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Endophytes -  Epichlo ë However, some recently- evolved  Epichlo ë   species  are asexual themselves Hybrids of other  Epichlo ë   spp.   (?) Don t form stromata Completely symptomless Host flowers normally
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Endophytes -  Epichlo ë Non stroma-forming hybrid species are  transmitted from parent to offspring (= vertical  transmission) via infected seed No horizontal transmission Endophyte hyphae in  the aleurone layer of  a grass seed
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Endophytes -  Epichlo ë Non stroma-forming species are mutualistic Provide the host plant with chemical defenses against  herbivores not produced, or produced in much smaller quantities, by  stroma-forming species Alkaloids of fungal origin
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Effect of endophyte-infected sleepygrass on horses
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Endophytes -  Epichlo ë In this case, evolution of mutualism from  parasitism is linked with loss of horizontal  transmission Fitness of asexual fungus depends on seed  production by the host
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Life histories:  parasites vs mutualists Parasites Mutualists Transmission: horizontal often vertical Reproduction: sexual often asexual Dispersal   ability: high low Host   specificity: low high
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Communities:  Food webs Ch. 17
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Fig. 17-3
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Predation between  trophic levels AND  competition within  each trophic level -->  complex interactions A disturbance that directly affects one  species may have difficult-to-predict  domino effects on other species Food webs
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Example: Intertidal community, N.W. United States Producers:   Sargassum   (left) and  Ulva  (right) Food webs
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Herbivores =  Limpets  clockwise from left: Lottia digitalis, L. pelta, L. strigatella Lives on goose barnacles Lives on mussels Lives on both Intertidal community, N.W. U.S.
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Limpet-associated species: Goose barnacles (left) and mussels (right) Intertidal community, N.W. U.S.
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Carnivores: Seagull (left) and oystercatcher (right) Feed on goose barnacles and their associated limpet  ( L. digitalis ) Intertidal community, N.W. U.S.
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Experiment:  remove birds from the food  chain by constructing cages ( exclosures Predictions :   1. Barnacles   (removal of predator) 2. L. digitalis    (removal of predator) 3. Mussels   (increased competition from barnacles) 4. L. pelta     (reduction of host population) Intertidal community, N.W. U.S.
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When birds are excluded from the intertidal community, barnacles increase in abundance at the expense of mussels (predictions 1 and 3 supported).
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  • Winter '15
  • jane smith
  • Diversity index, Measurement of biodiversity, Shannon index, Ahmic Lake

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