Fungal Endophyte Infection in an Alpine Meadow: Testing the Mutualism Theory
Cardou, F.. 2010. M.Sc. Thesis in Ecology University of Alberta
Abstract
Neotyphodium are fungal endosymbionts of grasses that reproduce asexually by
infecting the host's seed. This relationship has traditionally been considered
mutualistic, with the fungus improving host fitness by alleviating important
stresses. To determine the importance of biotic and abiotic stresses in mediating
the endophyte-grass interaction, Iinvestigated the relationship between grazing
pressure by collared pikas and Neotyphodium sp. infection frequency in the grass
Festuca altaicain an alpine meadow. I conducted a factorial design experiment
combining endophyte infection, grazing history, fungicide and fertilizer. Leaf
demography and herbivory damage were monitored every two weeks. In areas
with chronic grazing history,infected plants were significantly less productive
than uninfected tussocks, but there was no difference at low grazing history.
There was no effect of infection on the likelihood of herbivory. Contrary to
predictions of the mutualism theory, the Neotyphodiumsp. / F. altaica symbiotum
varied from parasitic to neutral across our gradient of interest.
