PARENT SESSION
Oral Session #18: Herbivory: Folivory and rhizovory.
Presiding: A. Stephenson
Monday, August 5. 1:00 PM to 3:45 PM. Apache Meeting Room, TCC.
Soil fungi affect the compensatory response of Centaurea maculosa to shoot and root herbivory.
Newingham, Beth*,1, 1 University of Montana, Missoula, MT
ABSTRACT- Plant communities can be influenced by top down effects of herbivores and bottom up effects of AM fungi. However, ecologists rarely examine how herbivores and AM fungi interact to affect plant performance. I investigated the role of competing plants and soil fungi in the response of the invasive plant, Centaurea maculosa, to damage by the root borer, Cyphocleonus achates, or the shoot herbivore, Trichoplusia ni. Centaurea maculosa was planted either alone or with Festuca idahoensis in the presence or absence of soil fungi. Competition by F. idahoensis had no effect on C. maculosa, but C. maculosa had a negative effect upon F. idahoensis. Herbivory did not affect C. maculosa and there was no difference between shoot and root herbivory. Contrary to previous results, soil fungi had a negative effect on C. maculosa and Festuca idahoensis. In addition, soil fungi determined the compensatory response of C. maculosa to herbivory. When soil fungi were present, herbivory had no effect upon C. maculosa; whereas, when soil fungi were absent, herbivory had a positive effect on C. maculosa. The negative effect of soil fungi may be due to high costs of mycorrhizal associations, the species of fungi present, or soil pathogens. These results suggest mycorrhizal fungi may have a negative rather than a positive effect upon plant compensatory responses to herbivory.
KEY WORDS: Centaurea maculosa, herbivory, AM fungi, invasion