PARENT SESSION
Tuesday, August 8, 8:00-11:30 am
COS 20 - Food webs I: trophic interactions
Mississippi, Mezzanine Level, Cook Convention Center
Presiders: D Gruner

Interaction modification, tritrophic dynamics, and climate change: aphids, grass, and novel endophytes.

Neale, Amanda^*,1, Kerr, Jason¹, Lyons, Eric¹, Newman, Jonathan¹, ¹ University of Guelph, Guelph, ON, Canada

ABSTRACT- Atmospheric CO₂ is expected to dramatically increase by the end of the century. The increased CO₂ directly affects C₃ plant growth by creating a 'fertilization effect'. However, plants do not respond to CO₂ in isolation, but as part of a biotic community. In this study we investigate how the mutualistic relationship between tall fescue (Lolium arundinaceum) and its endophytic fungus (Neotyphodium coenophialum) respond to CO₂ and drought stress in the context of an aphid (Rhopalosiphum padi). Tall fescue that was either uninfected, infected with the common strain (CS) of endophyte or infected with a novel strain, AR542, were subjected to high and low drought stress at three different levels of nutrient supply. These treatment combinations were grown under three levels of CO₂: ambient, 500 and 600 ppm. We found that endophyte infected plants produced more dry matter than endophyte free plants when they were under increased CO₂ , plants infected with the novel endophyte did not out perform the endophyte infected plants but did out perform endophyte free plants. Aphid response was complex and non-linear. There was evidence for the following two-way interactions: CO₂ by drought; CO₂ by endophyte; CO₂ by nutrient; and endophyte by drought.

Key words: Trophic interactions, climate change, temperate grasslands