PARENT SESSION
Oral Session #91: Mutualisms -- Facultative, conditional, and complex.
Presiding: W. Wilson
Thursday, August 8. 1:00 PM to 3:45 PM. Cochise Meeting Room, TCC.

Nutrients and light control the population dynamics of plant-mycorrhizal symbiosis.

Umbanhowar, James^*,1, McCann, Kevin¹, ¹ Dept. of Biology, Montreal, QC, Canada

ABSTRACT- We construct a simple model of the symbiosis between plants and mycorrhiza to examine the impact of the two limiting resources of photosynthetic products and a general soil mineral nutrient. The first general result is that the limitation inherent in the ecosystem, both in incident light and total nutrient amounts, prevent runaway mutualism as predicted from simpler models. Adding nutrients to the soil generally reduced the strength of mutualism in the system. In symbioses where the plant could not limit the mycorrhiza, the added nutrients lead to mycorrhiza being parasitic, while plants exclude mycorrhiza when they can limit the amount of photosynthates that flow to mycorrhiza. We also demonstrate how trade-offs in investment and benefit in the symbiosis can allow for coexistence between competing plant species

KEY WORDS: Mututalism, Mycorrhiza, Population Dynamics, Competition