PARENT SESSION
Oral Session #53: Co-evolved species interactions: Mutualisms and parasitism. Presiding: A. Krist.
Wednesday, August 8, 2001. 1:00 PM to 4:45 PM. Hall of Ideas F.

Do plants selectively associate with species of ectomycorrhizal fungi that support highest plant growth?

KUMMEL, MIROSLAV¹, ¹

ABSTRACT- The hypothesis of this research is that plants, as a part of their foraging strategy, selectively associate with the species of ectomycorrhizal fungi (ECMF) that support the highest plant growth This hypothesis has three assumptions: 1) ECMF species differ in their effect on plant growth and thus the fungal species can be arranged in a growth-effect hierarchy, 2) the growth effect hierarchy changes between environments, and 3) the composition of ECMF is under at least partial control of the plant. These assumptions lead to the following predictions: 1) Each plant should selectively associate with the species of ECMF that supports the highest plant growth; and 2) the plant should selectively associate with different fungi in different environments, leading to 3) variation of ECMF with environmental conditions. Assumptions 1 and 2 and prediction 3 of the hypothesis are supported by the available published evidence. Predictions 1 and 2 have never been tested before, but are supported by my research on naturally occurring seedlings of Abies balsamea along a light availability gradient in northern hardwood forests. Three of the four most abundant morphotypes of ECMF have distinct distributions along a light-availability gradient with the two most abundant morphotypes switching dominance along the gradient. As predicted, each of the two dominant morphotypes was dominant in the portion of the light gradient where it had a positive effect on A. balsamea growth.

KEY WORDS: Growth of Abies balsamea seedlings, Composition of ectomycorrhizal fungi, Selective associations, Light intensity