~ Proceedings ~


Maxine Watson1, Kristin Scott1, Jon Griffith1, Stephanie Dieter12, Cynthia S. Jones2, Sunita Nanda1

The developmental ecology of mycorrhizal associations in mayapple, Podophyllum peltatum, Berberidaceae

1Department of Biology, Indiana University, Blooomington, Indiana 47405, USA. 2Department of Ecology and Evolutionary Biology, University of Connecticut, USA

Abstract. Associations between plants and arbuscular mycorrhizal (AM) fungi are widespread and well studied. Yet little is known about the pattern of association between clonal plants and AM fungi. Here we report on the pattern of mycorrhizal association within the rhizome systems of mayapple, Podophyllum peltatum. Mayapple is a long-lived understory clonal herb that is classified as obligately mycorrhizal. We found that while all mayapple rhizome systems maintained mycorrhizal associations, the percent colonization of roots by AM fungi differed among ramets of different age. The highest concentrations of AM fungi were in the roots of intermediate-aged ramets, while roots beneath the youngest ramet were not colonized. This pattern of ramet age or position-dependent colonization was observed in two separate studies; each conducted in a different year and at a different site. The pattern of AM fungal colonization of mayapple rhizome systems suggests that the mycorrhizal relationship is facultative at the ramet level. This conclusion is reinforced by our observation that augmentation of soil phosphate lowers root colonization by AM fungi. We also found that soil phosphate concentrations were depleted by ca. 1% under the same ramet positions where roots bore the highest AM fungal loads. Three nonexclusive hypotheses are proposed regarding the mechanisms that might cause this developmentally dependent pattern of mycorrhizal association.

Keywords

AM mycorrhizal associations, developmental ecology, developmental phenology, facultative symbiosis, Podophyllum peltatum, roots

Evolutionary Ecology (2001) 15: 4-6 (in press).