PARENT SESSION
Poster Session 23: Soil Ecology
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Successional changes in arbuscular mycorrhizal fungal communities may occur in the absence of host species variation.

Bentivenga, Stephen^*,, Badtke, Danica,

ABSTRACT- Arbuscular mycorrhizal fungal (AMF) communities have been shown to vary with successional stage in several ecosystems. Shifts in the AMF community are usually attributed to concomitant changes in the plant host community. However, certain ecosystems such as sand dunes do not display major shifts in plant communities as they age. We examined AMF communities in the successional stages of sand dune development on the shores of Lake Michigan at Point Beach State Forest, in Manitowoc County, Wisconsin. Rhizosphere soil from isolated plants of the dominant grass Ammophila breviligulata were collected from the embryo dune, the primary dune and secondary dune. Spores of AMF were extracted from rhizosphere soil, identified to species, and enumerated. Ten AMF species were found representing 4 genera. Total AMF spore number was approximately 5 times higher in the embryo dune than in the other dunes (F = 10.644, p < 0.001). The number of species per dune did not vary (mean = 4.08, F = 1.661, p = 0.20); however, the community composition differed significantly. Whereas some species were found evenly across the dunes (Glomus verruculosum), others such as Glomus clarum were found only in the embryo dune. Several species were relatively abundant in the embryo dune, but rare in the other dunes (e.g., Glomus etunicatum, Scutellospora calospora, and an undescribed Glomus sp.). Two species (Gigaspora margarita and Glomus constrictum) were absent in the embryo but present in the remaining dunes. Cluster analysis (Ward's method) and principal component analysis each indicated that the community composition of the embryo dune was distinct relative to the other dunes. To our knowledge, this is the first report of shifts in AMF species composition associated with a single plant species in a successional gradient. It is unclear as to which factors may be responsible for the differences in the community structure of the successional dune stages. Current studies are being performed to assess the AMF community at other dune sites to determine if this is a common phenomenon.

Key words: succession, arbuscular mycorrhizal fungi, Ammophila breviligulata, sand dune