Wesleyan University, Middletown, CT

Ecology and Specificity of a Local Orchid-Fungal Association

All orchids rely on symbiotic associations with fungi (mycorrhizas) to obtain carbon and soil nutrients.  A 16-week project carried out in the Plant Ecology Lab at the Smithsonian Environmental Research Center (SERC) investigated the degree of temporal and spatial variation that exists within the mycorrhizal relationship between Goodyera pubescens, a terrestrial orchid native to SERC property, and its fungal symbionts.  An experiment conducted in the laboratory showed that orchids are able to switch their symbionts when exposed to a new fungus, although the process of switching appears to be an extremely difficult one, significantly impeding the growth of the orchid.  A study of the populations on SERC property found that plants that were closer together were more likely to associate with genetically similar fungi.  In addition, all roots from a single plant and all ramets from a single clone appeared to associate with genetically identical fungi.

The plants in the populations of G. pubescens at SERC appear to associate with a wide range of fungi relative to some of the other local terrestrial orchid species, and there seems to be a relatively large degree of spatial and temporal variation in their mycorrhizal relationships.  Conducting similar studies on other orchids could help identify which species are particularly dependent on one very specific type of fungus.  These species would be the most susceptible to slight changes in fungal communities resulting from climate change and habitat destruction.  Thus, they would be good candidates to be targeted for conservation.