Investigating the Mycorrhizal Associates of the Myco-heterotroph Monotropsis odorata (Ericaceae) in Western North Carolina.
Committee: JJ Apodaca, Alisa Hove, Mark Brenner
The myco-heterotrophic plant Monotropsis odorata (pygmy pipes), by definition, relies on linkage to an existing mycorrhizal relationship for the supply of nutrients and sugars. This is a three-part association between M. odorata, a fungus, and a photosynthetic host plant. The fungal associates of most species of non-photosynthetic members of the Ericaceae (most members of the Monotropoideae) are known; however, there has been limited sampling for the fungi associated with M. odorata. In order to improve conservation efforts for this rare plant, it is essential to understand its ecology and identify the fungal associates. This investigation was conducted by isolating the internal transcribed spacer (ITS) gene region of fungal DNA from M. odorata root tips. Using a phylogenetic tree that visualizes the relationships between organisms, fungal isolates were grouped as Ascomycetes into the different families, Hyaloscyphaceae and Myxotrichaceae. This is the first report of a monotropoid plant forming associations with Ascomycete fungi. It is known that Ascomycetes form symbioses of an ericoid mycorrhizal type with other ericaceous plants, while monotropoid plants associate with Basidiomyetes. Additionally, M. odorata forms root systems similar to those of ericoid mycorrhizal plants and commonly shares their habitat. This points to an ericoid mycorrhizal habit of M. odorata which sets the species apart from other members of the Monotropoideae. Such evidence, strengthened by the molecular evidence of this study, supports the hypothesis for a polyphyletic Monotropoideae with the convergent evolution of myco-heterotrophy by M. odorata from within the subfamily Vaccinoideae. Based on this evidence and a previous study, Monotropsis odorata also differs from the fungal specificity observed in members of the Monotropoideae and seems to form associations with both Ascomycetes and Basidiomycetes.