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NEW PUBLICATIONS!!

Freudenstein JV & Senyo DM. 2008. Relationships and evolution of matK in a group of leafless orchids (Corallorhiza and Corallorhizinae; Orchidaceae: Epidendroideae). American Journal of Botany 95(4): 498–505.

Barrett CF & Freudenstein JV. 2008. Molecular evolution of rbcL in the mycoheterotrophic coralroot
orchids (Corallorhiza Gagnebin, Orchidaceae). Molecular Phylogenetics and Evolution 47: 665–679

NSF 0415920 - Relationships among gene lineages, morphology, geography and fungal associations in Corallorhizinae (Orchidaceae).

John V. Freudenstein, PI, Ohio State University, Columbus, OH

D. Lee Taylor, Co-PI, University of Alaska - Fairbanks, AK

Orchidaceae are the largest family of angiosperms and exhibit amazing diversity in floral and vegetative specializations. Many of these features are well known, but less so are the fungal associations that all orchids have, at least as seedlings. Given that the fungi have not been shown to derive a benefit from this relationship, it constitutes an unusual host-parasite association, with the orchid being the parasite. Some orchids are completely dependent on the fungi for energy, having lost leaves and the ability to photosynthesize. Corallorhiza is a prime example, comprising 11 species of temperate-montane terrestrials. This genus provides a special opportunity to gain an understanding of the relationships among orchid morphology, geographical distribution, and fungal associations because at least one species (C. trifida) is still partly photosynthetic, meaning that Corallorhiza occupies an intermediate position on the path to heterotrophy, providing a window into this transition. Corallorhiza, together with the leafy genera Aplectrum, Cremastra and Oreorchis, forms a monophyletic unit within Corallorhizinae. One objective is to construct a robust pattern of relationships for these genera, thereby testing their monophyly and providing a context for examining the shifts in fungal utilization that occurred between the leafy species and Corallorhiza. Another principal objective is to reconstruct patterns of relationship within and among species of Corallorhiza across North America using plastid and nuclear DNA sequences. Patterns of relationship among the fungal associates of the orchids will also be reconstructed. These trees will then be used to analyze correlations among orchid population history, fungal associate, geography and orchid morphology. This analysis will address questions including to what degree the orchid-fungal association is one of phylogenetic tracking (specificity) vs. opportunism, whether shifts in fungal utilization are correlated with shifts in orchid morphology and/or geography, and whether the pattern observed in some Corallorhiza species of basal Mexican lineages of orchids with more northern populations being nested among them is a general one for the genus (and therefore perhaps for other taxa with similar distribution). The project incorporates carefully planned fieldwork to obtain both orchid and fungal samples, and brings together the expertise of the PIs in their respective areas of the project to facilitate a comprehensive analysis that would not otherwise be possible, yielding perhaps the most detailed and multifaceted analysis of a species association system to date. It is only in the context of such a comprehensive hierarchic analysis such as this that we can begin to understand the changes that have occurred in organismal associations through space and time.

This project has broader impacts for science and beyond in a number of ways. It provides a case study of a synthesis of modern approaches to a detailed analysis of angiosperm-fungal associations, plant morphology, gene lineages and geography. As such it can be a model for future work. It enhances the infrastructure of science by bringing new collections of these taxa into museums where they have broad accessibility and the DNA sequences generated into public database where they will be broadly available. The project lays the foundation for future evolutionary work on this multifaceted system, preparing the way for future study of plastid DNA evolution and of the relationship of fungal associations to angiosperm speciation. The interactions with scientists in China, Korea and Mexico will result in strengthened networks of cooperation. The project brings together research and education by integrating graduate and undergraduate students in the project. It further enhances the integration of research and teaching by utilization of the results of the project as a case study in the PIs’ teaching in courses on systematics, microbial diversity and symbiosis, and in their outreach to the public at large. This includes ongoing consultation with forest service botanists on land use planning, as well as presentations to various groups. Increased understanding of orchid-fungus relationships has direct conservation benefits, since the fungal partners are required for orchid germination and growth. Programs that attempt to maintain or reintroduce endangered species of orchids must address the issue of fungal partner availability and identity.