Collaborative Research: Relationships Among Gene Lineages, Morphology, Geography and Fungal Associations in Corallorhizinae (Orchidaceae)

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0416378Taylor Orchids comprise the largest family of flowering plants and are extremely diverse. All are parasitic on fungi at least when seeds germinate, but little is known about this relationship. Some orchids depend on fungi for all nutrition because they are non-photosynthetic. Orchids of the genus Corallorhiza are prime examples, comprising 11 species of mainly North American temperate-montane terrestrials. This group provides a special opportunity to study the changes that happen when plants give up photosynthesis, because at least one species is photosynthetic while others are not. Such changes include partial loss of chloroplast DNA, structural modifications of the plant, and shifts among the groups of their associated fungi. Reconstructing phylogenetic relationships among populations of the species of Corallorhiza and their fungi through analysis of DNA sequences will reveal to what extent the orchid-fungal association is essentially random vs. targeted to certain fungal groups; adding orchid morphology and locality data will show whether shifts in fungal utilization are at all correlated with these factors. Because of the intensive sampling, any repeated correlations of present-day distribution with lineage histories will be shown, which might reflect post-glacial migration. This will provide a better understanding of how current plant distributions in North America came to be. The project incorporates carefully planned fieldwork to obtain both orchid and fungal samples, and brings together the expertise of orchid specialist John Freudenstein at Ohio State University and fungal specialist Donald Taylor at University of Alaska to facilitate a comprehensive analysis that would not otherwise be possible, yielding perhaps the most detailed and multifaceted analysis of a plant-microbe interaction to date.This project has broad impact for science and beyond in a number of ways. It provides a synthesis of modern approaches to a detailed analysis of flowering plant-fungal associations, plant morphology, gene lineages and geography. As such, it may serve as a model for future work on similar systems. 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 databases where they will be available to all. 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 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 identity and availability.