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Systematics, Phylogeography, Fungal Associations, and Photosynthesis Gene Evolution in the Fully Mycoheterotrophic Corallorhiza striata Species Complex (Orchidaceae: Epidendroideae)

Barrett, Craig F.
http://rave.ohiolink.edu/etdc/view?acc_num=osu1274732496

Abstract Details

2010, Doctor of Philosophy, Ohio State University, Evolution, Ecology and Organismal Biology.
Corallorhiza is a genus of obligately mycoheterotrophic (fungus-eating) orchids that presents a unique opportunity to study phylogeography, taxonomy, fungal host specificity, and photosynthesis gene evolution. The photosysnthesis gene rbcL was sequenced for nearly all members of the genus Corallorhiza; evidence for pseudogene formation was found in both the C. striata and C. maculata complexes, suggesting multiple independent transitions to complete heterotrophy. Corallorhiza may serve as an exemplary system in which to study the plastid genomic consequences of full mycoheterotrophy due to relaxed selection on photosynthetic apparatus. In an investigation of molecular and morphological variation in Corallorhiza striata—a species complex distributed from Mexico to Canada—four plastid DNA clades were identified, displaying statistically significant differences in floral morphology. The biogeography of the C. striata complex is more complicated than previously hypothesized, with two main lineages present in both Mexico and northern North America; this study adds to a growing body of data on organisms sharing this common distribution. To investigate fungal host specificity in the C. striata complex, we sequenced plastid DNA for orchids and nuclear DNA for fungi, and found four plastid clades that associate with divergent sets of ectomycorrhizal fungi; all within a single, variable species, Tomentella fuscocinerea. This is perhaps the most extensive investigation of specificity for any mycoheterotroph, and has conservation implications for these rare orchids. To address taxonomy, conservation, and phylogeography within the C. striata complex, I analyzed continuous floral characters, plastid DNA, and nuclear DNA for 155 individuals across North America. The main finding was that C. striata s.s., C. bentleyi, and C. involuta are separate species. Within the highly variable and widespread C. striata s.s., there are furthermore three evolutionarily distinct units, which are recognized at the level of variety. These findings carry further conservation implications for C. striata. The geographic pattern of genetic breaks in C. striata is similar to that in several co-distributed ectomycorrhizal tree species, suggesting that these species may have responded similarly to past geologic/climatic processes, but the timing of these events in C. striata remains to be addressed.
John Freudenstein, Ph.D (Advisor)
John Wenzel, PhD (Committee Member)
Andrea Wolfe, PhD (Committee Member)
224 p.
Biology; Botany; Ecology; Genetics; Geography
Orchid; mycoheterotrophy; fungi; photosynthesis; DNA; evolution; phylogenetics; species; phylogeography; parasitism; morphology

Recommended Citations

Citations

  • Barrett, C. F. (2010). Systematics, Phylogeography, Fungal Associations, and Photosynthesis Gene Evolution in the Fully Mycoheterotrophic Corallorhiza striata Species Complex (Orchidaceae: Epidendroideae) [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1274732496

    APA Style (7th edition)

  • Barrett, Craig. Systematics, Phylogeography, Fungal Associations, and Photosynthesis Gene Evolution in the Fully Mycoheterotrophic Corallorhiza striata Species Complex (Orchidaceae: Epidendroideae). 2010. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1274732496.

    MLA Style (8th edition)

  • Barrett, Craig. "Systematics, Phylogeography, Fungal Associations, and Photosynthesis Gene Evolution in the Fully Mycoheterotrophic Corallorhiza striata Species Complex (Orchidaceae: Epidendroideae)." Doctoral dissertation, Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1274732496

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.