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Phylogeny and Evolution of Mycorrhizal Associations in the Myco-heterotrophic Hexalectris Raf. (Orchidaceae : Epidendroideae)

Kennedy, Aaron H.
http://rave.ohiolink.edu/etdc/view?acc_num=miami1232724178

Abstract Details

2009, Doctor of Philosophy, Miami University, Botany.
Some plant species have abandoned an autotrophic life style and obtain their carbon and mineral nutrition exclusively from mycorrhizal fungi. Although myco-heterotrophic species have evolved in many plant families, they are most common in the Orchidaceae. Several myco-heterotrophic orchid species have been shown to associate with a very narrow range of ectomycorrhizal forming fungi, revealing a high degree of mycorrhizal specificity. However, these studies have often investigated single or few, often unrelated, species without support for their monophyly or knowledge of their phylogenetic relationships. Using primarily molecular methods and phylogenetic analyses, this dissertation investigates i) the monophyly and circumscription of Hexalectris species, ii) interspecific phylogenetic relationships within Hexalectris, iii) the identities of the mycorrhizal fungi that associate with each Hexalectris species, iv) the breadth of mycorrhizal associations within Hexalectris and within each of its species, and v) uses a Hexalectris phylogeny as a framework for investigating mycorrhizal specificity and patterns of associations. The monophyly of H. warnockii, H. grandiflora, H. brevicaulis, and H. nitida, plus the H. spicata species complex, are well supported. The remaining species are not monophyletic, prompting the recircumscription of H. spicata s.l. as H. spicata and H. arizonica, H. revoluta s.l. as H. revoluta and H. colemanii, and H. fallax as a synonym of H. parviflora. Extreme specificity with ectomycorrhizal agaricomycete fungi was identified in each Hexalectris species. Hexalectris warnockii associates exclusively with members of the Thelephoraceae; H. brevicaulis and H. grandiflora associate exclusively with members of Russulaceae and Sebacinaceae subgroup A; the remaining species, all members of the H. spicata complex, associate strictly with members of Sebacinaceae subgroup A. Optimizing these associations onto a Hexalectris phylogeny reveals that, with one exception, each Hexalectris species associates with a different clade or group of fungal clades, and that shifts in association from one group of fungi to another occurred during each speciation event in the evolutionary history of this genus.
Dr. Linda E. Watson (Advisor)
Dr. Nicholas P. Money (Committee Member)
Dr. R. James Hickey (Committee Member)
Dr. D. Lee Taylor (Committee Member)
Dr. David J. Berg (Committee Member)
97 p.
Biology; Botany
Orchidaceae; orchid; Hexalectris; phylogenetics; molecular systematics; mycorrhizae; myco-heterotrophy; mycoheterotrophy; ITS; plastid; specificity; tripartite; ectomycorrhizae

Recommended Citations

Citations

  • Kennedy, A. H. (2009). Phylogeny and Evolution of Mycorrhizal Associations in the Myco-heterotrophic Hexalectris Raf. (Orchidaceae : Epidendroideae) [Doctoral dissertation, Miami University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=miami1232724178

    APA Style (7th edition)

  • Kennedy, Aaron. Phylogeny and Evolution of Mycorrhizal Associations in the Myco-heterotrophic Hexalectris Raf. (Orchidaceae : Epidendroideae). 2009. Miami University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=miami1232724178.

    MLA Style (8th edition)

  • Kennedy, Aaron. "Phylogeny and Evolution of Mycorrhizal Associations in the Myco-heterotrophic Hexalectris Raf. (Orchidaceae : Epidendroideae)." Doctoral dissertation, Miami University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=miami1232724178

    Chicago Manual of Style (17th edition)

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This open access ETD is published by Miami University and OhioLINK.