Systematics Section / ASPT
Kennedy, Aaron H. , Watson, Linda E. .
Phylogenetic relationships and patterns of mycorrhizal association within the myco-heterotrophic genus Hexalectris Raf. (Orchidaceae).
HEXALECTRIS Raf. is a small genus of non-photosynthetic, myco-heterotrophic, terrestrial orchids which exhibits a fascinating life-history. Underground, these plants maintain long-lived rhizomes that may reach many feet long. These rhizomes have highly reduced roots along their length that are the site for mycorrhizal colonization. These fungi simultaneously form ectomycorrhizae with nearby trees from where they obtain carbon, some of which is extracted from the mycorrhizae by the orchid. Aboveground, these terrestrial plants have short-lived, erect, leafless stems. Its seven species are morphologically variable in terms of stem height and color; flower number and color, lateral sepal and petal shape, anther color, and number of lamellae. The center of diversity for Hexalectris is the mountainous region of southern Texas and northern Mexico. The most widespread taxon, H. spicata var. spicata, ranges from northern Mexico, throughout much of the Midwest and southeastern U.S. Phylogenetic relationships among Hexalectris taxa remain unclear, particularly among members of the H. spicata complex (H. spicata, H. nitida, H. revoluta, and H. parviflora) that exhibit similar floral morphologies. Phylogenetic analyses of chloroplast DNA sequences support the monophyly of Hexalectris, and support traditional taxonomic circumscriptions of H. warnockii, H. grandiflora, H. brevicaulis, and the H. spicata complex. Additionally, we are using molecular approaches combined with phylogenetic analyses to identify lineages of mycorrhizae associated with Hexalectris. We are using the Hexalectris phylogeny as a framework for understanding patterns of mycorrhizal relationships. Preliminary results from fungal ITS sequences indicate that each of four Hexalectris lineages specifically associate with members of different and distantly related families of Basidiomycota: H. warnockii with Thelophoraceae, H. grandiflora with Ceratobasidiaceae, H. brevicaulis with Russulaceae, and the H. spicata complex with Sebacinaceae.
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1 - Miami University, Department of Botany, Oxford, Ohio, 45056, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 144/Performing Arts Center
Date: Tuesday, August 1st, 2006
Time: 2:00 PM