Barrett, Craig F. , Freudenstein, John .
Rangewide Phylogeography of the mycoheterotrophic Corallorhiza striata Complex (Orchidaceae: Epidendroideae).
The Striped Coralroot (Corallorhiza striata Lindley) is a rootless, reduced-leaved, fungus-eating orchid that shows extensive morphological variation across its North American range from Mexico to Canada. Relationships within this species complex are poorly understood. Three varieties were previously identified using morphometry: var. striata has the largest flowers (northern USA, southern Canada), var. vreelandii has intermediate-sized flowers (US and Mexican Cordilleras), and var. involuta has minuscule flowers (southern Mexico). Furthermore, the recently described C. bentleyi (endangered: Virginia and West Virginia, USA) shows strong morphological affinity to the C. striata complex. However, no DNA-based studies have been applied within this group. We sequenced both the Internal Transcribed Spacer (ITS) and the plastid rbcL gene for 1-6 individuals each from several populations spanning the entire geographic range of C. striata, including individuals from each of the three morphological varieties. We used Maximum Parsimony, Bayesian, Nested Clade, and Coalescent Analyses to address several questions regarding the phylogeography of C. striata. ITS and rbcL gene trees were concordant, although rbcL had higher resolution and support values. The combined ITS + rbcL tree showed increased support and resolution, with several clades specific to geographic regions. These included a Californian clade and a Mexican/ Rocky Mountain clade (both roughly corresponding to vars. vreelandii and involuta), and a "northern" clade (var. striata) nested within the latter. Sister to this collective clade was C. bentleyi + C. striata var. involuta (a single accession from Oaxaca, Mexico), representing the deepest divergence in the C. striata complex. Thus, there are two distinct lineages in the group, each occurring in both Mexico and the USA/ Canada. These results suggest a Mexican origin and northeastern expansion/ diversification of both lineages. They also illustrate the need for further taxonomic treatment; especially concerning collections of var. involuta, which fall in multiple clades in this analysis.
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1 - Ohio State University, Department of Evolution, Ecology, and Organismal Biology, OSU Herbarium (OS), Museum of Biological Diversity, 1315 Kinnear Rd., Columbus, Ohio, 43212, USA
2 - Ohio State University, Department of Evolution, Ecology and Organismal Biology, Museum of Biological Diversity, 1315 Kinnear Rd., Columbus, Ohio, 43212, USA
nest clade analysis
Presentation Type: Oral Paper:Papers for Topics
Location: Lake Michigan/Hilton
Date: Tuesday, July 10th, 2007
Time: 1:00 PM