Systematics Section / ASPT
Rothacker, Erik Paul , Freudenstein, John .
A phylogeny of the basal Epidendroideae (Orchidaceae) using total evidence from molecules and morphology.
Considering the significance of the basal Epidendroideae in understanding patterns of morphological evolution within the subfamily, it is surprising that no fully resolved hypothesis of historical relationships has been presented for these orchids. This is the first significant study to improve both taxon and character sampling. An hypothesis of relationships is presented based on the results of a total evidence combined analysis using 3 molecular loci, gap characters and morphology. These results place Palmorchis at the base of the tree, sister to Neottieae, followed successively by Triphoreae sister to Epipogium then Sobralieae. Tropidieae form a clade with the advanced Epidendroideae sister to a grade of Nervilieae and Gastrodieae. Diceratostele gabonensis is found to unite within this grade. These results support a primitive condition of plicate leaves with absent or reduced leaves evolving minimum of 5 times. An objective of this study was to investigate anther evolution. Anther position is important for pollination. Among the basal members we find anthers that are erect, or exhibit varying degrees of incumbency. It is clear from these results that the erect anthers of some orchids evolved independently from those observed in the Orchidoid, and the primitive condition among the basal Epidendroideae is suberect/subincumbent. Epidendroid incumbency is achieved via combinations of bending in different regions of the anther, with the primitive condition bending in the column region and to a lesser extent, the basal region of the anther. The primitive condition for pollinia is free monads with tetrads evolving twice, sectile pollinia have evolved 4 times. Some authors have suggested that the type III stigma of Cephalanthera, possessing mostly primitive features, was evidence that it was intermediate between Neottieae and advanced Epidendroideae; given its position in this analysis, this is a case of convergence.
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1 - Ohio State University, Department of Evolution, Ecology and Organismal Biology, Museum of Biological Diversity, 1315 Kinnear Rd., Columbus, Ohio, 43212, USA
2 - Ohio State University, Department of Evolution, Ecology, and Organismal Biology, University Herbarium, 1315 Kinnear Rd., Columbus, Ohio, 43212, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Continental A/Hilton
Date: Tuesday, July 10th, 2007
Time: 11:15 AM