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Abstract Detail

Systematics/Phytogeography / Taxonomie/ Section

Mathews, Sarah [1], Schneeweiss, Gerald M. [2], Yatskievych, George [3].

Phylogenetic affinities of a new holoparasitic genus of Orobanchaceae endemic to Guerrero, Mexico, inferred from molecular data.

We have tested the familial placement of a new genus being described from the Sierra Madre del Sur in Guerrero, Mexico, which parasitizes large lateral roots of mature trees of Hedyosmum mexicanum (Chloranthaceae). A number of morphological features suggest affinity with the Orobanchaceae, including: 1) the parasitic habit; 2) production of 4 stamens with loosely connivent anthers; 3) parietal placentation; 4) a hollow style terminating in a discoid-crateriform stigma with a central pore; 5) seeds with a prominent, loose, reticulate outer testa in which the enlarged cells rupture into concave, polygonal facets. However, several autapomorphies would require expansion of the morphological circumscription of the family. Our molecular studies confirm that the new taxon is a previously undescribed, holoparasitic member of the Orobanchaceae. Data from ITS and rps2 suggest that it belongs to a clade including Boschniakia, Conopholis, and Epifagus, but currently are not definitive regarding its placement among these genera. Data from phytochromes A and B provide strong evidence of a clade of holoparasitic genera that includes Boschniakia/Kopsiopsis, Conopholis, and Epifagus, as well as Orobanche sensu lato, Cistanche, and Mannagettaea. Within the holoparasitic clade, the phytochrome data strongly support the clade of Boschniakia/Kopsiopsis, Conopholis, and Epifagus. Thus, we are further testing the placement of the new genus with additional data from phytochromes. However, the ITS and rps2 data suggest that, as with morphology, the genus is characterized by a large number of molecular autapomorphies.

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1 - Harvard University, Arnold Arboretum, Harvard University Herbaria, 22 Divinity Avenue, Cambridge, Massachusetts, 02138, USA
2 - University of Vienna, Department of Biogeography, Rennweg 14, Vienna, Vienna, A-1030, Austria
3 - Missouri Botanical Garden, Po Box 299, St Louis, Missouri, 63166-0299, USA

new genus
Hedyosmum mexicanum.

Presentation Type: Oral Paper:Papers for Sections
Session: 55
Location: 177/Law
Date: Wednesday, July 30th, 2008
Time: 9:15 AM
Number: 55006
Abstract ID:858

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