Developmental and Structural Section
Wilson, C. , Calvin, C. .
Origin of Aerial Parasitism in the Loranthaceae.
THE large mistletoe family, Loranthaceae, contains 75 genera and approximately 1000 species. The family originated in the Southern Hemisphere and dispersed, apparently early, between fragments of Gondwana. It is now widely distributed on land surfaces of the former supercontinent. The Loranthaceae has three terrestrial, root-parasitic genera—a habit considered ancestral—and 72 genera of aerial, branch parasites. For almost two centuries, the origin of the mistletoe habit has been of interest to biologists. Two main evolutionary pathways have been proposed to explain the transition from terrestrial to aerial parasitism in the family. One theorizes the presence of an intermediate climbing ancestor in the path to the aerial habit. The other proposes a direct transfer from terrestrial to epiphytic growth following the germination of seeds on tree branches. We present molecular and morphological evidence that aerial parasitism has originated multiple times in the family, and that the origin of aerial parasitism in one Old World clade resulted from the direct transfer from terrestrial to epiphytic growth following the germination of seeds on tree branches. Our results argue against the currently preferred hypothesis that aerial Santalales necessarily evolved from climbing ancestors.
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1 - Rancho Santa Ana Botanic Garden, 1500 N. College, Claremont, California, 91711, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 312/Bell Memorial Union
Date: Monday, July 31st, 2006
Time: 1:15 PM