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Patterns and Mechanisms of Evolution of Island Plants

Motley, Timothy J. [1].

Biogeography and Phylogenetic Relationships of the Pacific Genera Labordia and Geniostoma (Loganiaceae).

Labordia is a Hawaiian endemic genus and Geniostoma is distributed throughout the other islands of the Pacific and Indian Oceans. These two sister genera are most closely related to the genus Logania, most species of which occur in Australia. The question exists as to whether Labordia and Geniostoma should be treated as a single genus or as two separate genera. These genera are separated primarily by the terminal inflorescences in the former genus and axillary inflorescences in the latter. The reason this debate has remained unsettled is the presence of Geniostoma rapense with terminal inflorescences located on the isolated island of Rapa iti. This species has been suspected to be the "missing link" necessary for understanding the generic relationships. Recent field research on Rapa has provided material for this study. Preliminary results from phylogenetic analyses suggest that Labordia and Geniostoma should be treated as distinct genera and that dioecy has evolved several times in the lineage. Furthermore the genus Logania is not monophyletic and may not have its origin in Australia where the genus is most species-rich. Additionally, in order to gain better phylogenetic resolution among the quickly evolving species of Labordia AFLP fingerprinting markers have been used in association with sequence data. These markers are congruent with the sequence data and in a combined analysis provide more resolution and biogeographic signal in the Hawaiian radiation.

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1 - New York Botanical Garden, Cullman Program for Molecular Systematics Studies, 200th Street and Kazimiroff Boulevard, Bronx, New York, 10458, USA

Island Biogeography

Presentation Type: Symposium or Colloquium Presentation
Session: 42-4
Location: Salon J - Austin Grand Ballroom/Hilton
Date: Wednesday, August 17th, 2005
Time: 9:15 AM
Abstract ID:234

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