Gemmill, Chrissen E.C. , Lowry, Porter P. II , Munzinger, Jérôme .
Explosive radiation of New Caledonian Pittosporum: exploring biogeography and evolutionary patterns.
New Caledonia is perhaps the most important hotspot for botanical diversity on Earth. It comprises a diverse array of habitat and ecosystem types including rain forests, maquis shrub lands, and sclerophyllous forests. This small archipelago consists of the main island Grande Terre (and several nearby, associated islands) and the outlying Loyalty Islands. About 74% of the ca. 3,250 plant species found in New Caledonia are endemic and the flora ranks 4th globally in number of endemic plant families. The diversity and endemism of the flora largely reflect the long and dynamic geological history and eco-geographic heterogeneity of this isolated Gondwanan fragment. Pittosporum (Pittosporaceae, the Pittosporum family), a genus present throughout the tropical and warm temperate regions of Australia, New Zealand, Africa and Madagascar, and archipelagos of the Pacific including the Hawaiian Islands, has undergone explosive radiation in New Caledonia, as evidenced by the large number of endemic taxa (ca. 50 species) currently recognized, although many are of uncertain taxonomic distinction. All species produce distinctive woody capsules that open to reveal dark seeds imbedded in a viscous resin. The distribution of Pittosporum over these vast distances and remote islands is thought to have resulted from long-distance trans-oceanic dispersal events via birds. We are using an integrated, holistic approach to study the evolution of New Caledonian Pittosporum, including DNA sequence variation, traditional taxonomy and morphological character analysis, and ecology. Based on molecular phylogenetic studies we hypothesize that Pittosporum reached New Caledonia through multiple colonization events from Australia, rendering the genus non-monophyletic within the archipelago. Each of the lineages resulting from a colonization event has subsequently radiated, generating several species-rich assemblages of closely related taxa. Furthermore, New Caledonia itself has served a springboard for multiple migrations into other Pacific archipelagos, including New Zealand.
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1 - University of Waikato, Centre of Biodiversity and Ecology Research (CBER), Private Bag 3105, Hamilton, 2001, New Zealand
2 - Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri, 63166
3 - Institut de Recherche pour le Developpement, Laboratoire de Botanique, bp A5, Noumea, 98848, New Caledonia
Presentation Type: Oral Paper:Papers for Topics
Date: Wednesday, July 30th, 2008
Time: 9:15 AM