Givnish, Thomas J. , Millam, Kendra J. , Mast, Austin , Patterson, Thomas B. , Theim, Terra J. , Hipp, Andrew , Henss, Jillian M. , Smith, James F. , Woods, Kenneth , Sytsma, Kenneth J. .
Origin, adaptive radiation, and diversification of the Hawaiian lobeliads (Campanulaceae).
THE Hawaiian lobeliads (6 genera, ca. 125 spp.) have long been viewed as one of the most spectacular examples of adaptive radiation in plants. They are the largest family of Hawaiian plants, comprising one-eighth of the native flora of the most isolated archipelago on earth. The origins of this group have been hotly debated, with morphological data suggesting three to five independent colonizations, even though Hawaii is more than 3600 km from the nearest continent and most other tall islands in the central Pacific lack woody lobeliads entirely. Here we present a new molecular phylogeny based on DNA sequences from six rapidly evolving chloroplast regions, showing that the Hawaiian lobeliads are the product of a single immigration event; that their ancestor arrived from Asia or elsewhere in the Pacific roughly 13 My ago; and that this ancestor was most likely woody, wind-dispersed, bird-pollinated, and adapted to open habitats at mid-elevations. Invasion of closed tropical forests spurred the evolution of fleshy fruits; the limited dispersal of such fruits in wet-forest understories appears to have accelerated speciation and led to a series of parallel adaptive radiations in the largest genus Cyanea, with most species restricted to single islands. The consistency of species number in Cyanea across all tall islands except Hawai`i suggests that its ecological diversification saturates in less than 1.3 million years. The high diversity of the Hawaiian lobeliads thus appears to reflect a hierarchical adaptive radiation in habitat, then elevation and flower-tube length, and provides important insights into the pattern and tempo of diversification in a tropical, species-rich clade of vascular plants.
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1 - University of Wisconsin Madison, Department of Botany, Birge Hall, 430 Lincoln Drive, Madison, Wisconsin, 53706-1381, USA
2 - Florida State University, Department of Biological Sciences, Tallahasse, Florida, 32306-1100, USA
3 - 1969 Loring Ave., San Diego, California, 92109-1406
4 - Morton Arboretum, Lisle, Illinois, 60532-1293, USA
5 - Boise State University, Department of Biology, 1910 University Drive, Boise, Idaho, 83725-1515, USA
6 - Pelea, Kalaheo, Hawaii, 96741, USA
Presentation Type: Oral Paper:Papers for Topics
Location: 134/Performing Arts Center
Date: Wednesday, August 2nd, 2006
Time: 11:15 AM