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Patterns and Mechanisms of Evolution of Island Plants

Friar, Elizabeth [1], Prince, Linda [1], Cruse-Sanders, Jennifer [1], McGlaughlin, Mitchell [1], Roalson, Eric [2].

Ecological Speciation in Maui-Endemic Dubautias (Asteraceae).

The ecological theory of adaptive radiation postulates that divergent natural selection drives rapid speciation and phenotypic diversification, overriding the conservative process of gene flow among populations. The process of species diversification can thus be viewed as a balance between differential natural selection and gene flow. The Hawaiian silversword alliance is a premier example of adaptive radiation in plants. One recently evolved example of a monophyletic single-island species radiation into a small species flock is the East Maui endemic Dubautias: D. menziesii, D. platyphylla, D. reticulata, and D. waianapanapaensis. If the speciation event giving rise to this group of species does not predate their habitat, the maximal date of divergence is the age of Haleakala volcano, or about 0.75 million years. Despite their close genetic relationships, these species are morphologically and ecologically distinct. These four species, therefore, represent a recent ecological diversification into different niches, apparently based upon fine-level partitioning of moisture habitats. They are capable of interbreeding where they come into contact, but typically inhabit different, parapatric habitats and maintain their morphological distinctness. Here, we examine the ecological, morphological, and genetic differentiation within and among populations of the East Maui endemic species of Dubautia section Railliardia using ecological, morphometric, microsatellite, and DNA sequence data. We found that these species show significant ecological and morphological differentiation, with the primary axes separating the taxa into "wet" and "dry" habitat groupings. Microsatellite data show significant differentiation among species, very little gene flow, and variable amounts of diversity within species with most of the differentiation occurring along ecological lines. DNA sequence data of several single-copy nuclear loci show differing levels of lineage sorting among loci. The interplay of genetic, ecological, and geographical forces shaping species differentiation in this group will be discussed.


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1 - Rancho Santa Ana Botanical Garden, 1500 North College Avenue, Claremont, California, 91711, USA
2 - Washington State University, School of Biological Sciences, Po Box 644236, Pullman, Washington, 99164-4236, USA

Keywords:
speciation
silversword
Adaptive radiation.

Presentation Type: Symposium or Colloquium Presentation
Session: 42-7
Location: Salon J - Austin Grand Ballroom/Hilton
Date: Wednesday, August 17th, 2005
Time: 11:15 AM
Abstract ID:323


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