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First published online April 13, 2009; doi:10.3732/ajb.0800243 American Journal of Botany 96: 958-967 (2009) © 2009 Botanical Society of America, Inc.

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Phylogeographic patterns and demographic history of Schiedea globosa (Caryophyllaceae) on the Hawaiian Islands¹

² Department of Biological Sciences, Mississippi State University, Mississippi State, Mississippi 39762 USA ³ Department of Ecology and Evolutionary Biology, University of California, Irvine, California 92697 USA ⁴ Department of Botany, MRC 166, P.O. Box 37012, Smithsonian Institution, Washington, D.C. 20013-7012 USA ⁵ Department of Biology, University of South Dakota, Vermillion, South Dakota 57069 USA

ABSTRACT

Geomorphological changes have been demonstrated to have had profound impacts on biodiversity, often leading to demographic expansions and contractions and allopatric divergence of taxa. We examined DNA sequence variation at two nuclear and one maternally inherited plastid locus among 10 populations of Schiedea globosa on the Hawaiian Islands to assess the primary factors shaping genetic structure, phylogeographic patterns, and the importance of geographic isolation to population divergence. Schiedea globosa has characteristics that may promote gene flow, including wind pollination and rafting of plants in ocean currents. However, we detected significant differentiation among populations on all islands except Hawaii, with the maternally inherited plastid locus having the greatest genetic structure (F_ST = 0.81). Migration rates across all loci are less than one migrant per generation. We found evidence of growth in several populations and on the islands of Molokai and Maui, which supports population expansion associated with the formation of Maui Nui during the last glacial maximum. Similar to data for many other Hawaiian taxa, these data suggest S. globosa originated on Oahu and subsequently colonized Molokai, Maui, and Hawaii in progression. Given the high level of genetic structure, allopatric divergence will likely contribute to further divergence of populations.

Key Words: ancestral polymorphism • Caryophyllaceae • gene coalescence • DNA sequence • intraspecific variation • migration • phylogeography • Schiedea globosa

Received for publication 15 July 2008. Accepted for publication 14 January 2009.

FOOTNOTES

¹ The authors thank S. Perlman, K. Wood, B. Garnett, and K. Kawela for collection of plant material, Maui Land and Pineapple for access to land, and two anonymous reviewers for comments that improved the manuscript. This work was funded by grant DEB-0445410 from the National Science Foundation.

⁶ Corresponding author (e-mail: Lisawallace{at}biology.msstate.edu)

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