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Contrasting patterns of historical colonization in white oaks (Quercus spp.) in California and Europe

Authors

  • DELPHINE GRIVET,

    1. Department of Ecology and Evolutionary Biology and Institute of the Environment, University of California, Box 951606, Los Angeles, CA 90095-1606, USA,
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  • MARIE-FRANCE DEGUILLOUX,

    1. Laboratory of Past Population Anthropology, University of Bordeaux I, avenue des Facultés, 33405 Talence, France,
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  • REMY J. PETIT,

    1. UMR Biodiversity, Genes & Ecosystems, Institut National de la Recherche Agronomique, 69 route d’Arcachon, F-33612 Cestas cedex, France
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  • VICTORIA L. SORK

    1. Department of Ecology and Evolutionary Biology and Institute of the Environment, University of California, Box 951606, Los Angeles, CA 90095-1606, USA,
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Victoria L. Sork, Fax: 3102060484; E-mail: vlsork@ucla.edu

Abstract

Phylogeography allows the inference of evolutionary processes that have shaped the current distribution of genealogical lineages across a landscape. In this perspective, comparative phylogeographical analyses are useful in detecting common historical patterns by either comparing different species within the same area within a continent or by comparing similar species in different areas. Here, we analyse one taxon (the white oak, genus Quercus, subgenus Quercus, section Quercus) that is widespread worldwide, and we evaluate its phylogeographical pattern on two different continents: western North America and Western Europe. The goals of the present study are: (i) to compare the chloroplast genetic diversity found in one California oak species vs. that found in the extensively studied European oak species (in France and the Iberian Peninsula); (ii) to contrast the geographical structure of haplotypes between these two taxa and test for a phylogeographical structure for the California species. For this purpose, we used the same six maternally inherited chloroplast microsatellite markers and a similar sampling strategy. The haplotype diversity within site as well as the differentiation among sites was alike in both taxa, but the Californian species has higher allelic richness with a greater number of haplotypes (39 vs. 11 in the European white oak complex). Furthermore, in California these 39 haplotypes are distributed locally in patches while in the European oaks haplotypes are distributed into lineages partitioned longitudinally. These contrasted patterns could indicate that gene movement in California oak populations have been more stable in response to past climatic and geological events, in contrast to their European counterparts.

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