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Reconstruction of caribou evolutionary history in Western North America and its implications for conservation

Authors

  • BYRON V. WECKWORTH,

    1. Faculty of Environmental Design, University of Calgary, Calgary, Alberta, Canada T2N 1N4
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  • MARCO MUSIANI,

    1. Faculty of Environmental Design, University of Calgary, Calgary, Alberta, Canada T2N 1N4
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  • ALLAN D. McDEVITT,

    1. Faculty of Environmental Design, University of Calgary, Calgary, Alberta, Canada T2N 1N4
    2. School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Ireland
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  • MARK HEBBLEWHITE,

    1. Wildlife Biology Program, Department of Ecosystem and Conservation Sciences, College of Forestry and Conservation, University of Montana, MT 59812, USA
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  • STEFANO MARIANI

    1. School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Ireland
    2. School of Environment and Life Sciences, University of Salford, Salford M5 4WT, UK
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Byron Weckworth, Fax: 403 284 4399; E-mail: byweck@gmail.com

Abstract

The role of Beringia as a refugium and route for trans-continental exchange of fauna during glacial cycles of the past 2 million years are well documented; less apparent is its contribution as a significant reservoir of genetic diversity. Using mitochondrial DNA sequences and 14 microsatellite loci, we investigate the phylogeographic history of caribou (Rangifer tarandus) in western North America. Patterns of genetic diversity reveal two distinct groups of caribou. Caribou classified as a Northern group, of Beringian origin, exhibited greater number and variability in mtDNA haplotypes compared to a Southern group originating from refugia south of glacial ice. Results indicate that subspecies R. t. granti of Alaska and R. t. groenlandicus of northern Canada do not constitute distinguishable units at mtDNA or microsatellites, belying their current status as separate subspecies. Additionally, the Northern Mountain ecotype of woodland caribou (presently R. t. caribou) has closer kinship to caribou classified as granti or groenlandicus. Comparisons of mtDNA and microsatellite data suggest that behavioural and ecological specialization is a more recently derived life history characteristic. Notably, microsatellite differentiation among Southern herds is significantly greater, most likely as a result of human-induced landscape fragmentation and genetic drift due to smaller population sizes. These results not only provide important insight into the evolutionary history of northern species such as caribou, but also are important indicators for managers evaluating conservation measures for this threatened species.

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