Detecting genetic structure in migrating bowhead whales off the coast of Barrow, Alaska

Authors

  • P. E. JORDE,

    1. Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, PO Box 1066 Blindern, N-0316 Oslo, Norway,
    2. Institute of Marine Research, Flødevigen, N-4817 His, Norway,
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  • T. SCHWEDER,

    1. Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, PO Box 1066 Blindern, N-0316 Oslo, Norway,
    2. Department of Economics, University of Oslo, PO Box 1095 Blindern, N-0317 Oslo, Norway,
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  • J. W. BICKHAM,

    1. Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, TX 77843-2258, USA,
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    • Present address: Center for the Environment and Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907, USA.

  • G. H. GIVENS,

    1. Department of Statistics, 1877 Campus Delivery, Colorado State University, Fort Collins, CO 80523, USA,
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  • R. SUYDAM,

    1. North Slope Borough, Department of Wildlife Management, PO BOX 69 Barrow, AK 99723, USA
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  • D. HUNTER,

    1. Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, TX 77843-2258, USA,
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  • N. C. STENSETH

    1. Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, PO Box 1066 Blindern, N-0316 Oslo, Norway,
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Per Erik Jorde, Institute of Marine Research, Nye Flødevigveien 20, N-4817 His, Norway. Fax: +47 37 05 90 01; E-mail: p.e.jorde@bio.uio.no

Abstract

We develop a general framework for analysing and testing genetic structure within a migratory assemblage that is based on measures of genetic differences between individuals. We demonstrate this method using microsatellite DNA data from the Bering-Chukchi-Beaufort stock of bowhead whales (Balaena mysticetus), sampled via Inuit hunting during the spring and autumn migration off Barrow, Alaska. This study includes a number of covariates such as whale ages and the time separation between captures. Applying the method to a sample of 117 bowhead whales, we use permutation methods to test for temporal trends in genetic differences that can be ascribed to age-related effects or to timing of catches during the seasons. The results reveal a pattern with elevated genetic differences among whales caught about a week apart, and are statistically significant for the autumn migration. In contrast, we find no effects of time of birth or age-difference on genetic differences. We discuss possible explanations for the results, including population substructuring, demographic consequences of historical overexploitation, and social structuring during migration.

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