Integrative use of spatial, genetic, and demographic analyses for investigating genetic connectivity between migratory, montane, and sedentary caribou herds

Authors

  • MARYLÈNE BOULET,

    1. Département de Biologie, Université Laval, Québec, QC, Canada G1K 7P4,
    2. Centre d’études nordiques, Université Laval, Québec, QC, Canada G1K 7P4,
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  • SERGE COUTURIER,

    1. Département de Biologie, Université Laval, Québec, QC, Canada G1K 7P4,
    2. Centre d’études nordiques, Université Laval, Québec, QC, Canada G1K 7P4,
    3. Ministère des Ressources naturelles et de la Faune, Direction de la recherche sur la faune, 880 Ch. Ste-Foy, 2th floor, Québec, QC, Canada G1S 4X4,
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  • STEEVE D. CÔTÉ,

    1. Département de Biologie, Université Laval, Québec, QC, Canada G1K 7P4,
    2. Centre d’études nordiques, Université Laval, Québec, QC, Canada G1K 7P4,
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  • ROBERT D. OTTO,

    1. Wildlife Division, Department of Environment and Conservation, PO Box 2007, Corner Brook, NL, Canada A2H 7S1
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    • Present address: Institute for Biodiversity, Ecosystem Science, and Sustainability, Sir Wilfred Grenfell College, 1 University Drive, Corner Brook, NL, Canada A2H 6P9

  • LOUIS BERNATCHEZ

    1. Département de Biologie, Université Laval, Québec, QC, Canada G1K 7P4,
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Marylène Boulet, Department of Biological Anthropology and Anatomy, Box 90383, 08 Bio Science Bldg, Duke University, Durham, NC 27708, USA. Fax: 919-660-7348; E-mail: marylene.boulet@duke.edu

Abstract

Genetic differentiation is generally assumed to be low in highly mobile species, but this simplistic view may obscure the complex conditions and mechanisms allowing genetic exchanges between specific populations. Here, we combined data from satellite-tracked migratory caribou (Rangifer tarandus), microsatellite markers, and demographic simulations to investigate gene flow mechanisms between seven caribou herds of eastern Canada. Our study included one montane, two migratory, and four sedentary herds. Satellite-tracking data indicated possibilities of high gene flow between migratory herds: overlap of their rutting ranges averaged 10% across years and 9.4% of females switched calving sites at least once in their lifetime. Some migratory individuals moved into the range of the sedentary herds, suggesting possibilities of gene flow between these herds. Genetic differentiation between herds was weak but significant (FST = 0.015): migratory and montane herds were not significantly distinct (FST all ≤ 0.005), whereas sedentary herds were more differentiated (FST = 0.018–0.048). Geographical distances among sedentary herds limited gene flow. Historical estimates of gene flow were higher from migratory herds into sedentary herds (4Nm all > 9) than vice-versa (4Nm all < 5), which suggests migratory herds had a demographic impact on sedentary herds. Demographic simulations showed that an effective immigration rate of 0.0005 was sufficient to obtain the empirical FST of 0.015, while a null immigration rate increased the simulated FST to > 0.6. In conclusion, the weak genetic differentiation between herds cannot be obtained without some genetic exchanges among herds, as demonstrated by genetic and spatial data.

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