Population structure of Columbia spotted frogs (Rana luteiventris) is strongly affected by the landscape

Authors

  • W. CHRIS FUNK,

    Corresponding author
    1. Division of Biological Sciences, University of Montana, Missoula, Montana 59812, USA,
      W. C. Funk, Present address: Integrative Biology, University of Texas, 1 University Station C0930, Austin, TX 78712, USA; Fax: 512 4719651; E-mail: wcfunk@mail.utexas.edu
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  • MICHAEL S. BLOUIN,

    1. Department of Zoology, Oregon State University, 3029 Cordley Hall, Corvallis, OR 97331, USA,
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  • PAUL STEPHEN CORN,

    1. US Geological Survey, Aldo Leopold Wilderness Research Institute, 790 E. Beckwith Ave., Missoula, MT 59807, USA,
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  • BRYCE A. MAXELL,

    1. Wildlife Biology Program, College of Forestry and Conservation, University of Montana, Missoula, MT 59812, USA,
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  • DAVID S. PILLIOD,

    1. Aldo Leopold Wilderness Research Institute, Rocky Mountain Research Station, USDA Forest Service, 790 E. Beckwith Ave., Missoula, MT 59807, USA
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  • STEPHEN AMISH,

    1. Wildlife Biology Program, College of Forestry and Conservation, University of Montana, Missoula, MT 59812, USA,
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  • FRED W. ALLENDORF

    1. Division of Biological Sciences, University of Montana, Missoula, Montana 59812, USA,
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W. C. Funk, Present address: Integrative Biology, University of Texas, 1 University Station C0930, Austin, TX 78712, USA; Fax: 512 4719651; E-mail: wcfunk@mail.utexas.edu

Abstract

Landscape features such as mountains, rivers, and ecological gradients may strongly affect patterns of dispersal and gene flow among populations and thereby shape population dynamics and evolutionary trajectories. The landscape may have a particularly strong effect on patterns of dispersal and gene flow in amphibians because amphibians are thought to have poor dispersal abilities. We examined genetic variation at six microsatellite loci in Columbia spotted frogs (Rana luteiventris) from 28 breeding ponds in western Montana and Idaho, USA, in order to investigate the effects of landscape structure on patterns of gene flow. We were particularly interested in addressing three questions: (i) do ridges act as barriers to gene flow? (ii) is gene flow restricted between low and high elevation ponds? (iii) does a pond equal a ‘randomly mating population’ (a deme)? We found that mountain ridges and elevational differences were associated with increased genetic differentiation among sites, suggesting that gene flow is restricted by ridges and elevation in this species. We also found that populations of Columbia spotted frogs generally include more than a single pond except for very isolated ponds. There was also evidence for surprisingly high levels of gene flow among low elevation sites separated by large distances. Moreover, genetic variation within populations was strongly negatively correlated with elevation, suggesting effective population sizes are much smaller at high elevation than at low elevation. Our results show that landscape features have a profound effect on patterns of genetic variation in Columbia spotted frogs.

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