Combining genetic markers and stable isotopes to reveal population connectivity and migration patterns in a Neotropical migrant, Wilson's warbler (Wilsonia pusilla)

Authors

  • Sonya M. Clegg,

    Corresponding author
    1. Center for Tropical Research, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA, 94132, USA,
      S. Clegg, Department of Biological Sciences, Imperial College at Silwood Park, Ascot, Berkshire, SL5 7PY, UK. Fax: +44 0207 59 42339; E-mail: sonya.clegg@ic.ac.uk
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  • Jeffrey F. Kelly,

    1. Rocky Mountain Research Station, 333 Broadway SE, Suite 115, Albuquerque, NM 87102 USA,
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    • Present address: Oklahoma Biological Survey and Department of Zoology, University of Oklahoma, Norman, OK, 73019, USA.

  • Mari Kimura,

    1. Center for Tropical Research, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA, 94132, USA,
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  • Thomas B. Smith

    1. Center for Tropical Research, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA, 94132, USA,
    2. Center for Population Biology, University of California, Davis, CA, 95616, USA
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    • Present address: Department of Organismic Biology, Ecology, and Evolution; and Center for Tropical Research, Institute of the Environment, University of California, Los Angeles, CA, 90095–1606, USA.


S. Clegg, Department of Biological Sciences, Imperial College at Silwood Park, Ascot, Berkshire, SL5 7PY, UK. Fax: +44 0207 59 42339; E-mail: sonya.clegg@ic.ac.uk

Abstract

We used results from the analysis of microsatellite DNA variation and hydrogen stable-isotope ratios to characterize the population structure of a neotropical migrant passerine, the Wilson's warbler (Wilsonia pusilla). The resulting information was then used to infer migration patterns and population connectivity between breeding grounds in North America and overwintering areas in Mexico and Central America. The microsatellite data revealed genetic structure across the North American continent; populations in the west were found to significantly differ from the east. Minimal genetic structure was observed among western sites. The lack of isolation by distance and low variance in FST values suggests that gene flow could play an ongoing role in limiting genetic differentiation among sites in the western part of the distribution. However, additional information including estimates of effective population size and the proximity of the population to equilibrium is required before the role of gene flow can be assessed fully. Analysis of isotope data showed a negative relationship between latitude and hydrogen isotope ratios in breeding ground individuals. There was a positive relationship between wintering ground latitude and hydrogen isotope ratios for individuals that were genetically western in origin. This is consistent with a leapfrog pattern of migration, in which genetically western birds from the northernmost breeding areas overwinter at the most southerly locations in Central America. Additionally, isotopic ratios of western birds suggest that coastal breeders overwinter in western Mexico, while western birds from further inland and at high elevations overwinter in eastern Mexico. Using information from both genetic an isotopic approaches will probably be useful for identifying patterns of migration and population connectivity between breeding and overwintering areas, both important issues for conservation efforts, and may also contribute to investigation of the evolution of migration.

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