Conservation Genetics

, Volume 10, Issue 6, pp 1683–1696 | Cite as

Population genetics of the endangered South American freshwater turtle, Podocnemis unifilis, inferred from microsatellite DNA data

  • Tibisay Escalona
  • Tag N. Engstrom
  • Omar E. Hernandez
  • Brian C. Bock
  • Richard C. Vogt
  • Nicole Valenzuela
Research Article


We studied the population genetics of Podocnemis unifilis turtles within and among basins in the Orinoco and Amazon drainages using microsatellites. We detected high levels of genetic diversity in all sampled localities. However, ‘M-ratio’ tests revealed a substantial recent population decline in ten localities, in accord with current widespread exploitation. Our results reveal a consistent pattern across multiple analyses, showing a clear subdivision between the populations inhabiting the Amazon and Orinoco drainages despite a direct connection via the Casiquiare corridor, and suggesting the existence of two biogeographically independent and widely divergent lineages. Genetic differentiation followed an isolation-by-distance model concordant with hypotheses about migration. It appears that migration occurs via the flooded forest in some drainages, and via river channels in those where geographic barriers preclude dispersal between basins or even among nearby tributaries of the same basin. These observations caution against making generalizations based on geographically restricted data, and indicate that geographically proximate populations may be demographically separate units requiring independent management.


Population structure Biogeography Gene flow Landscape genetics Conservation Evolution 



This work was partially supported by grants from The National Science Foundation (DBI-0511958 to T.E. and IOS0743284 to N.V.), from The Scott Neotropical Fund to T.E. and N.V., and from FONACIT (Proyecto de la Agenda Biodiversidad 2000001319 to FUDECI). We are indebted to D. Pearse and K. Seok for their input and help with some of the analyses, to J. W. Sites Jr for valuable comments, and to Felix Daza for help during field work. We thank the US Fish and Wildlife Service’s Office of Management Authority for CITES import permits, as well as CITES export and genetics resource permits issued by the agencies IBAMA, INRENA, and MPPA in Brazil, Peru, and Venezuela, respectively.


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Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  • Tibisay Escalona
    • 1
  • Tag N. Engstrom
    • 2
  • Omar E. Hernandez
    • 3
  • Brian C. Bock
    • 4
  • Richard C. Vogt
    • 5
  • Nicole Valenzuela
    • 1
  1. 1.Department of Ecology, Evolution and Organismal BiologyIowa State UniversityAmesUSA
  2. 2.Department of Biological SciencesCalifornia State UniversityChicoUSA
  3. 3.FUDECI, Fundación para el Desarrollo de las Ciencias Físicas, Matemáticas y Naturales. AvUniversidad, Bolsa a San FranciscoCaracasVenezuela
  4. 4.Instituto de BiologíaUniversidad de AntioquiaMedellínColombia
  5. 5.Instituto Nacional de Pesquisas da Amazônia (INPA)Coordenação de Pesquisas em Biologia Aquática (CPBA)ManausBrazil

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