Conservation Genetics

, Volume 12, Issue 2, pp 449–459 | Cite as

Effect of human-mediated migration and hybridization on the recovery of the American crocodile in Florida (USA)

  • David RodriguezEmail author
  • Michael R. J. Forstner
  • Paul E. Moler
  • Joseph A. Wasilewski
  • Michael S. Cherkiss
  • Llewellyn D. Densmore III
Research Article


The American crocodile (Crocodylus acutus) is a large apex predator with an extensive but fragmented range. Crocodylus acutus suffered a population crash and was almost extirpated from Florida (USA) during the 1970s; however, in 2007 it was federally downlisted from endangered to threatened based on an increase of suitable habitat and a growing population. A genetic assessment of this population has not been performed even though foreign crocodiles have been released into Florida waters. Herein, we use mitochondrial and nuclear DNA markers to characterize relationships among American crocodiles along the southern coast of Florida and reference samples from other countries. We detected inter- and intra-specific hybridization and unexpected population structure attributed to human-mediated migration of crocodiles from Latin America and the Greater Antilles. Our results suggest that the population size of crocodiles actually native to Florida should be reevaluated, particularly in light of ongoing admixture in this population. We reemphasize the utility of genetic markers in conservation and management programs for endangered species; especially those that can hybridize with closely related congeners. The American crocodile in Florida has recovered owing to successful conservation initiatives, but a long-term management protocol that takes genetic data into account is still needed.


Crocodylus Endangered species recovery Human-mediated migration Hybridization Population genetics 



We dedicate this manuscript to the memories of John Thorbjarnarson and John Behler. We also thank Perran Ross, Jorge Salazar-Bravo, Guillermo Velo-Antón, and Frank Mazzotti for reviewing earlier versions of this manuscript. We also thank Jeremy Weaver, Rogelio Cedeño-Vázquez, Dnate’ Baxter, John Hanson, Robert Bradley, Diana McHenry, Shawn McCracken, Julie Parlos, Trina Guerra, Jim Lindsay, Bob Bertelson, Jon Holderman, Mario Aldecoa, Florida Power & Light, and the Zamudio Lab at Cornell University. This work was supported by a National Science Foundation Graduate Research Fellowship (DR), a Predoctoral Summer Fellowship from Texas State University (DR), and National Science Foundation grant BSR-0444133 (LDD).

Supplementary material

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Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  • David Rodriguez
    • 1
    Email author
  • Michael R. J. Forstner
    • 2
  • Paul E. Moler
    • 3
  • Joseph A. Wasilewski
    • 4
  • Michael S. Cherkiss
    • 5
  • Llewellyn D. Densmore III
    • 6
  1. 1.Department of Ecology and Evolutionary BiologyCornell UniversityIthacaUSA
  2. 2.Department of BiologyTexas State UniversitySan MarcosUSA
  3. 3.Florida Fish & Wildlife Conservation CommissionGainesvilleUSA
  4. 4.Natural Selections of South FloridaPrincetonUSA
  5. 5.University of Florida-FLRECFort LauderdaleUSA
  6. 6.Department of Biological SciencesTexas Tech UniversityLubbockUSA

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