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Gene flow between an endangered endemic iguana, and its wide spread relative, on the island of Utila, Honduras: when is hybridization a threat?

Does hybridization threaten an endangered iguana?

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Abstract

The island endemic Ctenosaura bakeri was listed as critically endangered by the IUCN Redlist Assessment in 2004, 7 years after it was recognized as a distinct species. C. bakeri occupies a portion of Utila, a small continental island located off the northern coast of Honduras. Habitat destruction and over-harvesting are among the top threats facing this species. In addition, morphological evidence of hybridization was recently documented, raising the concern that gene flow from the common and widely distributed C. similis could threaten the genetic distinctiveness of C. bakeri. We show that hybridization occurs only at low levels and is not a current threat to C. bakeri. All ctenosaurs captured for this study were identified to species level without difficulty; none had intermediate or mosaic phenotypes. Sequence analysis of mitochondrial and nuclear markers revealed only two individuals with introgressed genotypes. Molecular analysis of the previously described hybrid showed it to be heterozygous for C. bakeri and C. similis alleles. Hybridization between these two species is possible and occurs occasionally in the wild, and the rate of hybridization could increase if habitat destruction or changes in relative abundance increase the probability of interbreeding. However, the level of gene flow indicated by current data is too low to threaten C. bakeri with genetic swam** or deleterious fitness effects.

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Acknowledgments

This study would not have been possible without the help of many amazing field volunteers: Dennis Baulechner, Jeffery Corneil, Corey Shaffer, Jeff Liechty, Wendy Naira, Melissa Issis Medina, Sammy Nuñez, and Hadas Grushka, many thoughtful discussions with James Fordyce and Sally Horn, The Utila Iguana Research and Breeding Station, the Overseas Research Station on Roatan and David Evans, the Cayos Cochinos Foundation, the many offices of AFE-COHDEFOR, the multitude of local residents and guides, and grants to S.A.P. from Sigma ** and the International Iguana Foundation, and the Department of Ecology and Evolutionary Biology of the University of Tennessee, Knoxville. All procedures were approved by the University of Tennessee, Knoxville, Institutional Animal Care and Use Committee.

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Authors and Affiliations

  1. Department of Ecology and Evolutionary Biology, The University of Tennessee, 569 Dabney Hall, Knoxville, TN, 37996, USA

    Stesha A. Pasachnik, Benjamin M. Fitzpatrick & Arthur C. Echternacht

  2. Department of Ecology and Evolutionary Biology, Peabody Museum of Natural History, Yale University, New Haven, CT, 06520, USA

    Thomas J. Near

Authors
  1. Stesha A. Pasachnik
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  2. Benjamin M. Fitzpatrick
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  3. Thomas J. Near
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  4. Arthur C. Echternacht
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Correspondence to Stesha A. Pasachnik.

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Pasachnik, S.A., Fitzpatrick, B.M., Near, T.J. et al. Gene flow between an endangered endemic iguana, and its wide spread relative, on the island of Utila, Honduras: when is hybridization a threat?. Conserv Genet 10, 1247–1254 (2009). https://doi.org/10.1007/s10592-008-9692-0

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