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Conservation Genetics

, Volume 15, Issue 6, pp 1357–1369 | Cite as

Cryptic structure and niche divergence within threatened Galápagos giant tortoises from southern Isabela Island

  • D. L. EdwardsEmail author
  • R. C. Garrick
  • W. Tapia
  • A. Caccone
Research Article

Abstract

Although Galápagos giant tortoises are an icon for both human-mediated biodiversity losses and conservation management successes, populations of two species on southern Isabela Island (Chelonoidis guntheri, and C. vicina) remain threatened by hunting and persistence of feral animals. Conservation management of these tortoises has been hampered by lack of clarity regarding their taxonomy, ecological and morphological diversity, and the spatial distribution of evolutionarily significant units that may exist. Analyses of 16 microsatellite loci did not group samples according to current taxonomy. Instead, three (rather than two) genetic clusters were revealed. We show that the three regions of southern Isabela associated with these genetic clusters are significantly different in their ecological niches, which could suggest that ecological divergence may have shaped patterns of genetic differentiation in these tortoises. Furthermore, results suggest limited recent gene flow among sampled localities and between each of the three regions associated with genetic clusters. We discuss the need for further research on the ecological factors shaping the genetic and morphological diversity of southern Isabela tortoises. We suggest that current strategies whereby populations are managed separately are warranted pending further study, but due to mixed ancestry we recommend that Cerro Paloma tortoises be excluded from management programs.

Keywords

Chelonoidis Conservation Management Ecological divergence Evolutionarily significant unit Galápagos tortoise Genetic divergence 

Notes

Acknowledgments

We thank the PNG for instrumental support for this project and the collection of tortoise distribution data, Alizon Llerena for distribution data curation and Linda Cayot (Galápagos Conservancy) for discussion of ideas and invaluable comments on this manuscript. We thank two anonymous reviewers for improving the manuscript. Permits for sample collection were granted by the PNG, and CITES permits (12US209142) were issued by the US Fish & Wildlife Service. Financial support came from the PNG, CDF and Yale Institute for Biospheric Studies.

Supplementary material

10592_2014_622_MOESM1_ESM.docx (415 kb)
Supplementary material 1 (DOCX 416 kb)

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Copyright information

© Springer Science+Business Media Dordrecht 2014

Authors and Affiliations

  • D. L. Edwards
    • 1
    Email author
  • R. C. Garrick
    • 2
  • W. Tapia
    • 3
  • A. Caccone
    • 1
  1. 1.Department of Ecology and Evolutionary BiologyYale UniversityNew HavenUSA
  2. 2.Department of BiologyUniversity of MississippiUniversityUSA
  3. 3.Parque Nacional de GalápagosPuerto AyoraEcuador

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