Conservation Genetics

, Volume 8, Issue 4, pp 797–807

Riverbeds demarcate distinct conservation units of the radiated tortoise (Geochelone radiata) in southern Madagascar

  • Sébastien Rioux Paquette
  • Sandra M. Behncke
  • Susan H. O’Brien
  • Rick A. Brenneman
  • Edward E. LouisJr.
  • François-Joseph Lapointe
Original Paper

DOI: 10.1007/s10592-006-9227-5

Cite this article as:
Paquette, S.R., Behncke, S.M., O’Brien, S.H. et al. Conserv Genet (2007) 8: 797. doi:10.1007/s10592-006-9227-5

Abstract

The radiated tortoise (Geochelone radiata) is an endangered species endemic to Madagascar. It inhabits the semiarid spiny forest of the southern part of the island, an ecosystem heavily affected by habitat destruction. Furthermore, illegal harvesting greatly threatens this species. The main objective of our study was to acquire better knowledge of its genetic structure, in order to take appropriate management decisions concerning, for instance, the reintroduction of confiscated individuals. Our hypothesis was that rivers represent effective barriers to tortoise dispersal despite the fact that they are dry most of the year. We used 13 polymorphic microsatellite markers to compare samples from six populations across the range of the species. All analyses (Fisher’s exact tests, FST values, AMOVA) indicated that the radiated tortoise exhibits moderate levels of genetic structure throughout its range. In addition, we used a multiple regression approach that revealed the importance of rivers to explain the observed structure. This analysis supported the role of the Menarandra and Manambovo Rivers as major barriers to the dispersal of most radiated tortoises, but Markov chain Monte Carlo simulations revealed that low levels of recurrent gene flow may explain why FST values were not higher. We identified three distinct conservation units with relatively high assignments rates (87%), which should be valuable for the management of the species. This is the first study to report the genetic structure of a species sampled throughout the Malagasy spiny forest.

Keywords

Genetic structureManagement unitsMicrosatellitesRadiated tortoiseMadagascar

Copyright information

© Springer Science+Business Media, Inc. 2006

Authors and Affiliations

  • Sébastien Rioux Paquette
    • 1
  • Sandra M. Behncke
    • 2
  • Susan H. O’Brien
    • 3
  • Rick A. Brenneman
    • 2
  • Edward E. LouisJr.
    • 2
  • François-Joseph Lapointe
    • 1
  1. 1.Département de Sciences BiologiquesUniversité de MontréalMontréalCanada
  2. 2.Center for Conservation and ResearchHenry Doorly ZooOmahaUSA
  3. 3.Macaulay InstituteAberdeenUK