The evolutionary origin of Indian Ocean tortoises (Dipsochelys).


Journal Article

Today, the only surviving wild population of giant tortoises in the Indian Ocean occurs on the island of Aldabra. However, giant tortoises once inhabited islands throughout the western Indian Ocean. Madagascar, Africa, and India have all been suggested as possible sources of colonization for these islands. To address the origin of Indian Ocean tortoises (Dipsochelys, formerly Geochelone gigantea), we sequenced the 12S, 16S, and cyt b genes of the mitochondrial DNA. Our phylogenetic analysis shows Dipsochelys to be embedded within the Malagasy lineage, providing evidence that Indian Ocean giant tortoises are derived from a common Malagasy ancestor. This result points to Madagascar as the source of colonization for western Indian Ocean islands by giant tortoises. Tortoises are known to survive long oceanic voyages by floating with ocean currents, and thus, currents flowing northward towards the Aldabra archipelago from the east coast of Madagascar would have provided means for the colonization of western Indian Ocean islands. Additionally, we found an accelerated rate of sequence evolution in the two Malagasy Pyxis species examined. This finding supports previous theories that shorter generation time and smaller body size are related to an increase in mitochondrial DNA substitution rate in vertebrates.

Full Text

Cited Authors

  • Palkovacs, EP; Gerlach, J; Caccone, A

Published Date

  • August 2002

Published In

Volume / Issue

  • 24 / 2

Start / End Page

  • 216 - 227

PubMed ID

  • 12144758

Pubmed Central ID

  • 12144758

Electronic International Standard Serial Number (EISSN)

  • 1095-9513

International Standard Serial Number (ISSN)

  • 1055-7903

Digital Object Identifier (DOI)

  • 10.1016/s1055-7903(02)00211-7


  • eng