Ancient DNA elucidates the lost world of western Indian Ocean giant tortoises and reveals a new extinct species from Madagascar

A new extinct species of giant tortoise from Madagascar, previously unknown to science, has been identified using ancient DNA analysis. This discovery sheds light on the lost biodiversity of the western Indian Ocean, revealing a complex history of colonization and extinction. Researchers combined ancient DNA, phylogenetic, ancestral range, and molecular clock analyses with radiocarbon and paleogeographic evidence to trace the evolutionary journey of these tortoises. Findings indicate that the ancestor of extinct Mascarene tortoises dispersed from Africa in the Eocene, colonizing now-sunken islands northeast of Madagascar before spreading to the Mascarenes. Another dispersal event in the latest Eocene/Oligocene led to the evolution of giant, large, and small tortoise species on Madagascar, with two giants and one large species disappearing around 1000 to 600 years ago. The study also traces the colonization of the Granitic Seychelles from Madagascar in the Early Pliocene and Aldabra from the Seychelles in the Late Pleistocene, highlighting the impact of human activity on these populations.

Kehlmaier, C., Graciá, E., Ali, J. R., Campbell, P. D., Chapman, S. D., Deepak, V., Ihlow, F., Jalil, N.-E., Pierre-Huyet, L., Samonds, K. E., Vences, M., & Fritz, U. (2023). Ancient DNA elucidates the lost world of western Indian Ocean giant tortoises and reveals a new extinct species from Madagascar. Science Advances, 9(2). https://doi.org/10.1126/sciadv.abq2574