Ancient DNA Sheds New Light on History of Giant Tortoises

Using various genomics and other technologies, a team led by scientists from the Senckenberg Museum of Zoology in Germany have uncovered new details about the migration of ancient giant tortoises from Africa to Madagascar and other nearby islands. Before the arrival of humans, giant tortoises dominated the ecosystems of the oceanic islands in the western Indian Ocean. To better understand the diversity and biogeography of these animals —many species of which are long extinct — the researchers created near-complete mitochondrial genomes from fossils of tortoise species found on Madagascar and the Granitic Seychelles, as well as museum specimens collected hundreds of years ago. As reported in this week's Science Advances, they combined these sequences with ancient DNA, phylogenetic, ancestral range, and molecular clock analyses alongside radiocarbon and paleogeographic evidence to reveal the biogeography and original diversity of the western Indian Ocean tortoise fauna. In doing so, the investigators also discover a previously unknown extinct large-sized tortoise species from Madagascar and propose a dispersal scenario for all western Indian Ocean tortoise species.