11/01/2017 - Extinct Giant Tortoise - 1,000-year-old DNA decoded
Dresden, 01/11/2017. Scientists from Senckenberg and the University of Potsdam studied the genetic material of the extinct giant tortoise Chelonoidis alburyorum. The international team succeeded for the first time in obtaining a complete DNA sequence of these tropical animals. The genetic material reveals that the Bahamas Tortoise was closely related to Galapagos Tortoises and the South American Chaco Tortoise. In their study, published today in “Proceedings B,” the journal of the Royal Society of London, the scientists also present evidence that the animals became extinct due to human activity.
Approximately 1,000 years ago, the giant tortoise Chelonoidis alburyorum still made its home in the Bahamas – but that changed shortly after the islands were settled by humans. “Today, we can only find fossil remains of this tortoise, which reached a length of about half a meter,” says Professor Uwe Fritz, director of the Senckenberg Natural History Collections in Dresden, and he continues, “For the first time, we examined the Bahama Tortoise’s genetic material and were able to determine that these animals, who became extinct approximately 850 years ago, were closely related to Galapagos Tortoises and the Chaco Tortoise from South America.”
Surprisingly, the closest relatives of these terrestrial tortoises and two additional South American species occur in Africa, as shown by the study’s results. This indicates that in the course of geological history, the group of turtles under examination must have spread across the oceans several times, for example by rafting, thus traveling from Africa to South America and thence to the Galapagos Islands and the Bahamas.
Using highly specialized laboratory methods, the international team led by the scientist from Dresden and Professor Michael Hofreiter of the University of Potsdam was able for the first time to obtain genetic data – an almost complete mitochondrial genome – from a 1,000-year-old humerus of the giant tortoise and compare it with modern species. This was made possible by the relatively well preserved
DNA, which is unusual for the tropics. “The fossils we examined came from so-called “blue holes” – those are karst sink-holes filled with sea water that apparently allow for a relatively high level of DNA preservation,” explains Hofreiter. This opens new possibilities for the examination of the DNA from extinct tropical animals.
The giant tortoises disappeared only a few years after the Bahamas were settled by humans – long before Christopher Columbus discovered America. Fritz explains, “This is a general pattern, since many larger species of animals disappeared from the Bahamas and the Antilles shortly after the arrival of human settlers. It shows that even early on, humans did not live in harmony with nature but excessively exploited food sources and changed habitats from the beginning. However, compared to the early days, today this process occurs at such an alarming speed that the loss of species and the impoverishment of our environment have taken on a threatening dimension.”
At least, in the future, genetic material from the “blue holes” may increase our understanding of which species have long since been irretrievably lost and which biological communities might be found there without human interference.
Prof. Dr. Uwe Fritz
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To study and understand nature with its unlimited diversity of living creatures and to preserve and manage it in a sustainable fashion as the basis of life for future generations – that has been the goal of the Senckenberg Gesellschaft für Naturforschung (Senckenberg Nature Research Society) for almost 200 years. This integrative “geobiodiversity research” and the dissemination of research and science are among Senckenberg’s primary tasks. Three nature museums in Frankfurt, Görlitz and Dresden display the diversity of life and the earth’s development over millions of years. The Senckenberg Gesellschaft für Naturforschung is a member of the Leibniz Association. The Senckenberg Nature Museum in Frankfurt is supported by the City of Frankfurt am Main as well as numerous other partners. Additional information can be found at www.senckenberg.de
200 years of Senckenberg! 2017 marks Senckenberg’s anniversary year. For 200 years, the society, which was founded in 1817, has dedicated itself to nature research with curiosity, passion and involvement. Senckenberg will celebrate its 200-year success story with a colorful program consisting of numerous events, specially designed exhibitions and a grand museum party in the fall. Of course, the program also involves the presentation of current research and future projects. Additional information can be found at: www.200jahresenckenberg.de.