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AncientDNAof extinct species fromthe Pleistocene andHolocene has provided valuable evolutionary insights. However, these are largely restricted to mammals and high latitudes because DNA preservation in warm climates is typically poor. In the tropics and subtropics, non-avian reptiles constitute a significant part of the fauna and little is known about the genetics of the many extinct reptiles from tropical islands. We have reconstructed the near-complete mitochondrial genome of an extinct giant tortoise fromthe Bahamas (Chelonoidis alburyorum) using an approximately 1 000-year-old humerus fromawater-filled sinkhole (blue hole) on Great Abaco Island. Phylogenetic and molecular clock analyses place this extinct species as closely related to Gala'pagos (C. niger complex) and Chaco tortoises (C. chilensis), and provide evidence for repeated overseas dispersal in this tortoise group. The ancestors of extant Chelonoidis species arrived in South America from Africa only after the opening of the Atlantic Ocean and dispersed from there to the Caribbean and the Gala'pagos Islands. Our results also suggest that the anoxic, thermally buffered environment of blue holes may enhance DNA preservation, and thus are opening a window for better understanding evolution and population history of extinct tropical species, which would likely still exist without human impact. [ABSTRACT FROM AUTHOR]