Evolutionary Age of the Galápagos Iguanas Predates the Age of the Present Galápagos Islands (original) (raw)

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Evolutionary Age of the Galápagos Iguanas Predates the Age of the Present Galápagos Islands

Abstract

New geological findings suggest that volcanoes existed over the Galápagos hotspot long before today's islands emerged less than 5 million years ago. The evolution of some of Galápagos' biota might have taken place on these former islands. This study investigates the evolutionary history of two of the archipelagos' older vertebrate taxa, the endemic Galápagos marine and land iguana (genera_Amblyrhynchus_and_Conolophus_). Mitochondrial rDNA sequences (in total about one kilobase of the 12S and 16S genes) were obtained from all extant genera of the family Iguanidae and the outgroup_Oplurus._The phylogenetic analyses suggest that the Galápagos iguanas are sister taxa. Rate comparisons between the iguanid sequences and a corresponding set of sequences from ungulates with known fossil ages date their separation time at 10 million years, or more. The results strengthen the hypothesis that extended speciation times in the Galápagos are possible and provide an estimate of the minimum time inhabited islands of the archipelago may have existed.

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A. R. Hoelzel, Ed.

Address correspondence and reprint requests to the author at School of Biological Sciences, University of Wales at Bangor, Bangor, Gwynedd LL57 2UW, Great Britain. Fax: +44-1248-37-1644. E-mail: [email protected].

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