Einstein Science Reporting for Kids
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3-Oct-2003

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The tortoise and the volcano



Giant Galápagos tortoises that survived an explosive volcanic eruption about 100,000 years ago. Image/Artwork courtesy of Luciano Beheregaray.
Click here for a high resolution photograph.

In the Aesop's fable, "The Tortoise and the Hare," the slow and steady tortoise defeats the speedy yet over-confident hare and reminds us of the value of never giving up. The giant Galápagos tortoises that survived an explosive volcanic eruption about 100,000 years ago never gave up either. In a new study, scientists report that the tortoises living on the volcano's slopes today, the descendants of the eruption survivors, carry a record of the eruption in their genetic make-up.

The authors say that the eruption left its mark when it killed off much of the tortoise population. This caused a dramatic reduction in genetic variety, a situation known as a "genetic bottleneck."

The scientists analyzed the genetic diversity of separate populations of giant tortoises from the same island in the Galápagos. Each population of tortoises studied lives on the slopes of a different volcano.

They report that the genetic diversity found in tortoises on the slopes of Alcedo, a volcano with an explosive eruption in its past, is lower than the genetic diversity of tortoise populations from volcanoes with less explosive eruptions in their past. The timing of the drop in genetic variation seems to agree with the timing of the eruption, the researchers say. This research appears in the 03 October issue of the journal Science published by AAAS the science society.

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