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Penguin DNA Suggests Special Climate Coping

Anna Salleh, ABC Science Online

Lambert and colleagues' research on the rate of evolution of Adelie penguins in Antarctica may help shed some light on why this is the case.

The team analyzed the number of mutations in the mitochondrial DNA of mothers and their chicks and compared this with DNA from ancestral penguins, taken from 37,000-year-old bones preserved in the extreme cold and dry conditions of Antarctica.

They found the rate of mutations between generations was the same as the rate over 37,000 years.

This is contrary to recent suggestions that evolution is faster over short time frames but slows down over long time frames, when the loss of genetic diversity due to speciation is taken into account.

Importantly, the rate of evolution of Adelie penguins found by Lambert and the team confirm earlier findings that the penguins evolve faster than previously thought, which may be one explanation for their ability to survive extreme variations in climate.

Other animals which have similarly high rates of evolution are the tuatara (a New Zealand reptile), bison, brown bear and cave lion, said Lambert.

The DNA analysis has so far focused on genes not subject to natural selection.

These so-called "neutral" genes are important in developing an evenly ticking "molecular clock" for evolution, said Lambert. Sequences under control of natural selection would change rapidly during some periods of time and hardly change at all at other periods.

Evolutionary biologist Jeremy Austin of the University of Adelaide said the work raises questions about the idea that evolution rates are time-dependent.

But, he said, it is possible that 37,000 years is not long enough for the slower evolutionary rate to show up.

"When we talk about evolutionary rates, we're talking about things that are possibly a million years or more," Austin said. Sequencing even older DNA would be helpful as comparing Adelie penguins with a sister species, he added.

Lambert said he is confident the team will be able to obtain viable DNA from penguin remains preserved for hundreds of thousands of years many feet beneath the permafrost.

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