Oct. 14, 2008 -- DNA in the bones of Adelie penguins that survived the last ice age are helping to shed light on how other animals will cope with climate change, say researchers.
Evolutionary biologist Professor David Lambert of Griffith University in Brisbane and colleagues report their analysis of Adelie penguin DNA dating back to 37,000 years in the journal PLoS Genetics.
"Adelie penguins are a wonderful model to study the problem of climate change," said Lambert. "They have lived through temperature fluctuations much higher than those in equatorial regions."
Lambert said Adelie penguins have survived several degrees of warming since the last glacial maximum 18,000 years ago.
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And he expects them to have been around 120,000 years earlier than that, during the peak of the ice age before last.
Adelie penguins are one of very few species that have survived in large numbers over such a long time, said Lambert.
If species are able to move geographically, there is evidence that they can combat climate change by staying within their preferred temperature range, he added.
"The problem for Adelie penguins is they've got nowhere to go," he said. "They're in the coldest place they can be."
The fact Adelie penguins have survived extreme changes in temperature may mean that some species are able to respond to climate change even when they can't move geographically.
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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