added by admin on January 17, 2012
SIBERIA, a name that conjures up images of snow and ice, may have been an unlikely refuge from the bitter cold of the last ice age. Ancient DNA from the region paints a picture of remarkably stable animal and plant life in the teeth of plunging temperatures. The findings could help predict how ecosystems will adapt to future climate change.
The permanently frozen soil of Siberia, Canada and Alaska preserves the DNA of prehistoric plants, fungi and animals. “It’s a giant molecular freezer,” says James Haile at Murdoch University in Perth, Western Australia.
Glacial ice can also contain ancient DNA but permafrost is much more abundant than ice and so should provide a more complete picture of the effects of prehistoric climate change, says Haile. Last month, at the International Barcode of Life Conference in Adelaide, South Australia, his colleague Eva Bellemain of the University of Oslo in Norway revealed the first fruits of their analysis of Siberian permafrost DNA.
The samples were extracted from 15,000 to 25,000-year-old frozen sediment in southern Chukotka in north-eastern Siberia. Their age is significant: around 20,000 years ago temperatures plummeted and ice sheets blanketed much of the northern hemisphere – but parts of Siberia, Canada and Alaska apparently stayed ice-free (Quaternary Science Reviews, DOI: 10.1016/j.quascirev.2011.07.020).
Fossils and pollen found in these regions suggest they may have acted as a refuge for plants and animals during this time, but Bellemain turned to fungal DNA to get a complete picture of the environment. Many fungi consume plants, and so indicate the plant life around at the time.
Using 23 permafrost cores, Bellemain identified around 40 fungal taxa that thrived during the last ice age. “We didn’t expect to find so much,” she says.
The diversity of fungi found suggests that a brimming plant community thrived in northern Siberia to support them. This range of plants should also have sustained a diverse assembly of mammals – and the samples indeed contain DNA from woolly rhinoceros (Coelodonta antiquitatis), woolly mammoths (Mammuthus primigenius), reindeer (Rangifer tarandus) and moose (Alces alces) dating back to between 15,000 and 25,000 years ago (Molecular Ecology, DOI: 10.1111/j.1365-294x.2011.05306.x).
Meanwhile, Haile and Tina Jørgensen at the University of Copenhagen in Denmark have used ancient DNA together with pollen and fossil evidence to reconstruct the plant life surrounding Lake Taymyr, on the Taymyr peninsula in northern Siberia. Using 18 cores from five sites around the lake, the team identified 66 plant taxa that stuck around from 46,000 to 12,000 years ago, even though temperatures in the region fluctuated by some 20 °C during this period. “I was surprised that the [living] environment remained stable for so long,” says Jørgensen (Molecular Ecology, DOI: 10.1111/j.1365-294x.2011.05287.x).
The result does not surprise Gregory Retallack at the University of Oregon in Eugene, who studies plant remains in ancient soils that have been fossilised. “A part of this stability is down to the inertia of ecosystems,” he says.
Haile and colleagues are now keen to analyse other samples to uncover how the prehistoric flora and fauna in Canada and Alaska were affected by climate change.
Andrew Lowe at the University of Adelaide thinks the results could be used in climate models “to tell us how future communities will change”. But Retallack thinks such predictions will not be possible until we know, for example, how the flora and fauna were affected by large pulses of warming 70,000 and 125,000 years ago.