Woolly mammoths, woolly rhinos and other large vegetarians living in the polar north weathered the last ice age on a varied diet of shrubby flowering plants and grass, including relatives of chrysanthemums, carnations, honeysuckles, legumes and sunflowers.
"It’s always been believed that the Arctic steppe was dominated by grasses and grass-like plants, and we find that’s not the case at all," Eline Lorenzen, an evolutionary biologist at UC Berkeley who was part of the 10-year project, told NBC News.
The new picture of Arctic flora dating back 50,000 years shows a region covered in several families of flowering shrubs, with grasses only making up 20 percent of the flora before the ice sheets set in.
An international team led by Eske Willerslev, a geogeneticist at the University of Copenhagen, collated sequencing data from a range of sources: permafrost samples from 21 locations, roundworm DNA from Arctic soils, and the stomach contents and fossilized poo of megafauna like mammoths, rhino and bison.
Hardy pollen of ancient plants lingering in soil or fossil samples are the usual clues to plant cover of the past. But this new survey relies instead on sequencing DNA, thereby including plants that didn't produce long-lasting or abundant pollen.
The team found evidence flowering plants in permafrost samples that also contained DNA from the large beasts, as well as in their stomach contents and poo. The more nutritious flowering plants may have been able to better feed them, the researchers propose in a paper published in the Wednesday issue of Nature.
The plants died out after the ice sheets peaked, around 20,000 years ago, about the same time the mammoths disappeared, and were replaced by woody, grassy species.
"When temperatures go back to what they were prior, it was a whole new community," Lorenzen said.