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Global heating motivated American mastodons to trek north

Shift led to local extinctions and could have important implications for species today

Genetic diversity could shrink as animals venture into new territories because of global heating leaving them vulnerable to extinction, scientists have warned after tracking the impact of climate change on the American mastodon.

Huge, hairy and with a pair of fearsome tusks, mastodons resembled stocky, hirsute elephants. The earliest fossils of American mastodons date to about 3.5-4m years ago with the creatures commonly found in wooded and swampy areas where they browsed on trees and shrubs.

But by 11,000 years ago they were extinct – probably, experts say, because of a combination of climate change and human hunting.

Now researchers say an analysis of ancient mitochondrial DNA has shed new light on the impact of global heating and cooling on the beasts.

“As the temperature warmed, they followed expanding forest and swampy niches as they moved north,” said Prof Hendrik Poinar, co-author of the research from McMaster University in Canada.

But their fortunes reversed with the climate. “As the climate changed, cooling again, they became restricted in the north and couldn’t ultimately handle the environmental change and went locally extinct,” he said.

Crucially, the team found genetic diversity was lower among the animals that moved north. With species including moose and beavers moving northwards today as a result of global heating, the team says the finding is important as it suggests such species could become less resilient to further pressures. .

“While it might not have been too big a problem for American mastodons it might not bode well for extant species if the same patterns are true and they trade their southern populations and ranges for new ones in the north,” said Emil Karpinski, another author of the research from McMaster University.

Writing in the journal Nature Communications, Poinar and colleagues report how they analysed ancient mitochondrial DNA extracted…

Nicola Davis

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