Scientists have warned that genetic diversity may diminish with animal adventures in new areas due to global warming, making them vulnerable to extinction, after tracking the impact of climate change on American mastodons.
Huge, hairy and a pair of fearsome tusks, mastodons resemble plump, bushy elephants. The earliest fossils of American mastodons date back about 3.5-4 million years ago with the creatures commonly found in woodland and swamp areas as they roamed trees and shrubs.
But 11,000 years ago it became extinct – perhaps, experts say, due to a combination of climate change and human hunting.
Researchers now say that analyzing ancient mitochondrial DNA has shed new light on the effect of global heating and cooling on the monsters.
“As the temperature increased, they followed an expansion of forests and swamps as they moved north,” said Professor Hendrik Poinar, co-author of the research from McMaster University in Canada.
But their fortunes were reversed with climate change. “With climate change, it cooled again, it became restricted in the north and ultimately couldn’t deal with environmental change, and it became extinct locally,” he said.
Crucially, the team found that genetic diversity was lower among the animals that moved north. As species including moose and beavers move north today as a result of global warming, the team says the finding is important because it indicates that such species could become less resistant to more pressures. .
Emil Karpinski, another author of the research from McMaster University, said.
Writing in the journal Nature CommunicationsPoinar and colleagues report how they analyzed ancient mitochondrial DNA extracted from the remains of 35 American mastodons from all over North America.
By comparing mitochondrial genomes, the team discovered that animals divide into five main groups, while one makes up a sixth of their own. Two of the five major groups largely include mastodons from Alaska and the Yukon. Mastodons from one of these groups have been dated to an interglacial period spanning from 130,000 to 80,000 years ago. However, the mastodons in the other group were much older, indicating that they were part of separate migrations during earlier interglacial periods.
The team says the results indicate that the mastodon animals moved north in small numbers on multiple occasions as the ice sheets retreated, but vanished in the area as the climate cooled and the ice returned – a theory supported by declining genetic diversity in these two groups.
The team adds that such migrations may have been a widespread phenomenon that affected other animals in North America at that time, such as the western camel.
They write: “Presumably, similar processes occurred in Eurasia, with heat-adapted species such as hippos and hyenas, accidentally expanding their ranges northward during previous glacial formations to formerly ice-dominated regions such as the British Isles and Scandinavia.”
Professor Love Dahlen, from the Center for Palaeogenetics in Sweden who was not involved in the work, welcomed the research. “This is an amazing study that uses ancient DNA to go back in time to the last time the Earth was in a warming period more than a hundred thousand years ago,” he said.
Dalin said finding that northern mastodons were not able to return to the south when the climate got cold is also a lesson.
“This is important because it indicates that when climate change causes the range of species to shrink, then this is characterized by the extinction of populations at the margins of the range rather than the migration of populations to more suitable habitats.”