The Warren Mastodon, the first complete American mastodon skeleton found in the United States, is on display in Paul and Irma Milstein’s Hall of Advanced Mammals at the American Museum of Natural History. Photo credit: D. Finnin / © AMNH
New old DNA The study shows that mastodon populations in the north were less genetically diverse and more prone to extinction.
New research suggests that American mastodons were avid travelers who traveled long distances across North America in response to dramatic climate change during the Pleistocene Ice Ages. The study was carried out by an international team of scientists and published today in the journal Communication with naturealso shows that mastodon populations that migrated north to the Arctic during warm periods were less genetically diverse, making them critically endangered. The results could be useful for modern conservation science.
“Today you might think that seeing animals like brown bears in northern Canada and on the arctic islands is great, well beyond their historical range. They obviously benefit, just like these mastodons for a while, from natural climate change, ”said Ross MacPhee, senior curator in the museum’s mammalian department and one of the study’s authors. “However, this benefit can be very limited. It is important to realize that what we consider a beneficial change on one level for one species is not necessarily so good for another. ”
New research by an international team of scientists suggests that dramatic environmental changes associated with the shifting or melting of continental glaciers played a key role as American mastodons migrated north from their southern areas. Photo credit: McMaster University
Mastodons, which belong to a group closely related to modern elephants and extinct mammoths, were among the largest living land animals on earth at the time and migrated east to Nova Scotia and south to central Mexico from what is now Alaska and the Yukon. The species became extinct about 11,000 years ago along with other large mammals such as mammoths, saber-toothed cats, and giant ground sloths.
Mastodon fossils previously discovered in northern climates suggest that the species likely had a wide distribution, but scientists remained in the dark about when these migrations took place and whether mastodon populations made repeated trips or went only once. To find out more, the researchers reconstructed entire mitochondrial genomes from the fossilized teeth, tusks, and bones of 33 mastodons. The results show that in response to warming climates and melting ice sheets, the animals traveled extreme distances, from warmer environments to the northernmost parts of the continent.
The Warren Mastodon, the first complete American mastodon skeleton found in the United States, is on display in Paul and Irma Milstein’s Hall of Advanced Mammals at the American Museum of Natural History. Photo credit: D. Finnin / © AMNH
The Pleistocene, which began about 2.6 million years ago, was a long roller coaster ride – cold glacial periods interspersed with warmer periods when the ice sheets would retreat. During these warm “interglacials”, new forests and wetlands grew in previously frozen regions, providing animals such as the mastodon with new sources of food and luring them north.
“These mastodons lived in Alaska when it was warm, as well as Mexico and parts of Central America. These were not stationary populations. The data shows that there was constant movement back and forth, ”said evolutionary geneticist Hendrik Poinar, director of the Ancient DNA Center at McMaster University and author of the study.
The researchers suggest that studying how different ecologically adapted Pleistocene megafauna genetically and ecologically responded to such climate transitions may provide valuable information on how climate change is affecting modern species in the north.
“It’s really interesting because many species, like moose and beaver, are rapidly expanding their range up to ten to a hundred kilometers north every century,” said Emil Karpinksi, lead author of the study and a doctoral student at the Old DNA Center and Department of Biology from McMaster University.
The scientists also analyzed the genetics of the “pioneer” populations that made it to the north and found that their genetic diversity was very low.
“It’s always a danger signal to vertebrate species,” said Grant Zazula, study author and paleontologist with the Yukon government. “When you lose genetic diversity, you lose the ability to respond to new conditions. In this case, they weren’t up there long enough to adjust to northern conditions when they got cold again. ”
Reference: September 1, 2020, Nature communication.
DOI: 10.1038 / s41467-020-17893-z
The study was a collaboration between scientists from Canada, the United States, Mexico, and Australia and was based on samples donated by museums and research institutions across North America, including the American Museum of Natural History.
