An international team of researchers led by the University of Adelaide suggests that climate change is the likely cause of the mysterious disappearance of ancient lions and bears from parts of North America for a thousand years or more before the last period glacial.
In a study in Molecular ecology, the researchers sequenced the DNA of cave lion and bear fossils from North America and Eurasia to better understand the timing and drivers of their past movements between continents.
Co-author Dr Kieren Mitchell of the Australian Center for Ancient DNA at the University of Adelaide said: “There is a common perception that apart from mass extinctions or direct human interference, ecosystems have tend to remain stable over thousands, if not millions of years. “
“As our study of the fossil record illustrates, this is not necessarily the case.”
âPrevious research has shown that brown bears (or grizzly bears) were extinct from parts of North America for thousands of years before the last ice age. By the time people crossed the bridge to North America North too. â
“But no one knows exactly why they went missing in the first place, which is why studying this event is important.”
A key finding from the new research is that cave lions in the same region went extinct more than once – before their final extinction, they also went extinct and reappeared thousands of years later, at roughly the same moment that bears. There is no evidence that people caused these temporary disappearances, and the cold conditions of the Ice Age were not to blame.
âInstead, it looks like a smoking gun indicating some kind of change in their ecosystem,â Dr. Mitchell said.
The timing of lion and bear extinction in parts of North America (particularly Alaska and the Yukon Territory) coincides with evidence of widespread vegetation change in the region. The researchers suggest that the warm temperatures before the last ice age may have caused a change in the abundance of different types of plants, which had ripple effects on herbivores and then on their predators (such as bears and lions).
The colder temperatures leading up to the last Ice Age may have reversed this change and made the region more hospitable to herbivores, and in turn their predators.
“Overall, these results demonstrate how changing ecosystems in the past have been, and also how the abundance of different species can be very sensitive to climate change,” said Dr Mitchell.
Senior University of Adelaide author Dr Alexander Salis said that “the dispersal patterns shared between lions and bears correspond to the presence of the Bering Land Bridge that connected Russia and Alaska for the ice ages “.
“The bridge has been periodically exposed and inundated by sea level changes during the last ice ages, allowing an intermittent dispersal of animals and people between continents and altering the makeup of the fauna.”
“While many might think that species arrive in an area and stay there, we show that the past was much more dynamic, involving multiple waves of dispersal and local extinctions in this case.”
Ancient DNA reveals the evolution of giant bears in the
Alexander T. Salis et al, Lions and brown bears colonized North America in several synchronous waves of dispersal across the Bering Land Bridge, Molecular ecology (2021). DOI: 10.1111 / mec.16267
Quote: Solve the disappearance of bears and lions with ancient DNA (2022, January 4) retrieved January 4, 2022 from https://phys.org/news/2022-01-lions-ancient-dna.html
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