Solving the disappearance of bears and lions with ancient DNA

Date:
January 4, 2022
Source:
University of Adelaide
Summary:
Researchers suggest a change in climate is the likely cause of the
mysterious disappearance of ancient lions and bears from parts
of North America for a thousand years or more prior to the last
Ice Age.



FULL STORY ==========================================================================
An international team of researchers led by the University of Adelaide,
suggest a change in climate is the likely cause of the mysterious
disappearance of ancient lions and bears from parts of North America
for a thousand years or more prior to the last Ice Age.


==========================================================================
In a study in Molecular Ecology, the researchers sequenced DNA from
fossils of cave lions and bears from North America and Eurasia to
better understand the timing and drivers of their past movement between continents.

Co-author, Dr Kieren Mitchell from the University of Adelaide's Australian Centre for Ancient DNA said, "There's a common perception that outside
of mass extinctions or direct human interference, ecosystems tend to
remain stable over thousands or even millions of years.

"As illustrated by our study of the fossil record, that's not necessarily
the case.

"Previous research has shown that brown bears (or grizzly bears)
disappeared from some parts of North America for thousands of years
prior to the last Ice Age. They later reappeared, walking from Russia
to Alaska across the Bering Land Bridge -- possibly at the same time as
people moved across the Bridge into North America too.

"But no-one knows exactly why they disappeared in the first place,
which is why studying this event is important." A key finding of the
new research is that cave lions from the same area became extinct more
than once -- before their final extinction they also disappeared and
reappeared thousands of years later, around the same time as bears. There
is no evidence that people caused these temporary disappearances, and
cold Ice Age conditions were not to blame.



========================================================================== "Instead, it looks like a smoking gun pointing to some kind of change
in their ecosystem," Dr Mitchell said.

The timing of lions and bear extinction from parts of North America (specifically Alaska and the Yukon Territory) coincides with evidence
of widespread vegetation change in the region. The researchers suggest
that warm temperatures before the last Ice Age may have caused a change
in the abundance of different kinds of plants, which had knock-on effects
on herbivores and then their predators (like bears and lions).

Colder temperatures leading up to the last Ice Age might have reversed
this change and made the area more hospitable for herbivores, and in
turn their predators.

"Overall, these findings demonstrate just how changeable past ecosystems
have been, and also how the abundance of different species can be very sensitive to changes in climate," Dr Mitchell said.

Lead author from the University of Adelaide Dr Alexander Salis said:
"The shared patterns of dispersal between lions and bears correspond
with the presence of the Bering Land Bridge that connected Russia and
Alaska during Ice Ages.

"The Bridge was periodically exposed and inundated by changing sea levels during the last few Ice Ages, allowing intermittent dispersal of animals
and people between continents and changing the faunal composition.

"While many might think that species arrive in a region and
stay put, we show that the past was much more dynamic, involving
multiple waves of dispersal and local extinctions in this case." ========================================================================== Story Source: Materials provided by University_of_Adelaide. Original
written by Kelly Brown.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Alexander T. Salis, Sarah C. E. Bray, Michael S. Y. Lee, Holly
Heiniger,
Ross Barnett, James A. Burns, Vladimir Doronichev, Daryl Fedje,
Liubov Golovanova, C. Richard Harington, Bryan Hockett, Pavel
Kosintsev, Xulong Lai, Quentin Mackie, Sergei Vasiliev, Jacobo
Weinstock, Nobuyuki Yamaguchi, Julie A Meachen, Alan Cooper,
Kieren J. Mitchell. Lions and brown bears colonized North America
in multiple synchronous waves of dispersal across the Bering Land
Bridge. Molecular Ecology, 2021; DOI: 10.1111/mec.16267 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220104102633.htm
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