Researchers from the University of Adelaide and elsewhere have sequenced and analyzed mitochondrial DNA from fossils of cave lions (Panthera spp.) and brown bears (Ursus arctos), two megafaunal carnivorans that dispersed from Eurasia into North America through the Pleistocene, to higher perceive the timing and drivers of their previous motion between the continents throughout the Bering Land Bridge. Their outcomes reveal hanging synchronicity within the inhabitants dynamics of Beringian lions and brown bears, with a number of waves of dispersal throughout the Bering Land Bridge. The evolutionary histories of those two megafaunal animals underline the essential biogeographical function of the Bering Land Bridge within the distribution, turnover and upkeep of megafaunal populations in North America.
Cave lions painted within the Chauvet Cave, France.
“The shared patterns of dispersal between lions and bears correspond with the presence of the Bering Land Bridge that connected Siberia and Alaska during ice ages,” mentioned Dr. Alexander Salis, a researcher with the Australian Centre for Ancient DNA on the University of Adelaide.
“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.”
“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,” added Dr. Kieren Mitchell, additionally from the Australian Centre for Ancient DNA on the University of Adelaide.
“As illustrated by our study of the fossil record, that’s not necessarily the case.”
“Previous research has shown that brown bears disappeared from some parts of North America for thousands of years prior to the latest Ice Age.”
“They later reappeared, walking from Siberia 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.”
Among the group’s key findings is that cave lions from the identical space grew to become extinct greater than as soon as — earlier than their last extinction additionally they disappeared and reappeared hundreds of years later, across the similar time as bears.
There isn’t any proof that individuals prompted these non permanent disappearances, and chilly Ice Age situations had been to not blame.
“Instead, it looks like a smoking gun pointing to some kind of change in their ecosystem,” Dr. Mitchell mentioned.
The timing of lions and bear extinction from elements of North America — particularly Alaska and the Yukon Territory — coincides with proof of widespread vegetation change within the area.
The research means that heat temperatures earlier than the Ice Age could have prompted a change within the abundance of various sorts of vegetation, which had knock-on results on herbivores after which their predators (like bears and lions).
Colder temperatures main as much as the Ice Age might need reversed this variation and made the realm extra hospitable for herbivores, and in flip 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 mentioned.
The research seems within the journal Molecular Ecology.
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Alexander T. Salis et al. Lions and brown bears colonized North America in a number of synchronous waves of dispersal throughout the Bering Land Bridge. Molecular Ecology, printed on-line November 8, 2021; doi: 10.1111/mec.16267