Ancient genomes suggest woolly rhinos went extinct due to climate
change, not overhunting

Date:
August 13, 2020
Source:
Cell Press
Summary:
Although overhunting led to the demise of some prehistoric megafauna
after the last ice age, a new study found that the extinction of
the woolly rhinoceros may have been caused by climate change. By
sequencing ancient DNA from 14 woolly rhinos, researchers found
that their population remained stable and diverse until only a few
thousand years before it disappeared from Siberia, when temperatures
likely rose too high.



FULL STORY ========================================================================== [Woolly rhinoceros | Credit: (c) auntspray / stock.adobe.com] Woolly
rhinoceros illustration (stock image).

Credit: (c) auntspray / stock.adobe.com [Woolly rhinoceros | Credit: (c) auntspray / stock.adobe.com] Woolly rhinoceros illustration (stock image).

Credit: (c) auntspray / stock.adobe.com Close The extinction of
prehistoric megafauna like the woolly mammoth, cave lion, and woolly
rhinoceros at the end of the last ice age has often been attributed to
the spread of early humans across the globe. Although overhunting led to
the demise of some species, a study appearing August 13 in the journal
Current Biology found that the extinction of the woolly rhinoceros may
have had a different cause: climate change. By sequencing ancient DNA from
14 of these megaherbivores, researchers found that the woolly rhinoceros population remained stable and diverse until only a few thousand years
before it disappeared from Siberia, when temperatures likely rose too
high for the cold- adapted species.


==========================================================================
"It was initially thought that humans appeared in northeastern Siberia
fourteen or fifteen thousand years ago, around when the woolly rhinoceros
went extinct.

But recently, there have been several discoveries of much older human occupation sites, the most famous of which is around thirty thousand
years old," says senior author Love Dale'n, a professor of evolutionary genetics at the Centre for Palaeogenetics, a joint venture between
Stockholm University and the Swedish Museum of Natural History. "So,
the decline towards extinction of the woolly rhinoceros doesn't coincide
so much with the first appearance of humans in the region. If anything,
we actually see something looking a bit like an increase in population
size during this period." To learn about the size and stability of the
woolly rhinoceros population in Siberia, the researchers studied the
DNA from tissue, bone, and hair samples of 14 individuals. "We sequenced
a complete nuclear genome to look back in time and estimate population
sizes, and we also sequenced fourteen mitochondrial genomes to estimate
the female effective population sizes," says co-first author Edana Lord,
a PhD student at the Centre for Palaeogenetics.

By looking at the heterozygosity, or genetic diversity, of these genomes,
the researchers were able to estimate the woolly rhino populations for
tens of thousands of years before their extinction. "We examined changes
in population size and estimated inbreeding," says co-first author Nicolas Dussex, a postdoctoral researcher at the Centre for Palaeogenetics. "We
found that after an increase in population size at the start of a cold
period some 29,000 years ago, the woolly rhino population size remained constant and that at this time, inbreeding was low." This stability
lasted until well after humans began living in Siberia, contrasting the declines that would be expected if the woolly rhinos went extinct due to hunting. "That's the interesting thing," says Lord. "We actually don't
see a decrease in population size after 29,000 years ago. The data we
looked at only goes up to 18,500 years ago, which is approximately 4,500
years before their extinction, so it implies that they declined sometime
in that gap." The DNA data also revealed genetic mutations that helped
the woolly rhinoceros adapt to colder weather. One of these mutations,
a type of receptor in the skin for sensing warm and cold temperatures,
has also been found in woolly mammoths.

Adaptations like this suggest the woolly rhinoceros, which was
particularly suited to the frigid northeast Siberian climate, may
have declined due to the heat of a brief warming period, known as the Bo/lling-Allero/d interstadial, that coincided with their extinction
towards the end of the last ice age.

"We're coming away from the idea of humans taking over everything as soon
as they come into an environment, and instead elucidating the role of
climate in megafaunal extinctions," says Lord. "Although we can't rule out human involvement, we suggest that the woolly rhinoceros' extinction was
more likely related to climate." The researchers hope to study the DNA
of additional woolly rhinoceroses that lived in that crucial 4,500-year
gap between the last genome they sequenced and their extinction. "What we
want to do now is to try to get more genome sequences from rhinos that
are between eighteen and fourteen thousand years old, because at some
point, surely they must decline," says Dale'n. The researchers are also
looking at other cold-adapted megafauna to see what further effects the warming, unstable climate had. "We know the climate changed a lot, but the question is: how much were different animals affected, and what do they
have in common?" This work was supported by FORMAS, the Swiss National
Science Foundation, the Carl Tryggers Foundation, the European Research
Council Consolidator Award, and the Knut and Alice Wallenberg Foundation.


========================================================================== Story Source: Materials provided by Cell_Press. Note: Content may be
edited for style and length.


========================================================================== Journal Reference:
1. Edana Lord, Nicolas Dussex, Marcin Kierczak, David Di'ez-del-Molino,
Oliver A. Ryder, David W.G. Stanton, M. Thomas P. Gilbert, Fa'tima
Sa'nchez-Barreiro, Guojie Zhang, Mikkel-Holger S. Sinding, Eline D.

Lorenzen, Eske Willerslev, Albert Protopopov, Fedor Shidlovskiy,
Sergey Fedorov, Herve' Bocherens, Senthilvel K.S.S. Nathan,
Benoit Goossens, Johannes van der Plicht, Yvonne L. Chan, Stefan
Prost, Olga Potapova, Irina Kirillova, Adrian M. Lister, Peter
D. Heintzman, Joshua D. Kapp, Beth Shapiro, Sergey Vartanyan,
Anders Go"therstro"m, Love Dale'n. Pre- extinction Demographic
Stability and Genomic Signatures of Adaptation in the Woolly
Rhinoceros. Current Biology, 2020; DOI: 10.1016/ j.cub.2020.07.046 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200813113157.htm

--- up 4 weeks, 1 day, 1 hour, 55 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)