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Ancestry of polar bears traced to Ireland
Penn State ^ | July 7, 2011 | Unknown

Posted on 07/07/2011 12:36:25 PM PDT by decimon

An international team of scientists has discovered that the female ancestor of all living polar bears was a brown bear that lived in the vicinity of present-day Britain and Ireland just prior to the peak of the last ice age -- 20,000 to 50,000 years ago. Beth Shapiro, the Shaffer Associate Professor of Biology at Penn State University and one of the team's leaders, explained that climate changes affecting the North Atlantic ice sheet probably gave rise to periodic overlaps in bear habitats. These overlaps then led to hybridization, or interbreeding -- an event that caused maternal DNA from brown bears to be introduced into polar bears. The research, which is led by Shapiro and Daniel Bradley of Trinity College Dublin, is expected to help guide future conservation efforts for polar bears, which are listed as threatened under the Endangered Species Act. The results of the study will be published on 7 July 2011 in the journal Current Biology.

Polar and brown bears are vastly different species in terms of body size, skin and coat color, fur type, tooth structure, and many other physical features. Behaviorally, they are also quite distinct: Polar bears are expert swimmers that have adapted to a highly specialized, arctic lifestyle, while brown bears -- a species that includes Grizzlies and Kodiaks -- are climbers that prefer the mountain forests, wilderness regions, and river valleys of Europe, Asia, and North America. "Despite these differences, we know that the two species have interbred opportunistically and probably on many occasions during the last 100,000 years," Shapiro said. "Most importantly, previous research has indicated that the brown bear contributed genetic material to the polar bear's mitochondrial lineage -- the maternal part of the genome, or the DNA that is passed exclusively from mothers to offspring. But, until now, it was unclear just when modern polar bears acquired their mitochondrial genome in its present form."

Although previous researchers had suggested that the ancient female ancestor of modern polar bears lived on the ABC Islands -- the Alaskan islands of Admiralty, Baranof, and Chichagof -- only 14,000 years ago, Shapiro's team found evidence of a much earlier hybridization event. Because of this event, the modern polar bear's mitochondrial DNA probably underwent fixation -- a drastic reduction in genetic variation and a transition to a state in which the entire gene pool includes only one form of a particular gene. After performing genetic analyses of 242 brown-bear and polar-bear mitochondrial lineages sampled throughout the last 120,000 years and across multiple geographic ranges, Shapiro's team found that the fixation of the mitochondrial genome likely occurred during or just before the peak of the last ice age, possibly as early as 50,000 years ago, near present-day Ireland. Shapiro noted that the specific population of brown bears that shared its maternal DNA with polar bears has been extinct for roughly 9,000 years. However, her data offer clear genetic evidence that the two species were in contact long before the brown bear's disappearance from the British Isles.

Shapiro explained that, although both polar bears and brown bears have experienced long periods of geographic stability, episodes of both warming and cooling during the last 500,000 years or more likely led to environmental conditions favorable to hybridization between the two bear species. "Polar and brown bears likely came into contact intermittently, in particular in coastal regions where the effects of climate change may have been more pronounced," Shapiro said. "Whenever they come into contact, there seems to be little barrier to their mating."

Such climate changes, Shapiro said, included vast fluctuations in the amount and distribution of habitats in the North Atlantic region. These fluctuations would have caused the geographic ranges of polar and brown bears to overlap temporarily. For example, during a warming period, elevated air temperatures, melting glacial ice, and rising sea levels likely forced polar bears to spend more time onshore in search of food, and thus closer to their brown-bear neighbors. Likewise, during a cooling glacial period, brown bears living farther from the coast may have been forced into habitat normally occupied by polar bears. The British-Irish Ice Sheet reached its maximum extent about 20,000 years ago, with major tidewater glaciers on the western shelf and down the Irish Sea Basin into the Celtic Sea. During this period, parts of Ireland were probably uninhabitable because of glaciation, pushing brown bears toward ice shelves and land exposed by lower sea levels. "The bottom line is that the two species bumped up against one another for extended periods of time on different occasions, sharing both habitats and genes," Shapiro said.

Climatological data suggest that the planet now is experiencing another warming period -- known as the Holocene or the Present Interglacial -- which is even warmer than the period that marked the beginning of the last ice age. "Interestingly, today we are seeing a similar change in the arctic climate, with melting glacial ice, fewer sea-ice days, longer open-water periods during summer, and rising sea levels," Shapiro said. "And once again that change is providing polar and brown bears the opportunity to share habitats and to hybridize. In fact, several adult hybrid bears have been reported in the last five years." For this reason, Shapiro said, scientists should reconsider conservation efforts focused not just on polar bears, but also on hybrids, since hybrids may play an underappreciated role in the survival of certain species. She added that a thorough understanding of the polar bear's deep genetic history and its response to previous environmental changes could help to inform conservation strategies for the dwindling population of polar bears today.

Shapiro hopes to design future studies of the polar bear's DNA by concentrating on other parts of the animal's genome. "Until now we have focused our efforts on the polar bear's mitochondrial DNA, which traces only the mother's side of the family tree," Shapiro said. "But there is much to be learned from the nuclear genome -- the genetic material contained within the nucleus of the cell, which has been passed to offspring from both mothers and fathers." Shapiro said that a more complete investigation of this part of the genetic story could answer deeper questions about how interactions with other species and environmental changes affected the polar bear in the distant past, how frequently hybridizations between species actually happened, and how these hybridizations affected the genetic diversity of the polar bear generally.

###

In addition to Shapiro and Bradley, other researchers who contributed to the study include Tara L. Fulton at Penn State and scientists at universities and institutions in California, Ireland, the United Kingdom, Belgium, Spain, Denmark, Russia, and Sweden. The sequencing of ancient Irish and British bears was carried out by Ceiridwen Edwards at Trinity College Dublin, where the unprecedented similarity with polar bears was first noted.

Funding for the research was provided by the European Research Council; the National Evolutionary Synthesis Center (NESCent); the Irish Council for Science, Engineering, and Technology; and the U.S. National Science Foundation.

[ Katrina Voss ]

CONTACTS

Beth Shapiro: 814-321-8389, beth.shapiro@gmail.com PLEASE NOTE: Dr. Shapiro will be traveling in China and Indonesia through 18 July and is likely to have some access to email during this trip. She will do her best to respond to phone inquiries, as well (+353 1 896 1088) but requests that you be mindful of the time difference. Daniel Bradley: +353 1 896 1088, dbradley@tcd.ie Mark Thomas: +44 (0)20 7679-2286, m.thomas@ucl.ac.uk Barbara Kennedy (PIO): 814-863-4682, science@psu.edu

IMAGES High-resolution images associated with this research are online at http://www.science.psu.edu/news-and-events/2011-news/Shapiro6-2011, which is where text will be posted after the embargo lifts.


TOPICS: History; Pets/Animals
KEYWORDS: acrossatlanticice; ancestry; bear; bears; brucebradley; catastrophism; climate; dennisstanford; godsgravesglyphs; ireland; littleiceage; polar; polarbear; polarbears; solutreans; traced
But don't fall for that "Kiss me, I'm Irish!" ruse.
1 posted on 07/07/2011 12:36:29 PM PDT by decimon
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To: SunkenCiv

Ping


2 posted on 07/07/2011 12:38:04 PM PDT by decimon
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To: decimon

Ancestry of polar bears traced to Ireland

... this explains the whole “river dance” thing you can sometimes see on icebergs.


3 posted on 07/07/2011 12:39:27 PM PDT by aMorePerfectUnion (This message carfully checkd to misteakes by powerful softwhere)
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To: decimon
She added that a thorough understanding of the polar bear's deep genetic history and its response to previous environmental changes could help to inform conservation strategies for the dwindling population of polar bears today.

Except that the population isn't dwindling. They just THINK it might in the future.

4 posted on 07/07/2011 12:42:17 PM PDT by dirtboy
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To: decimon

Now thats some good science fiction..
Clan of the Irish Bear... all it needs is a buxom Cave Sheila..


5 posted on 07/07/2011 12:44:27 PM PDT by hosepipe (This propaganda has been edited to include some fully orbed hyperbole...)
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To: decimon
Well, I guess this is finally explained:


6 posted on 07/07/2011 12:44:35 PM PDT by dirtboy
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To: decimon

I think we need Al Gore here to straighten this all out.


7 posted on 07/07/2011 12:47:46 PM PDT by donhunt (I am sick and tired of those bastards insulting and lying to me.)
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To: decimon

Isn’t Penn State still harboring that scientist that falsified the “Global Warming” evidence? Take anything from this ‘university’ with grain of salt... unless it’s a football score.


8 posted on 07/07/2011 12:50:22 PM PDT by Tallguy (You can safely ignore anything that precedes the word "But"...)
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To: dirtboy

Indeed...


9 posted on 07/07/2011 12:51:41 PM PDT by WayneS ("I hope you know this will go down on your PERMANENT record...")
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To: decimon

If polar bears came from Ireland, they would still have a green hue (sheesh... don’t these scientist ever THINK). The exception would be the protestant polar bears... they would be orange. The green polar bears and orange polar bears would fight all the time. Aren’t you glad that I settled this debate? /s


10 posted on 07/07/2011 12:58:14 PM PDT by momtothree
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To: decimon

This might explain the fertile hybrids that occur occasionally.


11 posted on 07/07/2011 12:58:27 PM PDT by dog breath
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To: decimon
Beth Shapiro, the Shaffer Associate Professor of Biology at Penn State University and one of the team's leaders, explained that climate changes affecting the North Atlantic ice sheet probably gave rise to periodic overlaps in bear habitats.

What?

There were climate changes in the past?

The polar ice caps melted in the past?

How can this be?

They didn't have SUVs or coal-fired power plants back then, did they?

12 posted on 07/07/2011 1:03:46 PM PDT by E. Pluribus Unum ("A society of sheep must in time beget a government of wolves." - Bertrand de Jouvenel des Ursins)
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To: decimon
Photobucket
13 posted on 07/07/2011 1:06:33 PM PDT by SWAMPSNIPER (The Second Amendment, A Matter of Fact, Not a Matter of Opinion)
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To: SWAMPSNIPER

This goes a long way to explain my sudden overpowering urges to dig for grubs under rotting logs.


14 posted on 07/07/2011 1:49:55 PM PDT by Ax
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To: decimon

There is no such thing in my ancestry - grrr.

15 posted on 07/07/2011 2:05:50 PM PDT by frithguild
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To: decimon; StayAt HomeMother; Ernest_at_the_Beach; 1010RD; 21twelve; 24Karet; 2ndDivisionVet; ...

· GGG managers are SunkenCiv, StayAt HomeMother, and Ernest_at_the_Beach ·
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Thanks decimon. To all -- please ping me to other topics which are appropriate for the GGG list.
 

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16 posted on 07/07/2011 6:27:03 PM PDT by SunkenCiv (Yes, as a matter of fact, it is that time again -- https://secure.freerepublic.com/donate/)
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17 posted on 07/07/2011 6:28:54 PM PDT by SunkenCiv (Yes, as a matter of fact, it is that time again -- https://secure.freerepublic.com/donate/)
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To: decimon
"But don't fall for that "Kiss me, I'm Irish!" ruse. "

But, it's true. My DNA proves it.

Ah, come on now, just a little kiss, eh?

18 posted on 07/07/2011 6:30:52 PM PDT by blam
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To: blam
Ah, come on now, just a little kiss, eh?

Not after seeing those pictures of what you did to that seal.

19 posted on 07/07/2011 6:40:46 PM PDT by decimon
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To: decimon; blam; SunkenCiv
Not after seeing those pictures of what you did to that seal

They anything like what those Seals did to that raghead?

20 posted on 07/07/2011 6:58:13 PM PDT by bigheadfred (Beat me, Bite me, Make Me write Bad Checks)
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To: SunkenCiv

Wish I was better at photoshop. I’d switch that Coke bottle in the polar bear-Coca Cola ad for a bottle of Bushmills.


21 posted on 07/07/2011 7:02:10 PM PDT by Betis70 (Bruins!)
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To: decimon

“Grizzlies and Kodiaks — are climbers that prefer the mountain forests”

I thought Grizzlies COULDN’T climb trees?


22 posted on 07/07/2011 7:41:34 PM PDT by ZULU (Lindsey Graham is a nanometrical pustule of pusillanimous putrescence)
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To: ZULU
I thought Grizzlies COULDN’T climb trees?

I've read that. But not lately. It seems that they can but I'd think that they probably can't once they reach too great a weight.

23 posted on 07/07/2011 8:06:32 PM PDT by decimon
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To: decimon
Photobucket
24 posted on 07/07/2011 8:35:01 PM PDT by IYellAtMyTV (Je t'aime, faire du bruit comme le cochon.)
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To: decimon

My daughter says there was a green polar bear at the San Diego Zoo not too long ago. Algae had invaded hollow hairs in its fur. Once they figured it out, he had to have a thorough scrub down to get rid of it.


25 posted on 07/07/2011 8:54:36 PM PDT by married21 (As for me and my house, we will serve the Lord.)
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To: married21
Algae had invaded hollow hairs in its fur. Once they figured it out, he had to have a thorough scrub down to get rid of it.

Not my job!

26 posted on 07/07/2011 8:57:36 PM PDT by decimon
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To: married21
"My daughter says there was a green polar bear at the San Diego Zoo not too long ago. Algae had invaded hollow hairs in its fur. Once they figured it out, he had to have a thorough scrub down to get rid of it. "

I think I read something about that too.

Polar bear skin is black and the hair acts like a fiber optic and directs sunlight to the skin.

27 posted on 07/07/2011 10:37:21 PM PDT by blam
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To: decimon
Ancestry of polar bears traced to Ireland
Ah-ha!
So that explains my 'mean streak' (or so I'm told).

[at least I have a valid excuse for it now ;-)]

28 posted on 07/08/2011 4:24:12 AM PDT by Condor51 (The difference between stupidity and genius is that genius has its limits [A.Einstein])
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To: SunkenCiv

Ursa Lucy! The polar bear Eve.


29 posted on 07/08/2011 5:37:37 AM PDT by TheOldLady (FReepmail me to get ON or OFF the ZOT LIGHTNING ping list.)
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To: SunkenCiv

You were out last night messing around with that brown bear, weren't you?!

30 posted on 07/08/2011 12:40:23 PM PDT by colorado tanker
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