I was also surprised because I have a pretty extensive genealogy of my wife's side of the family and there's no ancestor from Ireland. Her grandparents—the aunt's parents—have typically Scottish surnames and they are the product of several generations of Scottish ancestors from a small community in Eastern Ontario.
I know of all the ancestors of the aunt (and my wife's mother) for five generations. That's 32 ancestors—their great-great-great-grandparents (Ms. Sandwalk's great4-grandparents). There were four ancestors born in England and 28 born in Scotland, mostly around Glasgow. The original settlers of this district all came from Scotland. That means that to a first approximation about 87% of the aunt's DNA comes from Scotland.
No ancestor was from Ireland.
Looks a bit strange, doesn't it?
Here's the Ancestry.com description of what they mean when they say your DNA is from Ireland.
IrelandIt seems pretty clear that when they say "Ireland" they really mean "Celtic."
Primarily located in: Ireland, Wales, Scotland
Also found in: France, England
Ireland is located in the eastern part of the North Atlantic Ocean, directly west of Great Britain. A variety of internal and external influences have shaped Ireland as we know it today. Ireland’s modern cultural remains deeply rooted in the Celtic culture that spread across much of Central Europe and into the British Isles. Along with Wales, Scotland, and a handful of other isolated communities within the British Isles, Ireland remains one of the last holdouts of the ancient Celtic languages that were once spoken throughout much of Western Europe. And though closely tied to Great Britain, both geographically and historically, the Irish have fiercely maintained their unique character through the centuries.
What does our DNA tell us about being Irish? and found this chart (left) of "the average amount of estimated Irish ethnicity among individuals born in each region of Ireland, England, Scotland, and Wales.
Isn't it strange to refer to people from Scotland with Celtic ancestry as "Irish"?
Look at the table below showing the average "Irish" ethnicity in various locales throughout the British Isles. If you are from Scotland then you probably have about 40% Irish DNA!
That's nonsense. You don't become Irish just because you have Celtic DNA in your genome.
Recall that about 87% of the aunt's DNA was from Scottish ancestors. Most of them were from Southern Scotland where there's about 47% "Irish" haplotypes. Thus, my wife's aunt should have about 0.47 ×: 87% = 41%
Lots of people who had their DNA tested by Ancestry.com are as puzzled as we were. There are many forums where the issue is being discussed. See, for example: So am I Irish or Scottish?.
Ancestry.com screwed up. They shouldn't be saying that their client's DNA is 61% "Ireland." They should be saying it's Celtic. There are an awful lot of people like my wife's aunt who don't know how to interpret their "Irish" DNA and they are going to be very confused.
1. 61% Ireland; 24% Europe West; 7% Great Britain; 7% Trace Regions; 1% West Asia.