These "refugia" are where the Ice Age European people were driven during periods of peak glaciation. There are 3 such "refugia" in the Western Mediterranean and the people whose ancestors lived there have differences from the others.
The Ice Age was tough on the Europeans!
Sure was. Britain has had multiple attempts by humans or ancestors to colonize the place, all previous attempts being unsuccessful. For the life of me I can't understand why Europeans are obsessed with trying to bring on another glacial age. Of course, IMHO, humans don't have the ability to significantly influence climate, so they won't succeed. Another is inevitable, eventually, though.
The Ice Age was tough on the Europeans! ................. It may be true about most of them, but, it had no effect on those of us who migrated here on the Great Ice Ship. LOL