I made this PCA-map by using distribution numbers from Eupedia. A small modification was made and Finnish numbers were replaced by the Finnish east-west distribution from the study Lappalainen et al.
Ydna, of course, represents only a small part of the genome. It however moves forward the genetic inheritance without recombination. Recombination is typical for autosomal genes, so the yDna is also free of similar genetic drift. A strong yDna-polarization can’t be completely ignored in estimating the overall homogeneity of populations because it has a connection with the autosomal inheritance through individuals. For example 100 % of men in a population belonging to the same branch of certain haplogroup can have a strong parallel effect on the autosomal side of the genome. In this context don't get confused by terms homogeneity, admix shown by admix-analyses and opposite terms heterozygosity/homozygosity.
We obviously can’t claim that the diversity in yDna means always diversity in auDna, neither claim that homogeneous yDna leads to homogeneous autosomal genes per se, but looking at the history and genetic studies we see certainly the connection between yDna and auDna. This makes the yDna certainly helpful in estimating populational structures. Keeping in mind, however, that when analyses lead to interpretations of history, we should also know something about the history of yDna groups before making conclusions to avoid making circular arguments in evaluating the history. Be careful.
Nevertheless, a strong correlation between yDna and auDna is obvious in this small analysis. I could put comparable autosomal analyses here. Basque, Irish, and certain British people shows homogeneous fractions on yDna, which seems to correlate with the strong own history, thus likely points also to certain homogeneity of these population (Can we accept this by only looking analyses, not based on our foreknowledge?). Also, the Bosnian Croats and the Catalonians belonging to these edging groups sounds acceptable. A thousand dollars questions is whether all Balkans belonging to the HG’s I2+I2a came from Bosnia, whether Brits, Scots and Spaniards belonging to the Hg R1b came from Wales, Basque country and Catalonia, or do we have other explanations. I think that we have, it is genetic isolation and genetic drift of these populations.
Click here to see a big view.