There is a new free access paper on Swedish genetic structure:
K. Humphreys et al. The Genetic Structure of the Swedish Population. PLoS ONE, 2011. Open access.
Swedes are not too heterogeneous so this exercise is a bit of applying a microscope. Yet I'd love to see much lower resolution analysis of comparable quality on many other populations of Europe or elsewhere.
Interestingly, the authors took some pains to, first of all, prevent that Finnish ancestry may have distorted the results because:
It may be argued that Finnish ancestry may be responsible for a large portion of the genetic stratification detectable in a Swedish sample but we chose to exclude them as the studies we combined had different inclusion criteria with respect to foreign ancestry.
|Fig S1 - shows the 'uncut' Swedish PC and how the cut was done|
The result of this surgery of sorts is this PCA:
|Fig S3 - PCs by county|
It is very apparent that the Norther Swedish lands, previously detected already as 'different' define PC1, while the isolated mountain county of Dalarna defines PC2.
The impact of these two PCs in the Swedish sample is mapped in fig. 2:
|Fig. 2 - color scale from dark brown to yellow|
It is interesting to notice that the extremes of these two PC polarities may be caused more by their own genetic isolation than anything else, as it's apparent in fig. 5:
|Fig. 5 - Homozygosity (base is Stockholm county)|
Both Finnish and Norwegian samples applied to these two PCs produced negative values (supp. materials), what reinforces this idea that they are a creation of genetic isolation in Sweden and not external influences.
Further PCs (up to PC10) are mapped in fig S7 but I do not see them as very informative, excepting maybe PC6, which shows a pole near the Southern Norwegian border.
See also in this blog: Swedish autosomal genetics.