More on Finnish population substructure

There's a new paper in the American Journal of Human Genetics following on from the paper on the genetics of metabolic traits that I posted on earlier in the week. This study explicitly focuses on the population structure of the Finns, and includes these maps showing the correlation between geography and genetics within Finland and related populations:
(Image from Jakkula et al. (2008) The Genome-wide Patterns of Variation Expose Significant Substructure in a Founder Population The American Journal of Human Genetics, 83 (6), 787-794 DOI: 10.1016/j.ajhg.2008.11.005)

More details below the fold...

The real addition to these maps relative to the ones I showed in my last post is inclusion of extra Finnish regions (including the capital, Helsinki) as well as two external populations: the HapMap "individuals of northern and western European origin from Utah" (CEU) samples, and a collection of Swedish individuals with no information about location of ancestry. The cluster chart at the top shows all of these populations, while the chart at the bottom right shows only the Finnish isolates (excluding Helsinki).

The obvious findings: Finnish groups cluster separately from both neighbouring Swedish and more distant European populations; and Finnish population structure is far more apparent in northern regions than in the south. This latter finding presumably reflects recent founder effects and stronger isolation between northern populations compared to the comparatively older, more urbanised southern populations. The mixing effect of urbanisation (pointed out by Bob O'H in a recent comments thread) is particularly clear in the Helsinki samples, who have ancestry derived from a wide geographical region.

The new paper has much more detail that I don't have time to get stuck into now, but feel free to add your own thoughts in the comments. I'll leave you with this graph showing three measures of inbreeding (related to lengths of homozygosity, for those interested) in the various populations, coloured as in the figure above:

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It would be interesting if they could add data from northern Sweden and Russian Karelia.

Someone else can correct me, but I'm not sure the southern population is more urbanzed per se (Ha! I love using that phrase when discussing Finland): it was still very rural, but with urban pockets (e.g. Helsinki and Tampere), and the sampling was carried out to try and get a structure that pre-dated indutrialisation. This might also bias the sample towards rural populations.

I bumped into a friend on the bus today, and he was telling me some interesting stuff: it seems that there's more to the Finnish story than we have here.