Population Structure and diversifying selection in the Netherlands

[Angela]

See:

http://www.tweelingenregister.org/f...NTR-publicaties_2013/Abdellaoui_EJHG_2013.pdf

I'm never sure about this. They see a north south cline, with the population movement going south to north. How do they know the "selection" isn't just because a subset of the main population went north?

"Genetic variation in a population can be summarized through principal component analysis (PCA) on genome-wide data. PCsderived from such analyses are valuable for genetic association studies, where they can correct for population stratification. Weinvestigated how to capture the genetic population structure in a well-characterized sample from the Netherlands and in aworldwide data set and examined whether (1) removing long-range linkage disequilibrium (LD) regions and LD-based SNPpruning significantly improves correlations between PCs and geography and (2) whether genetic differentiation may have beeninfluenced by migration and/or selection. In the Netherlands, three PCs showed significant correlations with geography,distinguishing between: (1) North and South; (2) East and West; and (3) the middle-band and the rest of the country. The thirdPC only emerged with minimized LD, which also significantly increased correlations with geography for the other two PCs. Inaddition to geography, the Dutch North–South PC showed correlations with genome-wide homozygosity (r ¼ 0.245), which mayreflect a serial-founder effect due to northwards migration, and also with height (#: r ¼ 0.142, ~: r ¼ 0.153). The divergencebetween subpopulations identified by PCs is partly driven by selection pressures. The first three PCs showed significant signalsfor diversifying selection (545 SNPs - the majority within 184 genes). The strongest signal was observed between North andSouth for the functional SNP in HERC2 that determines human blue/brown eye color. Thus, this study demonstrates how toincrease ancestry signals in a relatively homogeneous population and how those signals can reveal evolutionary history."

 

[Northener]

I'm never sure about this. They see a north south cline, with the population movement going south to north. How do they know the "selection" isn't just because a subset of the main population went north?

Basically the North-South division in genetic sense is due to a kind of geographic difference, Northeastern Netherlands are connected to the North European Plain, so to North(west) Germany and Southwest Dutch more to the Central-West European area, so closer to Belgium, West Germany, Northern France.

This is a picture of H. Fokkens about the Bronze Age in the Netherlands:

This is even before the Bronze Age and afterwards a more or less consistent division.
The picture that belongs to your linked research gives a striking resembling picture. The Bronze age picture and the nowadays genetic picture is almost 1:1.

North Dutch shares with the North European Plain (and mostly not with the South Dutch):
- Ertebølle (HG culture)
- Funnelbeaker (TRB, neolithic)
- Single grave (Corded Ware)
- North West Bell Beaker
- EBA/ Sögel Wohlde Kreis
- MBA/LBA Elp culture
- Harpstedt-Nienburg Group (Iron Age)
- An 'Anglo-Saxon' influx during migration time.

This gives a differentiated genetics from the area below the Rhine.

This is confirmed by a research of Oscar Lao (2013)