make money online Mapping the Genome: Y-chromosome variation in the Pyrenees

Saturday, October 2, 2010

Y-chromosome variation in the Pyrenees

Below is a map and some interesting results from a y-chromosome study of the Pyrennees
One of the most interesting findings of this study was the
very high frequency of R1b1b2d in all Pyrenean samples
except Cinco Villas. In this last population, R1b1b2d was
just carried by one individual, which in fact agrees fairly well
with the general distribution of the haplogroup in Iberians.
In Europe, the mutation defining the subclade R1b1b2d –
SRY2627 (synonymous of M169) is a relatively rare variant
within R1b1b2, being commonly assumed to be typical of
Iberian populations. Nearly everywhere in the Peninsula it
occurs at 2–7% frequency and up to now the highest values
have been found in the North East corner, namely among
Basques (4–11%, Maca-Meyer et al. 2003, Hurles et al. 1999)
and Catalans (22%, Hurles et al. 1999). Frequencies of 13% in
Jacetania, 18% in Alto Urgel, 19% in Cerda˜na and especially
of 48% in Valle de Ar´an, can be found in nearby regions
which have never been observed before.


Maju said...

You can compare with Adams 2008, which samples Iberia better and also includes Gascons. However he uses an old nomenclature, what makes it a bit difficult to follow.

There are two known "Iberian" subhaplogroups (excluding "private" ones) of what is now called R1b1b2a1a1 (P312) and both are almost only Pyrenean. The rest of Iberia (and a good deal of the Pyrenean gene pool) is almost all R1b1b2a1a1* and nothing is yet known about the downstream structure.

These two Pyrenean clades are b and c (for short): M153 and M167 respectively. Clade b is Basque and Gascon only, while clade c is more generally Pyrenean, particularly common among Catalans and has some milder penetration through Eastern Iberia, specially into the Balearic Islands. It's rare in West Iberia, except in North Portugal.

There are two other known sizable (in fact larger) sublineages of R1b1b2a1a1, but they have a more northernly distribution: towards continental Europe one and the other towards Britain and Ireland specially.

It remains to be known what is the structure of all that R1b1b2a1a2*, that is so common in SW Europe and may include several subhaplogroups. No haplogroup detection study has been done in the region AFAIK since the early 2000s and, unlike NW Europeans, SW Europeans have mostly not spent their money in private DNA testing, so the structure of the haplogroup remains somewhat obscure.

Still it seems pretty clear that the clade has center of gravity by diversity around the Pyrenees, supporting the post-LGM spread hypothesis that was once proposed for all R1b but that should be now revised only for its largest sublineage: R1b1b2a1a1-P312.

I posted something on this recently, on Myres 2010, with some cool maps but not dealing with the SW-specific subclades, that Myres prefers to ignore.

Maju said...

Darn nomenclature! Erratum:

Where it reads R1b1b2a1a1 should read R1b1b2a1a2

R1b1b2a1a1 is another clade, second largest, restricted to Central and NW Europe.

Anonymous said...

Here's the odd thing I find with the Val d'Aran. First, it's considered an isolated valley and hence could be a region where a founder effect occurred for SRY2627. But yet, the nearby valleys such as Luchon or the valleys of the Couserans to the north of it do not exhibit higher numbers. Also the valleys such as Val d'Aneu and other valleys in Pallars Sobira or Alt Ribagorcana fail to show the high frequencies. Add in that Catalonia is a fairly mountainous region and the Val d'Aran acted as a sort of gateway to to the Iberian Peninsula but it's not the only Pryenean Valley that provides a gateway. I can think of many others some bigger some smaller, and yet they don't post the bigger percentage. The other issue is diversity, Val d'Aran does not exhibit high diversity from what I'm being informed over at DNA-Forums. In other words, what is found in Germany in variance is basically SRY2627+ emerged there (approximately). Does the Val d'Aran exhibit low diversity and variance in comparison to German SRY2627+ people??