X-chromosome SNP analyses in 11 human Mediterranean populations show a high overall

[Samnium]

homogeneity except in North-west Africans (Moroccans)


Old study but very interesting.

https://bmcevolbiol.biomedcentral.com/articles/10.1186/1471-2148-8-75

[Samnium]

What interested me the most were the differences between Reggio Calabria and Cosenza that are two regions of the same region. It's quite stunning.

In Figure 1a (https://bmcevolbiol.biomedcentral.com/articles/10.1186/1471-2148-8-75#Fig1), the first two axes accounted for 39% of the total variability (first axis: 25%, second axis: 14%). Thus, the Mediterranean populations are quite homogeneous. Equivalently to the results of the AMOVA analysis, the Moroccan population was considerably displaced in the first axis, and the Majorcans were placed in the opposite direction. In the second axis, the differentiation was less, but it is interesting that the Cosenza and Ibiza populations were located opposite to their neighbouring populations (i.e. Catanzaro and Valencia, respectively).


https://media.springernature.com/lw685/springer-static/image/art%3A10.1186%2F1471-2148-8-75/MediaObjects/12862_2007_Article_644_Fig1_HTML.jpg
(Cosenza is CSZ, Reggio is RCA)


As we have commented above, relative high genetic distances between neighbouring populations were found between Cosenza and (1) Catanzaro and (2) Reggio di Calabria and between Ibiza and (1) Majorca and (2) Valencia. The results support the hypothesis that the genetic differentiation of the Ibiza and Cosenza populations is a result of their particular demographic histories [15 (https://bmcevolbiol.biomedcentral.com/articles/10.1186/1471-2148-8-75#ref-CR15), 16 (https://bmcevolbiol.biomedcentral.com/articles/10.1186/1471-2148-8-75#ref-CR16), 23 (https://bmcevolbiol.biomedcentral.com/articles/10.1186/1471-2148-8-75#ref-CR23)]. The Moroccan population showed a high level of differentiation in relation to the other populations, even to those that are geographically close to Morocco (Western side of the Mediterranean basin).

...

Tagarelli et al [16 (https://bmcevolbiol.biomedcentral.com/articles/10.1186/1471-2148-8-75#ref-CR16)] described the Calabria province as a collection of many "human genetic isolates". In contrast to Catanzaro and Reggio di Calabria, Cosenza did not suffer destructive telluric events that would have modified its population structure. So, the population heterogeneity inside Cosenza is more patent than in any of the other two populations. This is reflected by the heterogenic distribution of various genetic markers at the coast compared to the internal areas [16 (https://bmcevolbiol.biomedcentral.com/articles/10.1186/1471-2148-8-75#ref-CR16)]. The results obtained with the 25 X-chromosome markers were in agreement with the previous studies. Cosenza showed not just a relatively high genetic differentiation compared to the populations from Catanzaro and Reggio di Calabria but also a certain displacement in relation to other Mediterranean populations.

[Leto]

You probably need to test your mother too, not only yourself :)

[Samnium]

You probably need to test your mother too, not only yourself :)

Phasing is better yes

[Leto]

Phasing is better yes
I don't even mean that. You just seem to be more interested in your Italian side.

[Samnium]

I don't even mean that. You just seem to be more interested in your Italian side.

Yes because I know more or less how my french side would come out while I don't know at all for my italian one.

Also genetics from France is very interesting but Southern Italy had so much different people/conquests and there are lot of very different results.

Everything varies, and each result that you see amaze you more.

[Samnium]

Nassbean would be interested there are some lines about Morocco :


"The analysis of the Mediterranean populations in comparison to the "worldwide" populations showed a clear intermediate position between African and North-European populations with Morocco somewhat closer to the African populations than the other Mediterranean populations. When only the Mediterranean populations were analyzed in a principal coordinate plot, opposite positions of Moroccans and Majorcans were observed (Figure 1). This supports the existence of a north-south gene flow "barrier" in the western part of the Mediterranean area [9, 10].

It could be argued that the genetic differentiation of the Moroccan population was a result of the arab-berber sub-structure of the individuals sampled in this work, but this hypothesis does not seem likely. Several authors [26, 28] reported a high genetic homogeneity between berbers and arabs in NW Africa, so they suggested that the Arabisation of this area was probably a cultural phenomenon, which did not imply a replacement of the ancestry population. Our results give support the hypothesis of an early settlement of NW Africa [26].

The original berber population seem to have received a low genetic influx from the surrounding areas. Different hypothesis have been suggested to explain the genetic differentiation of the Moroccan population. An initial genetic drift [26, 30] could have caused differences in allele frequency distribution that have not been re-established due to a certain level of geographic isolation.

The Strait of Gibraltar has been described by several authors [9, 10] as an important genetic barrier. Even a certain level of genetic exchange probably occurred between NW Africa and the South of the Iberian Peninsula [10, 27, 32, 33], sharp frequency changes have been described in this area [10, 33]. Also the Sahara desert has been suggested as responsible of the genetic isolation of NW African populations from Sub-Saharan populations [30]. There is no consensus about the impact of the Neolithic demic diffusion in the Mediterranean area [29, 30, 34]. "