Genetic borders in Europe

[Peterski]

Here is my PCA with regional averages, probably the biggest genetic border that showed up, is this between Slovenia and North-Eastern Italy. Geographically, Veneto-Friuli and Slovenia are neighbours, but in terms of DNA there is a big distance between them.

Any ideas on why is this the case?: https://i.imgur.com/Z3NrUkn.png

https://i.imgur.com/Z3NrUkn.png