I'd say that the correlation between the map and that historical text is striking.
I would not call it as striking, yet interesting and nothing more.
Those who create maps about 'White Croatia' use the only source they have about it but decide to improvise and place it in Poland, in spite of what the text says.
The vagueness of location of White Croatia and White Croats produced substantive debate by historians. As there's an issue whether existed political entity called as White Croatia or Croatia in that part of Europe prior or after the 7th century, the focus switched from White Croatia to tribes of White Croats who were mostly mentioned from Bohemia, Southern Poland, Galicia to Western Ukraine rather than in Bavaria i.e. Germany.
The highland groups living there Boykos, Lemkos, Hutsuls... De Administrando Imperio that the Serbs called their former land "Boyka".
According to
De Administrando Imperio the Serbs former land was called as Boïki and usually, it is translated as Bohemia or etymologically related to the name of Celtic tribe Boii who lived in Bohemia and Bavaria, meaning west of White Croatia and Croats. Actually, as far I know, all other historical sources place Serbs, Sorbs, Servians west of Croats somewhere near or within Bavaria, and do not mention them in the east. This means that by location Boykos, Lemkos and Hutsuls could be related to White Croats and hence contemporary Croats, but can not be with Serbs whose ancestors should be Sorbs in Bavaria.
1.How then you connect exclusively R1a or I2a1 with either population be them Serbs or Croats?
2.Were they genetically pure of R1a or I2a1 din?
3.What genetic material they brought to Balkans then?
4.Then the obvious question to the "migrations model" what was their number or genetic impact ?
1. There can not be made any exclusive connection between these haplogroups and populations
2. No
3. - 4. Depends whether those Croatian and Serbian tribes were or were not only elite tribes who managed or not to have many descendants, i.e. were in small number as mostly it is speculated they came in a smaller second wave migration dated to the 7th century (after first Slavs started to arrive already in the 6th century) and managed to impose political rule in the Western Balkan. Actually, if we are going to keep
De Administrando Imperio by word, those migrant Serbs soon scattered around and their principality became depopulated due to war with Bulgars. In other words, a similar thing happened to Bulgars themselves - they were political elite in Bulgaria whose identity and descendants over the centuries vanished, being replaced by Slavic Bulgarians. They kept their name, but the people behind that were not Bulgars anymore. The similar thing could have happened to both Serbs and Croats. Hence, currently speculating on genetic material without broader perspective could be misleading.
mtDNA: according to Nikitin et al. 2009 and mtDNA analysis on Boykos, Lemkos and Hutsuls; Boykos had much lower frequency of hg-H, lower hg-J, but similar hg-U like mainland Croats from Croatia, Lemkos also had lower hg-H, similar hg-J and hg-U, and had high hg-I frequency like at island of Krk (c. 11%) implying local founder effect, Hutsuls very similar hg-H, similar hg-J, but lower hg-U. Overall, the Hutsuls were closest to mainland Croats from Croatia. However, they could not be so close to subclade frequency (particularly hg-H, as Croats have lower H1), and it is doubtful the percent of women among those migrant early Serbs and Croats.
Y-DNA: if, as according to Shetop, the subclade of R-M558 (R-CTS1211)
was the predominant haplogroup of early Croats and not I-PH908, then it is ridiculous to consider that I-PH908
was the predominant haplogroup of early Serbs, and not some R1a subclade, as according to Behar et al. 2003, the Sorbs have over 63% of R1a1, the highest percent in Europe. Is it not "predominant" enough?
Also I found it odd to connect that Serbs and as well as Croats were migrating hand in hand. These theories arosed in the 19th century when the idea of Yugoslavia was being set up.
Once again, if we keep
De Administrando Imperio by word then it is literally stated that the Croats came before the Serbs. However, they migrated in a similar period, probably during Samo's union (631–658) when was open border from river Elbe (Germany) in the north up to the region of Carniola (Slovenia) in the south, i.e. border with the province of Dalmatia.