You can see in this table the degree of genetic diversity for each population.
The 'self' column shows the number of shared IBD ("identical by descent") blocks with other individuals of that country. The 'other' column compares IBD blocks with other countries. The higher the value the more recent the common shared ancestry. The Italians have the lowest self value (0.6), followed by the French (0.7) then the Belgians, Germans and Swiss (all 1.1). These are Europe's most genetically diverse populations according to this study. This coroborates my own
research on surname diversity, which I found to be the highest in Italy, then France, then Belgium.
I'm sorry because it is on the merge of this topic -
but concernng frequence of patronymic surnames, even if your remark keeps a lot of sense, I precise that the density of different surnames in a population depends on more than 1 fact: the date of first patronymic fixed transmission and the research of originality or differenciation for names:
we could wait a less variated panel or surnames if they were fixed in ancient time in a small population - but
Wales chosen patronymic system only about the XIX° century which doesn' t explain the paucity if it explainsthe anglo-norman look of the more born welsh surnames; by the way: the same late (around 1800) date for Jews in France (Napoleon the 1st) - Scandinavia too - we could wait more variated surnames in these cases: not at all: the welsh and scandinavian system was a true patronymic UNfixed one, changing at every generation: son of ... was the rule ('mab' >> '(a)b/p'-+ christian name' in Wales, dropped very often after, and christian name'-sson'-'sen' among Scandinavians: poor enough result too in North Europe -
Spain and Portugal, highly variable region according to this survey, is poor enough concerning surnames too-
other detail: France is vaste: if you study the surnames by regions, you find less variability in ancient times - and when making this kind of statistic, it is difficult to manage the regional forms of same meaning surnames...
concerning the present topic, even if things seem evident enough, I wait having understood the all method before saying my point of view - because I try to tell the impact of population dimension on ancient mixtures from the impact of new mixtures -
sun is came back in Brittany and perhaps elsewhere: surely it will help us to see more clearly?