I forget where I saw this but DNA was done on some bees in Canada I believe . Found 2 percent African DNA . Theory was southern sourced bees brought it up there . So yes it has trickled into the gene pool . No one noticed if they are not mean . Even the best bloodlines are mutts . Mutts are good . Too bad the Caucasian bees are hard to find in the USA . They were the gentlest they say . Some of the first Russian imports were said to be mean . They claim they selected away from that trait .
I'd seen some videos of Youtube videos where a guy shows off a really, really mean riled up Russian hive.
But I've also seen some videos where people show how they are manageable and how much they love their Russian bees, and what great honey producers they are.
I find myself pretty curious to try them actually.
I've heard that in Europe people can get Caucasian bees pretty easy and they have some pure Carniolan strains too...just there's that problem with the whole rules against importing them.
There was a lady dr. researcher on bees that was doing a pure Carni strain project in the US also but I forgot her name.
Its interesting to think about all of this.