Beekman says "genetic diversity is believed to make the colony more resistant to disease and also allow for worker bees from different fathers, who have different strengths and weaknesses, to have specialized roles in the colony."
I was talking with Alan Buckley in ventrillo the other day about this very thing, and his opinion is that those areas and perhaps states that are not having an issue with CCD are those that more than likely have lots of genetic diversity, as in feral colonies.
We have lots here as some of you know by my posts. Alan said one of the culprits could be inbreeding, it seems Beekman's findings support what Alan is saying.
You know with a name like Beekman, you just have to have something to do with bees, right? ;)