Nature knows best. But is the nature on mite's side or bee's side - that is the question!
That a great question.
Now if I understand that a queen can get tagged up to forty times, that drones do travel and are not just bound to one hive and do visit other hives in their lives, I guess that where they get the genetic diversity, then nature is on the bee side. If as beeks we stop giving all of the bees crutches in chemical form, then nature will be able to proceed and make bees resistant to whatever natural threat that is out there.
I understand that Acid is found in all hives, albeit in much smaller amounts than after a treatment, whereas powdered sugar is not, so i a way, the sugar is also a crutch.
I actually plan on giving one hive in each of my location absolutely no treatment what so ever...lets see what happens. I expect to loose some over time but I also expect that one will survive more than a couple of years, that would be the one where my future grafting will come from...
But even then, back to genetic diversity, it will not ensure that the queens I get from there will be the same as the mother. Lest I can saturate the area with drones from that hive, even then the probabilities of replicating that queen will be small.
Mites...mate once, maybe more...( don't know too much about the little buggers), lay a few eggs, their genetic diversity is going on at a much slower pace...eventually they will not be as much of a problem.
Fertilizers, pesticides and other man made compounds are a much harder thing to wrestle with.