I would say that the pesticide immunity genes arise because of evolutionary selection, but once they come into existance commercial beekeeping practices quickly spread those genes from hive to hive and across the country.
You might be right that the physical distribution plays a role, but the partial selective pressure of insecticide is like a resistance-generating machine -- as anyone who has tried to kill cockroaches will tell you.
Regardless, I think we both agree that the extremely unnatural pressures of industrial agriculture are a root
cause here.
For example, Scandinavian countries that have made a concerted effort to only prescribe antibiotics to humans when they are medically necessary saw the genes for antibiotic resistance becoming less prevalent.
Unfortunately, America still allows agribusiness to feed livestock a constant stream of lower dose antibiotics, because doing so makes animals more efficient at turning feed into muscle.
I'm more interested in no longer spreading the mite gene(s) for pesticide immunity across the country.