Re: German Black bees in the Southeastern US actually Apis mellifera iberiensis?
DNA testing with honeybees will only date back so many generations, not hundreds of years. This is because of the diverse mating of drones and queens, also due to the fact that some years, more than one queen uses a hive, mates, absconds, and moves on, then another takes up residence, lays, and if it is a good year, swarms off leaving the new queen in charge.
It takes some very strong isolation to limit the genetic diffusion (think of a drop of red dye spilled into the ocean, in one year it circumnavigates the entire globe), like perhaps honeybees living in Iceland will have some inbred tendencies. Strong selective pressure can change honeybee populations' traits in a hundred years quite drastically. Stable conditions will tend to promote the most favored traits for that set of conditions, but honeybees keep a HUGE diversity of "what if" genetic codes stored in them.