That's a bit unnecessary, John. If IOW disease swept though, destroying most of the Amm before it, and the Aml stock was resistant, then what would happen would be that Amm would be lost and Aml would take over. You'd end up with Aml and Aml-leaning hybrids. That didn't happen - presumably what happened is that there was resistance in the Amm stocks and that they repopulated areas that lost stocks when IOW struck.
Why so Gavin? If the resistance was there in the A.m.m. stock why did it take the best part of 60 years for it to stabilise? Acarine was still a big issue as recently as the 1960s in black stock. Yes the bees are more or less unchanged blacks nowadays, but they went through a long period of turmoil until a largely strain stable bee emerged which is most likely 95% Amm, but with crucial inclusions of benefit from the incoming genetics, and you could do morphology from now till the end of time and not spot it.
It is also a moot point if a bee which can survive is the same bee as the one that is desireable to keep. I can see where both types would have their followers (perhaps not the best word given certain , from our own experience unjust, labels attached to hybrids).
My contention, and it IS merely a theory, is that there was an overlap period where the new stock was in the area and the last of the old bees had not yet died. Some hybridisation took place. Over the very long time scale the old bee genetics gave the resistant bees incorporating them an environmentally influenced marginal advantage, and they then went on to mate with other colonies with some of the old genes in them and so on over many generations. To take so long for it to arrive at todays situation implies that the genes for the old blacks must have become pretty dilute in large areas, less so in others.
Why not back to Aml types? Well environmental factors heavily favour Amm, disease factors favour a TINY factor in Aml and discriminate strongly against a TINY factor in Amm. You could possibly, by natural routes, say we now have a GM Amm as our feral/local bee. Took many years to sort itself out though.
Besides, IOW disease would have encountered mixed stocks in England before it reached Scotland, so if your hypothesis is correct then hybridised Amm types would have thrived in England too.
I believe in certain parts they do, and like in Scotland it is primarily at the extremities or in harsh environments, where those very environmental factors favour the black bee and cause the same biases to drift back towards native to take place. There are also large tracts of England where the environment and climate today do not create this bias and carnica genetics in particular are at least a match for them, plus the Buckfast complex hybrid also was bred for English conditions, so in at least the southeastern half of England the tendency to revert to native is less prevalent, even absent.
It is abundantly clear that man has been bringing in exotic bee races for a long time. Yes, it is perfectly true that no-one can guarantee that any Amm around today is exactly the same as the Amm around before any deliberate imports, but they must be close.
I do not see how we are arguing on this. Its is pretty well what I think, albeit coming at it from the other end.
I still return to the point that if stocks tend to return to something like Amm over time then that shows the best direction to go.
On that one we differ. If we did it would be wild oats and primitive livestock in farming today. Improved varieties would not have a sustained place. Aspiring to what nature will drag you back to in an unmanaged situation leads that way. As soon as you indulge in lots of selection you are moving away from the local model to one that will drift back to it if left to its own devices. I know that is not exactly what you are saying and that you believe in selection from that stock, but that rather contradicts the statement that what the bees naturally revert to shows you the way to go.
LOL!! You are starting to sound like Dee Lusby now Murray. Didn't she use that turn of phrase? You'll be forcing your bees into unnaturally small comb next ....