Hi Bill

> So Tom's bees are not the hoped for
> resistant bee that some might think.
> In time they might be, but not now.

I've always had a hard time seeing it this way.  Yes, hosts and pathogens co-evolve.  Yes, it is feasible that Varroa might become less virulent in time.  But ....

Varroa has very little genetic variation for selection to act upon.  It came through a huge bottleneck when it jumped to Apis mellifera and left behind most of its accummulated diversity.  Huge selection pressure has revealed the very rare variants (probably new mutations) that can resist pyrethroids, but where has the variation for virulence come from?

Eventually, host and parasite may settle down to co-exist.  It is better for both.  The host clearly benefits from being able to tolerate the parasite.  But where is the selection pressure for the parasite to be kinder to its host?  Virulent mites multiply faster than non-virulent ones, and take over any mixed populations.  Virulent mites cause their colonies to collapse and so virulent mites jump colonies more often.  Virulent mites survive any emerging resistance in the bee better then avirulent ones.  In an environment with mites jumping between colonies, I just can't see how avirulent mites could become dominant.

Tom Seeley's bees might be tolerant of Varroa for other reasons, and perhaps these reasons are not stable - or effective enough - when transplanted from the forest.

Keep an open mind, that's all I'm saying.

best wishes

Gavin

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