> If I have to bet I say that mites adapt faster to bees than bees to mites.> Why? There is a lot more genetic variability with bees with multiple > external mating by queens compared with brother:sister mating among mites. On the > other hand there is a fresh generation of mites every month or thereabouts > but a fresh generation of bees only every couple of years or so.
...because of the multiple mating in bees it will take longer (smaller chance) to fix a trait like "tolerance". Fixing traits into the mite population will be easier (bigger chance) due to the sister-mating system that has less mixing of genes. And indeed the quick generation time.
But I do not know how big the difference is between mites and how much genetic variation they have. In an "isolated world" (limited transmission of mites between hives) I kind of expect genetic variation for Varroa between locations (space/time) because they have a sister-mating system responding to different selection pressure with little mixing of genes.   
 
I think we spend too little time looking at mites (genetic diversity and virulence). 
 
I am also not sure about genetic variation in bees with all the inbreeding we have done. Some people sell hundred/thousands of queens that are more or less related and go to islands to narrow down the chance of unknown mating.
 
ATB
L 
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