Hi all
We have been discussing the fact that varroa mites are an inbred, virtually clonal population. Be that as it may, there is variation by virtue of mutation. So, there are separate lineages, and these have host specific adaptations. 

Solignac et al. [13] estimated the divergence time between the Korean and the Japanese Varroa
type between 5 000 and 15000 years ago. Assuming a constant mutation rate and
population size, we can estimate the divergence time among the various haplotypes

Our results show that the arm race between Varroa and its hosts has led to the evolution of
very specialized mites. Although the underlying mechanisms of this coevolution are not well
understood, previous work suggests that the mite is able to mimicry the cuticular hydrocarbons
of its host [27–28] to avoid the hygienic behaviour of the honeybees [29].

Citation: 
Beaurepaire AL, Truong TA, Fajardo AC, Dinh TQ, Cervancia C, Moritz RFA (2015) 
Host Specificity in the Honeybee Parasitic Mite, Varroa spp. in Apis mellifera and Apis cerana. 
PLoS ONE 10(8): e0135103. doi:10.1371/journal.pone.0135103
OPEN ACCESS

* * *

Be that as it may, I think the harm from varroa vectored viruses is clearly the problem. These recombine and mutate at a very rapid pace, acquiring competitive genes almost “at will.”

Pete

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