>But do we have evidence that this is genetically based rather than
environmental? In other words, if I put them in my hives, will they be
resistant here? My experience this summer with resistant stock from Texas
was that they had half as many mites as non-resistant stock. But still went
over the threshold, and had to be treated.

Pete, such has been my experience in the Calif foothills.  I've tested
putatively resistant stock from all over, and most, but not all, fail the
test.

The Russians would be the exception, with a percentage of them handling
mites and viruses pretty well, although I applied minimal treatments in
fall to help them.

And the occasional colony that completely manages mites, despite being in
the same environment, and surrounded by mite-infested colonies, suggests
that there is a genetic component.

The recent large-scale trials in Europe by the Coloss group support the
hypothesis that locally-adapted stock handle parasite pressure better than
imported stock.  This is no surprise, biologically speaking.

With my own stock, few would make it through the winter without treatment,
despite years of lower mite levels being one of my selection criteria.
However, when recreational beekeepers keep colonies of my stock in areas
without heavy pressure from nearby hives, a number report that those
colonies survive for 3-5 years without any treatments.  This observation
supports the influence of environment, as far as pressure of mite
immigration.

As far as your question as to heritability, I think that the empirical
evidence of the success of the Primorksy European stocks, the French
survivor lines, the Africanized bees, the long-surviving matrilines of U.S.
feral stocks documented by mitotype, not to mention Apis cerana, all
support the hypothesis that varroa/virus resistance is indeed heritable.

Re your interpretation of Oldroyd 1997, could you please cite the
reference.  In a paper by him in 1998 (Population Genetics of Commercial
and Feral Honey Bees in Western Australia), he concludes that:

"The representation of both subspecies in the mitotypes of the feral
population indicates gene fow from the commercial A. m. ligustica colonies
via swarming. This was not necessarily a recent event and does not imply
that the feral population is currently
being supplemented by swarms from commercial colonies."

As any of our Aussie members can attest, the feral population of Aussie
bees maintains itself under selective pressure by Nature, rather than by
that of mankind.

I'm currently very interested to see how the feral population on the Big
Island of Hawaii adapts to their three recently introduced parasites,
varroa, SHB, and N ceranae.  Some reports are that swarming is already
returning to previous levels.

Pete, as do you, I approach anyone who is claiming to have mite resistant
stock with great skepticism.  And then I do alcohol washes, ask about
marked queens, tracking of survivability, winter loss rate, etc.  The
evidence to date is that Mom Nature is ahead of many of our commercial
breeders as far as selection for varroa resistance is concerned.

-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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