Hi again, Chris,
The paper is a bit deep for this forum, but absolutely fascinating!  Another
quote:

"This question is often raised, and the an-
swer, based upon the data we have accu-
mulated, is that it [epigenetic inheritance] may be ubiquitous. We
believe that epigenetic variants in every lo-
cus in the eukaryotic genome can be inher-
ited, but in what manner, for how long,
and under what conditions has yet to be
qualified. In other words, unlike the repli-
cation of DNA variations, which is largely
context insensitive, whether and for how
long a particular mark or cellular element
is transmitted between generations de-
pends on genomic, developmental, and ex-
ternal conditions."

And now for some stunners, related to resistance:
"The most impressive ex-
ample of somatic induction via small RNAs
may be found in the case discussed by Vas-
tenhouw et al. (2006), in which C. elegans
were fed bacteria with DNA sequences cod-
ing for dsRNA, and the RNAs migrated
from the somatic cells of the nematode to its
germ cells, thus affecting subsequent gener-
ations. Steele et al. (1998) suggested another
route of transmission that is initiated by
RNA: the transfer of RNA transcripts from
the immune cells of mammals to their germ-
line, followed by reversed transcription and
incorporation of the reverse transcribed
DNA into the germline genome."

What does it take to elicit resistance?

"We suggest that the inheri-
tance of some epigenetic memory traces
may lead to epigenetic recall—a facilitated
response in descendants that requires an
inducer."

And how about the variation in Varroa destructor, which apparently began
essentially as a clone of a single female?  In the case of inbred
populations:
"epigenetic variants are
often induced when environmental condi-
tions change, so several individuals in the
population may acquire similar modifica-
tions at the same time. This means that ad-
aptation through the inheritance of newly
induced epigenetic variants may be very
rapid"

The paper notes that hybrids can have substantial portions of their genome
silenced--a caveat for bee breeders!

Essentially, forget everything that you assumed about the genetics of bee
breeding and evolution:
"The epigenetic perspective challenges all these [genetic and evolutionary]
assumptions, and it seems that a new extended
theory, informed by developmental studies
and epigenetic inheritance, and incorporating
Darwinian, Lamarckian, and saltational frame-
works, is going to replace the Modern Synthe-
sis version of evolution"

A reading of this paper makes one realize how little we actually know about
the actual mechanisms of bee breeding and parasite resistance.  As Peter
Borst has suggested, perhaps we should take a good, hard look at our
assumptions as to the best way to breed bees.

Randy Oliver

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