> I am informed that Varroa destructor (unlike Varroa jacobsonii for which
it was at first mistaken) has never been found on Asian honeybees from
whence it was presumed to have transferred. Is that because we haven't
looked hard enough; that it has somehow become extinct where first it
developed; or that by a rapid evolutionary leap it transformed its shape
and (presumably somebody has compared) genome when it changed hosts?
Of interest:
"The transferring of mites across different species suggests that host
species also affects mite reproduction. When mites from *A. cerana* were
introduced to *A. mellifera* worker brood, only 10% of the mites
reproduced, while 80% reproduced when *A. mellifera* mites were transferred
to *A. cerana* worker brood. In our study, *Varroa destructor*, Korea
haplotype, from *A. mellifera* reproduced equally well (all > 90%
reproduced), regardless of whether it transferred to *A. mellifera* or to *A.
cerana*, in both drone and worker castes (Ting Zhou, Shuangxiu Huang and
Zachary Huang, unpublished data). In contrast, *V. destructor*, Vietnam
haplotype, from *A. cerana* only reproduced on *A. cerana* drones (83%
reproduced, N=62), and not on *A. cerana* workers (0% reproduced on
workers, N=60). These results suggest that the mites on the two honey bee
species are different: mites from *A. cerana* refrain from reproducing on
worker brood of the same species, and mites from *A. mellifera* reproduce
well on worker brood, regardless of the host species. It appears that only
the Korea haplotype of *V. destructor* had a genetic change that enabled it
to reproduce on either drone or worker brood in *A. mellifera*, therefore
allowing it to build up to levels damaging to the bees. In China, my
colleagues and I did not find damaging levels of *V. destructor* in *A.
cerana* colonies – in fact, in most locations, the mites could not be
found. When we found it, it was the Vietnam haplotype which does not
reproduce in the worker brood of *A. cerana*. It is not clear why the
Korea haplotype of *V. destructor* does not cause damage in *A. cerana*,
since they can reproduce in both worker and drone brood in transfer
experiments."
http://www.extension.org/pages/65450/varroa-mite-reproductive-biology#.UpYWTCfUfd6
--
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com
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