Honey bee (Apis mellifera L.)
tolerance to Varroa in South America
Apidologie 30 (1999)

A general question is whether tolerance is
a trait of the honey bee or the expression of
lower virulence of the mite. The following
two facts support a mite-biased selection.

1) The shorter generation time of V. jacobsoni
versus honey bees should favour the
more rapid adaptation of V. jacobsoni to
selection pressure.

2) By use of genetic methods, three different
geographically isolated mite populations
could be distinguished in America
These groups may represent populations
with different virulence (or perhaps
tolerance levels of the host).

The different reproductive ability of two genetically
distinct V. jacobsoni populations from
Germany and Papua New Guinea, respectively,
has been demonstrated

In the case of the V. jacobsoni-honey
bee relationship, even a non-benign strategy
could be advantageous for the mite: if
environmental conditions favour the distribution
of mites into neighbouring colonies
from dying colonies through robbing or
drifting bees.

In general, it depends on environmental
conditions, parasite and host density
and gene flow within the parasite population
whether a virulent or a benign
strategy of the parasite is more adaptive.
For V. jacobsoni, this question remains
open.

A host-dependent tolerance to V. jacobsoni
is supported by comparative studies
with Africanized and European honey bees
in Brazil, which clearly reveal an influence
of honey bee race

Results from Uruguay demonstrate that
V. jacobsoni tolerance is not limited to
Africanized bees within a tropical climate.
Unfortunately, we have to face the fact
that V. jacobsoni tolerance is influenced by
multiple factors of the host, possibly by
genetically determined virulence of the parasite,
and additionally triggered by environmental
conditions. This combination of
factors could create different modes and levels
of tolerance depending on honey bee
race, origin of the mite and climatic conditions.

-- 
Peter L. Borst
Danby, NY  USA
42.35, -76.50
http://picasaweb.google.com/peterlborst

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