Murray McGregor provide some very insightful comments in his response of
15 January to my posting about feral colonies and natural selection for
resistance to varroa mite infestation. I have no quarrel with his comments
but wish to provide just a little more input in response to his excellent
comments:
**********
Murray wrote:
>I think I would need more substantial evidence of resistance than this
>before comitting to the strategy of securing matings only with similar
>feral colonies. (As no doubt does Adrian, with his scientific
>background)
Murray is correct on that point. What I suggested was only a starting
point for further consideration about the matter.
Murray also wrote:
>During its lifespan it may issue quite a number of further swarms and
>castes itself, each again leaving much of the mite load behind at the by
>now parent colony. This parent colony then collapses, and much (except
>those moved on by absconding bees) of the mite load dies with it.
>
>This will mean that strains disposed towards swarming will be very
>strongly selected towards, as the non-swarming colonies collapse having
>issued relatively few progeny, to be replaced by the numerous swarms
>from those colonies of a swarmy nature.
>
>It will only take a very few seasons for this strain to become dominant
>over the less vigourously swarming types generally produced from managed
>colonies.
*************
I believe that Murray is correct on that point, a point made by me on
this list on 31 October 1997, in response to a posting made by Paul
Cronshaw --- a quite special beekeeper in Santa Barbara. That earlier
posted comment follows:
**********
Paul Cronshaw wrote:
>I am still getting swarm calls at this time of year in Santa Barbara. The
>sizes of swarms range from fist size to soccer ball size. All have queens.
>
>I am wondering if these swarms are the result of mites. The bees are
>breaking the mite breeding cycle by swarming at this late in the season. I
>understand this is a trait of the AHB.
>Perhaps we are seeing survival of the fittest occurring in the local bee
>population?
I think Paul is correct and have already suggested that possibility
elsewhere (the latest with Dr. Yaacov Lensky from Israel, when he
interacted with Robbin Thorp and me last week out on Santa Cruz Island).
That is, we can expect that natural selection will first be more evident at
the colony level (as in frequent swarming) than at the individual behavior
level (as in a few of the workers biting mites). Some of the colonies that
swarm frequently will persist long enough to send out other swarms, etc.
By contrast, workers in a colony are a motley crew --- collectively
derived from a dozen or more drones. If, for example, an insufficient
number of workers fight mites, colony death will occur --- along with the
mite fighting workers, who don't reproduce anyway.
*******
*********
Further clarification (hopefully):
Virgin queens mate with drones from a good many different hives. Simple
rules of biology thus prevail. If the vast majority of those nearby hives
have been kept alive with Apistan strips, those queens on mating flights
will likely acquire sperm mostly from drones that carry virtually no
resistance to varroa mites.
By contrast, in an area without managed colonies (and where no one uses
Apistan strips), queens will mate almost entirely with drones from colonies
that somehow have resisted the depredation of varroa mites.
In other words, we must think in terms of a population of colonies, not
in terms of individual colony tolerance of mites.
Adrian
Adrian M. Wenner (805) 963-8508 (home phone)
967 Garcia Road (805) 893-8062 (UCSB FAX)
Santa Barbara, CA 93106
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**********
*
* "The flaws of a theory never lead to is rejection....Scientists
tolerate
* theories that can easily be demonstrated to be inadequate."
*
* Carl Lindegren, 1966
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**********
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