> Everything in honey bee biology seems opposed to selective breeding.

I bring up this fact time and again.  Honey bee reproductive biology allows
not only for rapid evolutionary adaptation, but also for recovery of a
breeding population's genetic diversity following devastating events such
as wildfire, extreme weather, or epidemics (since, due to polyandry, every
mated queen carries a cross section of the genetics of the previous
season's breeding population).  Honey bees may be the most difficult
managed species to selectively breed.

 >Selection means narrowing the genetic diversity;

In general yes, but the statement calls for elaboration.  Selection can
also mean mere rearrangement of the coding and regulatory alleles, or a
shift in their prevalence, rather than a "narrowing" of diversity.

Loss of deleterious alleles (such as those that cause disease) from a
breeding population would indeed narrow the population's genetic diversity
-- but such loss of those "bad actors" may be of benefit to that
population.

Or selection may instead simply shift the prevalence of certain
arrangements of the existing regulatory cascades by favoring certain
"algorithms."  In this case, a population could experience strong selective
pressure, without any loss of genetic "diversity."  Genetic "change" does
not necessarily imply any "loss," but might instead reflect only a
rearrangement of alleles or regulatory pathways.

Or selection could simply shift the overall prevalence of existing coding
alleles (more aces in the deck), such as increasing the prevalence of a
rare allele that codes for a protein that allows an olfactory receptor to
detect varroa mating pheromone).  No alleles needed to be "lost" -- all
that selection might do would be to increase the prevalence of a critical
allele in the breeding population overall.  Keep in mind that it may take
only a single patriline of workers carrying that single allele to confer
varroa resistance to the colony as a whole.

Luckily for us breeders, there are two simple visual  indicators of genetic
diversity that we can keep an eye on -- loss of sex alleles (indicated by
spotty brood patterns) and color/marking diversity.  Neither are likely
linked to varroa resistance, so can likely be used as a proxy of
conservation of genetic diversity in one's breeding population.

Another help can be the surrounding feral population, consisting of both
"wild type" resident bloodlines and escaped swarms from the managed
population.  Those colonies that don't exhibit resistance to varroa won't
be sending out drones the next year.  So they constitute a concurrent Bond
selection process going on in the neighborhood surrounding one's mating
yards.  They also act as a reservoir for locally-adapted genetic diversity.

Randy Oliver
Grass Valley, CA
530 277 4450
ScientificBeekeeping.com


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