Thanks Will, that's a really good point. I shall add it to the master copy of
the report.
I noticed John Haverson mention on a forum recently that his bees inHampshire
have that non-symptomatic version of the Deformed Wing Virus too, so given that
it was first noticed round Swindon it does seem to be showing up a lot in south
/ mid Oxfordshire, hurrah!
About genetic variation in bees, I came across an interesting point on this in
a BIBBA article which casts light on how inbred most commercial bees are.
BIBBA is a group trying to use conventional bee breeding techniques to make
better local bees (or better Amm, the original British black bee - there are
various sub-groups within BIBBA which I think has 1000 -2000 members across the
UK).
One thing breeders have to watch out for is inbreeding. In bees the big danger
is causing diploid drones, which are a mix of male/female like sterile drones
or non-working workers: too many in the mix and the colony collapses from too
many mouths / too few workers.
The percentage of diploid drones increases if you have too few variants of bee
sex alleles in the genetic mix. If you breed from one queen, after a couple of
generations all the subsequent queens and drones are so genetically similar the
bee colonies collapse. So commercial breeders control who breeds with whom very
carefully and try to maintain multiple different lines simultaneously.
If they do this well, said this article on breeding, they may have 12 different
sex alleles in the population which is good, but if it ever falls as low as 7
the diploid drone problem will overwhelm the colony with dud workers.
Then the article mentioned in passing that in the wild, in a well populated bee
area, there are 20-22 different alleles within mating distance of a hive.
Whoa. Back up a minute there. So what they're saying is:
If you buy commercially bred bees (Buckfasts, etc) they may have a "healthy"
spread of 12 sex alleles in their genetics. But if you simply allow your bees
to free-mate, they will likely have access to 20-22. I assume this applies to
all other aspects of their genetics too.
So IF varroa resistance is due, or partly due, to behavioural traits carried
genetically, it's no wonder feral colonies survived. They had access to a much
wider range of behavioural switches than the inbred commercial bees used by the
self proclaimed "experts" of the BBKA.
Right now conventional beekeepers continue to deny there are any varroa
resistant bees around - because they have bred out that ability from the
strains they use.
Paul
-------- Original Message --------
On 13 February 2018 7:20 AM, Will H whanrott@xxxxxxxxxxx wrote:
This academic paper is interesting on the subject of long term survival
of colonies which are infested with Varroa:
https://www.nature.com/articles/ismej2015186
The short version is that the lethal aspect of Varroa infection is the
Deformed Wing Virus which accompanies the Varroa. There are DWV
variants, some of which are non-lethal. Where these variants co-exist
they compete to exclude each other. If a colony has variant B then it
may survive in the longer term. The paper is rather technical in places.
Two of my colonies have been tested. Both have variant B which I think
is prevalent locally. My reading of the paper is that it isn't
guaranteed that Variant B will automatically triumph but it has around here.
If Super-exclusion in DWV is the cause for long term survival then the
bees genetic adaptations are less important. If I've understood, it's
more important what their Varroa are transmitting. This has consequences
for the argument about local bees. There are good reasons to choose
locally adapted bees, but Varroa tolerance probably isn't one of them --
their strain of DWV probably is.
In practice I don't think that this changes anything for our group. Take
swarms from survivor colonies. Choose local swarms for all your
preferred reasons but don't infer that they're magic bees just because
they've survived.
This paper also looks interesting (although I've only read the abstract):
https://www.researchgate.net/publication/316024861_Oldest_Varroa_tolerant_honey_bee_population_provides_insight_into_the_origins_of_the_global_decline_of_honey_bees
Will
