Posted 08 October 08
Queen Quality – Genetic Deficit – What does the Future Hold?
By Eric McArthur
(By kind permission of BKQ Sept 08. Vol.93 p.31)
As a beginner beekeeper in the early ‘70s I attended a conference at Auchincruive, this in the hey day of the Agriculture College resident Bee Adviser. Just prior to the conference I had been reading about the German Körung selective breeding system – whereby beekeepers from all over Germany working with Carniolans sent their virgin queens to be mated at the isolated mating stations on the islands off shore from East Fresia. These mating stations have massive populations of specially selected drones which guarantee good quality ‘male line’ pure bred bees. At the Auchincruive event, a workshop on queen rearing had been organised among others – I opted for the queen rearing. The demonstrator was a well respected Adviser and I looked forward to a ground breaking session. Sadly, I was extremely disappointed. The lecturer informed his assembled audience that it was not necessary to have any more than one selected drone colony in the mating apiary since most beekeepers were only interested in producing a few new queens. I questioned his statement, quoting the work done by the German breeders. He stated that had never found any problems achieving high mating success rates and good quality queens with the method submitted, which was of course quite true. Cast the mind back to the ‘70s – well ‘pre Varroa’. The mating successes in the ‘70s, were related to the high incidence of feral colonies and other managed bee colonies in the particular beekeeper area.
This single drone colony doctrine was reinforced by another procedure, which due to it having been advocated over a number of decades, perhaps even centuries was knee jerk beekeeper lore – breed from your best colony or colonies! However today many of Scotland’s beekeepers having to a greater or lesser degree moved on from the ‘single drone’ colony, still practice the ‘breeding from the best’ procedure. The ‘breeding from the best colony’ method succeeded for the same reasons as the ‘single drone’ colony method - sufficient supplementary mating potential due to high bee/beekeeper and feral colony density.
Thanks to the predations of the Varroa mite and associated viruses it is no longer sensible to breed from the best stock(s) in an apiary, especially an outfit with less than 50/60 unrelated colonies. Why? - for exactly the reverse reason that the method was successful in the past. Most beekeepers then did not even consider the critical contribution of the feral colonies to maintaining a ‘sweet’ gene pool, despite the potential massive reduction in their apiary gene pool – viz 10 colonies year one - one ‘best queen’. Future generation of 10 colonies reduced over time to one gene pool on the female side – without the feral colonies and other nearby apiaries the genetic degradation would have been enormous.
There are some areas of the world where the honey bee populations are close to nil. Scotland is at particular risk due to its relatively small number of colonies. The situation in particular areas of America would appear to be heading in this direction – bee colonies in such areas have virtually no chance of survival in a breeding from the best scenario – titlehough the ‘best’ performance will be a downward spiral – blamed initially on poor weather – until the proverbial penny drops and the beekeeper realises that his colonies have become inferior due to inbreeding – perhaps too late.
I have had discussions, even heated argument with educated beekeepers, even those with academic qualifications in the biological sciences regarding the dangers which I perceive threatening the world honey bee gene pool.
I postulate that the high colony losses incurred in the recent past and currently, will ultimately produce a critical mass situation from which a population recovery could be impossible. My critics respond with – “Massive honey bee colony losses have occurred throughout history and the bee has bounced back – naturally”! What short memories even in the light of recent history the dogmatists tend to have! The Americans have a saying “Remember the Alamo”! The Scots and the English should be looking back and remembering “Isle of Wight”, when the UK’s failing honey bee population had to be bolstered by massive imports from world wide. With regard to recent history and Varroa the perils of high level honey bee imports currently is fraught and the cure could be worse than the ailment – vis SHB, T.clarea and perhaps worse!!
Returning to the dogmatists in the previous paragraph – the older members of the
beekeeping fraternity will remember the UK summer of 1985 during which, because
it was so bad a massive 75% colony loss was incurred. The dogmatists have it
here – the high colony losses were soon made good and beekeeping continued
apace. However there are three factors relative to ‘85, which the dogmatists
fail to consider:
1. The major colony losses incurred were among the managed honey bee population, the ferals not having been robbed blind by a benevolent/ malevolent beemaster had adequate stores with which to weather that poor year.
2. We as beekeepers were still enjoying the halcyon days pre Varroa and the feral colonies were still intact to supply the necessary unrelated drones from which to regenerate.
3. Currently as the honey bee populations gradually reduce to a ‘Singularity The ferals which were there unheralded in the background during the crisis in ’85 are no longer with us in the same density.
My maths/arithmetic are not of the best’, but consider the case of an isolated closed honey bee population in any particular area.
The honey bee is reputed to carry some 16 sex alleles, therefore in a totally closed population in a ‘Doomsday Scenario’ of say 10 unrelated colonies there could, best case scenario, be initially a total of 160 sex alleles. Now consider the situation where a 50% colony loss is incurred year on year and the colony numbers are reinstated every summer to 10 from the survivors.
|Consider 1: 10 colonies -160 unrelated sex alleles|
|Year 1....10 x 16 unrelated gene pools = 160 unrelated alleles|
|50% losses.....5 x 16 gene pools = 80 unrelated alleles|
|Year 2................10 x 16 gene pools = 80 unrelated alleles|
|50% losses.....5 x 16 gene pools = 40 unrelated alleles|
|Year 3................10 x 16 gene pools = 40 unrelated alleles|
|50% losses.....5 x 16 gene pools = 20 unrelated alleles|
|Year 4 ...............10 x 16 gene pools = 20 unrelated alleles|
|50% losses.....5 x 16 gene pools = 10 unrelated alleles|
|Year 5 ...............10 x 16 gene pools = 10 unrelated alleles|
|50% losses.. ..5 x 16 gene pools = 5 unrelated alleles|
|Year 6...............10 x 16 gene pools = 5 unrelated alleles|
|50% losses.....5 x 16 gene pools = 2 unrelated alleles|
|Year 7 ...............10 x16 gene pools = 2 unrelated alleles|
Thus in 6 generations critical mass is reached!
Thus as a honey bee population reaches critical mass, even in a ’best case scenario’ starting with a totally unrelated gene pool (highly unlikely!). Within 6 generations the diminution of genetic diversity would seem to be irreversible.
According to “Dadant’s “the Hive and the Honey Bee” page 258 - ‘Difficulties’
“Inbred lines are difficult to maintain and are easily lost. This is primarily due to a consequence of their ending up with only 2 sex alleles within lines. This in combination with other effects of inbreeding depression results in a high likelihood of colony failure and loss of lines”.
I rest my case!