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Thread: Yet another puzzle

  1. #1
    Administrator gavin's Avatar
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    Default Yet another puzzle

    Ah, the tribulations of sticking your head up above the parapet.

    You need a thick skin, but it does get tiresome.

    Last year I made a proposal for a bee research project, and asked Eric McArthur as organiser of the CABA apiary at the time if he would cooperate in this. He agreed and so I wrote this into the proposal:

    'As part of a survey of the degree of genetic mixing of races, the opportunity will be taken to assess diversity at the csd locus, the major driver of reduced fitness in inbred stocks of honeybee. An assessment will be made of progress being made by a beekeepers group in the west of Scotland to counter inbreeding by the exchange of stocks from isolated locations into and out from a shared apiary site.'

    It was a small part of a larger proposal, but it shows how seriously I regard the need for diversity at the csd locus (=gene). Didn't get the money of course.

    And yet tonight he wrote this in an email to me:

    >From: apisscot <eric@XXX.XXX.com>
    >To: Gavin Ramsay <diseases@scottishbXXkeepers.org.uk>
    >Sent: Tuesday, 7 September, 2010 16:17:31
    >Subject: Radio 2 Tuesday 9th Sept 2010
    >
    >
    > Hi Gavin
    >
    > I saw this and thought of you! Stick with it! One day you
    > might just learn something from your more informed and
    > open-minded peers! Only a fool would deny the outcome of a
    > closed population - as YOU did! No apology required!
    > "Facts are chiels that winnae ding"!
    >
    > Best regards
    >
    > Eric


    He was referring to this news item:

    http://www.bbc.co.uk/news/science-en...ry_continues_1

    and attached to the email was a copy of an article he published first in the Beekeepers Quarterly then the Scottish Beekeeper. I'll let you all see the article which he has kindly scanned for you all (Inbreeding limit&#9.jpg).

    So here is the puzzle. Eric's BKQ/SB piece where he lays out his theory for why bees are doomed due to inbreeding (where he insults 'dogmatists', meaning me I think) contains some utter nonsense about the loss of alleles at a crucial locus. Surely it is just commonsense, or do you need a scientific background to see just how flawed his arguments are?

    Some background information first. The 'csd' locus is the 'complementary sex determination' gene. If you have two different versions ('alleles') then you are female (if you are a bee). Just one, and you are a (haploid) male from an unfertilised egg. If you have two the same then you should have been a worker but the lack of difference between the two copies of the gene mean that you are functionally male. These 'diploid drones' in worker cells are usually removed at an early stage and are a major drain on the colony.

    There is said to be around 19 different alleles of this gene in honeybee populations. So let's go with Eric's 16 different csd alleles, it isn't far from the truth. Perhaps you could also assume that each virgin mates with 15 random drones. Now consider an isolated apiary of 10 unrelated colonies. See if Eric's scheme shows any signs of being linked to reality, and if not where has he gone wrong?

    Gavin

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    Senior Member Jon's Avatar
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    Dorian Pritchard did a good presentation on 'Inbreeding, its consequences and management' at the Bibba conference last weekend.
    He mentioned 20 alleles but that's not too far from either 19 or 16. he may even have said 'about 20' but I wasn't taking notes.
    One of the things he pointed out is that there is a very fine line between success and failure at a certain point and the tipping point is when a population drops to around 6 of the sex determination alleles.
    He put up various graphs and the difference between a 75% chance of winter survival and 25% chance of survival was a relatively small difference in the number of diploid drones produced. ( when the number of alleles in the population was already low)
    Diploid drones are removed by workers within 12 to 24 hours of the egg hatching.
    I think the chance of dropping to 6 alleles has got to be remote unless you are talking about a small number of colonies in an island situation.
    Your name came up at one point - I think in the context of the last SICOMM conference.

    PS.
    I just read the scanned article and I agree that Eric has got the wrong end of the stick re. how population genetics works!
    Last edited by Jon; 07-09-2010 at 11:07 PM.

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    Administrator gavin's Avatar
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    Dorian knows his stuff.

    Eric's contention is that in 10 colonies you start with 160 alleles (?!) and that each year if you have 50% losses then you lose half them every winter. 160 becomes 80 alleles in year 1 and so by year 5 your 5/10 fluctuating apiary is down to 5 alleles.

    Each virgin queen in this isolated apiary will mate with a random sample of all drones in the apiary.

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    Senior Member Jon's Avatar
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    I think it is just a misconception about how genes are distributed within a population.
    I discussed this with Doris as she was worried about the limited number of colonies on Orkney.
    I reckoned that bringing in fresh genetics could do more harm than good unless you had proof that one or more alleles was absent from the island population and that the new blood would add that gene.
    It's not the kind of thing you would do at an amateur level.

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    Administrator gavin's Avatar
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    The sort of pseudo-scientific nonsense that gets into some beekeeping magazines confuses people on what the real threats are and, as you say, can lead to people doing more harm than good.

    In *one* colony in a well-mixed apiary you could in theory have all 16 alleles (possibly even twenty) as the queen carries two alleles in each of her own cells and maybe another 15 in her spermatheca. In reality not all drones that mated with the queen will carry a different csd allele, but you get the idea.

    Halving the number of colonies from 10 to 5 may mean that you lose no alleles at all. Losing one might be a possibility. As Dorian said, losing a few wouldn't be critical, and when numbers fall a little more then there is strong selection which favours the survival and propagation of the more diverse colonies.

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    Senior Member Jon's Avatar
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    I think Doris said there are something like 80 colonies on Orkney so probably no immediate cause for concern although the situation should obviously be monitored for any increase in Diploid drones.
    Dorian P also stated that the natural gap rate in 100 cells is 6 so you have to subtract 6 from your sample of 100 cells when estimating the % of diploid drones.

    The problem with genetics in general and bee genetics in particular is that it does confuse most people. (myself included)

    Roger P stated at the start of his talk that as far as he was concerned genetics was a concept dreamed up on April 1st.
    Last edited by Jon; 07-09-2010 at 11:49 PM.

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    Administrator gavin's Avatar
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    I understand that there is a small apiary in a very isolated part of mainland Scotland which today shows exactly the same rather unusual tight morphometry plots as it did when surveyed in 1993-94. More will be revealed at the bee breeding day in Fife in November.

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    Administrator gavin's Avatar
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    Quote Originally Posted by Jon View Post
    One of the things he pointed out is that there is a very fine line between success and failure at a certain point and the tipping point is when a population drops to around 6 of the sex determination alleles.
    He put up various graphs and the difference between a 75% chance of winter survival and 25% chance of survival was a relatively small difference in the number of diploid drones produced.
    If you have three colonies fully isolated from all other apiaries then it will be hard to maintain 6 alleles in the long term. Easier with 4 colonies, not so hard at all with 5. The bottleneck is the queen. Each queen can only make drones of two types as the drones arise only from the genes carried in her own cells. The workers and queens each queen makes can be more diverse as they are fertilised with stored sperm, but over time this strong filtering when queens make drones will reduce the diversity in such small isolated populations. Of course few apiaries are really isolated. I would doubt, for example, that Mull is fully isolated from the mainland.

    To misunderstand all of this, write an article castigating 'experts', robustly put forward a completely wrong view that is going to confuse everyone, then arrogantly declare 'I rest my case!' is fairly typical of this writer. We really need magazine editors that actually sift such pieces for quality and accuracy before they give them space.

  9. #9

    Default Inbreeding in Honey bee colonies in a close population

    Hi Gavin and Jon

    Reassuring to see such a flurry of activity on such a tight time scale - the oil supply for the midnight oil lamps must have taken quite a 'tanking', (excuse the pun!) over that 8 hour time scale. I hope that the inbreedng issue will encourage many more hits than just the three of us. At the time I wrote the initial piece on the inbreeding problem facing Scotland's bees I had hoped to involve a geneticist in Strathclyde Uni but unfortunately this involvement it appears was discouraged by a more senior member of staff.
    At the time Roger Paterson was having trouble with his queen bee failures I wrote suggesting that his problem was most likely inbreeding. This postulation was supported by an eminent beekeeper in Ontario, Canada in an e-mail at that time to Nigel Hurst, editor of the Scottish Beekeeper
    Inbreeding in the honey bee has long been ignored by most beekeepers. "The problem doesn't exist"! Hmmmm. That was a numbere of years ago when I first mooted the dangers of inbreeding at a Glasgow and District meeting some years ago in the company of Ian Craig and a number of other experienced beekeepers - to a man they had never even considered the phenomenon.
    Inbreeding is now coming high profile as honey bee colony and experienced beekeeper numbers diminish. The key word is "experienced"!
    The inbreeding situation on Islay, in which I became involved in the early 70s, when I was the only beekeeper in Scotland actively marketing queens and nucleii gave me a deep insight into the problems of inbreeding, which actually ran parallel to the Paterson queen situation. Paterson implies that genetics was a device dreamed up by some April fool - tell that to Sir Alec Jeffries or Crick and Watson.

    Now to the nub of the matter - in a closed population of 10 colonies entering their first winter, losing 50% of its number each winter but re-establishing the complement to 10 colonies each subsequent summer with the gene pool remaining; Since genetics is such a closed book - simplify the situation by substituting a letter of the alphabet for each individual colony- vis:
    A,BC,D,E,F,G,H,I,J. So in the spring there are only 5 of the original colonies left: eg - A,C,E,G,H.- Go on do the elimination randomly and see how many generations it takes to have a classic inbreeding situation.

    Eric McArthur

  10. #10
    Senior Member Jon's Avatar
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    Quote Originally Posted by Eric McArthur View Post
    Hi Gavin and Jon

    Now to the nub of the matter - in a closed population of 10 colonies entering their first winter, losing 50% of its number each winter but re-establishing the complement to 10 colonies each subsequent summer with the gene pool remaining; Since genetics is such a closed book - simplify the situation by substituting a letter of the alphabet for each individual colony- vis:
    A,BC,D,E,F,G,H,I,J. So in the spring there are only 5 of the original colonies left: eg - A,C,E,G,H.- Go on do the elimination randomly and see how many generations it takes to have a classic inbreeding situation.

    Eric McArthur
    Hi Eric.
    I think you are misunderstanding how this works.
    You can start with ten colonies, lose 5, increase to ten the following year and still maintain every one of the CSD alleles.
    Unless you are in a completely isolated situation, there will be incoming genetic material from neighbouring colonies via their drones.
    Even in an isolated situation, bees can maintain genetic diversity as the queen mates with multiple drones.

    Gavin explained it with the following two quotes:

    Each virgin queen in this isolated apiary will mate with a random sample of all drones in the apiary.
    In *one* colony in a well-mixed apiary you could in theory have all 16 alleles (possibly even twenty) as the queen carries two alleles in each of her own cells and maybe another 15 in her spermatheca.
    This means that each and every queen in the apiary is likely to carry most of the csd alleles so even if half the colonies are lost each winter, there is not necessarily any loss of csd alleles.
    The misconception is that losing half the colonies equates to losing half the genetic material and this is not the case.
    If you read some of the papers by Beye et al you will see how this works.
    Last edited by Jon; 08-09-2010 at 07:57 PM.

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