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Instrumental Insemination and Allele Poverty |
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One of the problems of II using a limited number of colonies, often with related stock, is that the semen from different drones may contain identical genes.
The Gene pool itself may be quite large in as much as it may contain copies of many individual genes, but lack of diversity may limit the range of genes involved in a single insemination.
If many of the gene copies originated with similar ancestral genes... This can happen if a 'bottleneck' occurs. Whereby a population shrinks, due to severe selection pressures, to a few survivor individuals and all subsequent stocks are derived from them. We can consider such a population impoverished of genes.
America is often cited as a case of poor variety in bees since all bees were imported by European settlers in relatively recent times (say 500 years). The numbers of colonies was large, but many of them were derived from small breeding populations in UK and Europe. In the last century US beekeepers have been fixated on the Italian bee, which with it low mating frequency allows gene poverty to show up much more readily. However the gene pool in UK is derived from a large numbers of colonies that re invaded Britain after the last ice age and as they have been in place for millennia rather than centuries, mutation and a naturally high mating frequency has added yet more to their diversity.
Against this background we have breeding crosses being arranged that may only involve one particular drone by using instrumental insemination. I should stress that this is an extremely rare occurrence and does not provide an end in itself, but produces lines for further selection. There are other situations in breeding yards that can give rise to a queen being fertilised by several drones with identical genes. We also have the case where drones are raised in captivity for providing semen to be used in II. As only six or seven drones may be needed to provide the volume of semen required it is possible and or probable that a lack of diversity can occur.
It is this reason that leads me to think that we must put more effort into homogenised semen and the solvents and diluents that are needed to achieve this. In USA, Anita Collins has done a great deal of work on semen viability and semen longevity, her work is leading to an understanding of what enzymes are used in nature that allows semen to stay viable for the life of a queen (up to several years).
Originated... April 2000, Revised... 20 January 2003, Upgraded... 15 April 2006,
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