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 encountered.
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.
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 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.
Originated... April 2000,
Revised... 20 January 2003,
