John asks,

> Can anyone help me understand this from a GENETIC viewpoint please?

Although not an expert, genetics was a favorite subject in college.

Breeding local bees only may limit the gene pool to the point where the
genes controlling unwanted traits are magnified due to queens mating with
grandsons.  I believe, eggs fertilized by sperm from a son are not viable.
A good analogy is the disease hemophilia that was rampant in the royal
families in Europe.  Since Royalty had to marry Royalty, close marriages in
the same family caused the gene for the disease, a recessive(needing two
genes), express itself.

By bringing in outside genes, the doubling up of recessive genes is less
likely.  Often, different strains or breeds carry recessive genes for
different undesirable traits, and therefore doubling of genes for a
particular trait is less likely.  Thus the phrase hybrid vigor.  Hybrids
tend to be stronger since unwanted traits are less likely to express
themselves.

There is a good book,  Equine Genetics and Selection Procedures, that can
explain this better than I.  Although it is, obviously about horses, the
theory is the same.

This raises a question from me, however.  I have been advised a couple of
times that Buckfast bees(hybrids) get nasty when they supercede their queen.
What strains were used to develop this strain of bees and why do they get
nasty?

Coleene