Generally, different races within a species can reproduce when crossed and
have viable offspring, that themselves are fertile. This is not true between
species, which may be able to reproduce, if close enough in characterics,
but generally are not able to be crossed. Hence, cats and dogs cannot be
crossed into a hybrid (leaving out GM), and horses and donkeys when crossed
produce sterile offspring - mules.

Within a race, characteristics are generally homogenous (not all, but a
significant number), breeding true from one generation to another. when
races are crossed, you have variability in the characteristics in which they
differ - some are dominant and show in all offspring, others are not. In
later generations, you end up with more variations - possibly including some
that are now "pure" in the characteristics of the original parent races. The
more the two races differed, the greater the number of variations you end up
with.

So, with Buckfast bees and enough generations of interbreeding, you could
end up with individuals that were indistinguishable from each of the
original species used to create them. If that includes the african bees, you
could end up with a hive of very nasty bees. Right next door could be a very
gentle hive, with most of the characteristics of the Carniolan.  Over many
more generations, you could end up with a new race of bees (provided you had
sufficient isolation), with the characteristics of the best survivors. All
of this assuming you as the beekeeper don't help by selecting for those
characteristics you desire - such as destroying those aggressive hives.

-----Original Message-----
From: Robert Brenchley

 it's obvious that
horses and donkeys, for instance, are separate species, but marsh orchids
are
not so obvious.