From: Bill Lucy 

In article , email{at}from_Gary_Britt.org says...
> Are you trying to state that a male and female donkey can mate and produce a
> baby donkey?  If they can't then it shows that a horse and a mule are
> different species.

According to *your* definition, the mating of a jack donkey and a mare (two
different species) cannot produce a viable^h^h^h^h^h^hfertile offspring.
Although rare, the result is a mule (female always) called a
"hinnie". And that animal is fertile. At the very least, that
makes your original definition of a single species unworkable.

I probably should not have included the example though, because the rarity
clouds the point. Two different species can and do interbreed, creating
offspring which are viable and fertile. As Bob Comer implied (regarding
poecilliidae), the differentiation from the one parent and the other may be
slight, but it's significant enough for taxonomists, and I assign a lot
more credibility to them than to what you or I can say regarding the
subject.

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