[muawiyah]

My sources says YES, in recently divergent species, this works (they believe) exceptionally well to keep species separated. Read more closely.

[allmendream]

They would help keep the species separated, just as the fact that mules are (usually) infertile helps to keep donkey and horse species separate.

But it would NOT in ANY way shape or form - prevent the production of a hybrid ‘mule’ between the species. A sterile mule is a dead end that cannot ‘blend’ the two species (like coyote and wolf hybrids can and do blend the two species).

In a male - meiosis doesn't even take place until adulthood - so how could a barrier to successful meiosis in a hybrid prevent the production of a viable hybrid? Answer - it could not.