[Last Visible Dog]

Species that do not reproduce but CAN are lions and tigers. Without our assistance, they'd never reproduce. That's why they are different species.

So you are saying if two groups of animals CAN reproduce but don't are considered different species - OK - what are groups that CAN'T reproduce called?

Like I said earlier - can you provide any supporting evidence for your claims?

[Stultis]

So you are saying if two groups of animals CAN reproduce but don't are considered different species - OK - what are groups that CAN'T reproduce called?

They're also separate species. I don't get your point. Whether they can't, or simply don't, or even if they do but hybrids are sterile, of if they do with sufficient rarity that population genotypes are unaffected, etc, whatever. In all these cases their populations are reproductively isolated.