Most species don't really need to be tested because their chromosomes are different enough to make it obvious their offspring would be infertile, right? Of cou

Most species don't really need to be tested because their chromosomes are different enough to make it obvious their offspring would be infertile, right? Of course if hybrids are infertile they would be considered different species. If hybrids are fertile, like your example of camels and llamas, then according to what reason would they be considered the same species? Did their evolution diverge and then reconverge? I guess it depends on your definition of "often".