Answer:
"Species" I believe would be the answer you are looking for.
Explanation:
It's kind of like Pokémon: Two Pokémon don't have to be the same type (such as a Pikachu and a Pikachu), but if you do want the two Pokémon to breed and produce offspring, they need to be apart of the same Egg Group/Species.
EX: Blastoise and Stunfisk can breed even though they are both very different Pokémon, they share the same Egg Group/Species, being the First Water Egg Group.
Hopefully that was a funny way of explaining it!
