It's species or subspecies. Animal classification has always been a little bit fuzzy and has some legacy cruft laying around. Like wolves, coyotes, and dogs are distinct animals with different behaviors but are definitely capable of interbreeding.
https://en.wikipedia.org/wiki/Species
https://en.wikipedia.org/wiki/Subspecies
For domestic animals, we have the noun breed, as in breed of dog.
There's not really any objective standard to draw the line between such populations. A clear line exists between populations that cannot reproduce, and there is probably something similar for populations that can reproduce but largely make sterile offspring (Ligers, Mules).