Presumably DNA differences - would have been nice to see something about that.
There's mention of wildcats interbreeding with house cats, so presumably ability to cross-breed isn't part of the "new species" calculation?
Considering people have interbred jaguars and leopards, and then interbred the female cubs with lions to get a lijagulep, I'm not sure cross-breeding is the gold standard of speciation that gets sold as such in school.
The greatest threat to some of these cat species (the Scottish Wildcat being a prime example) is loss of genetic differentiation through interbreeding with domestic cats.
> But DNA studies show the cat is actually in a class of its own, highlighting how much remains unknown about some of the world's most elusive mammals.