They won't be. Anything the Ancients moved will be noticeably and genetically distinct.
I don't understand how you can say that with such uncompromising certainty. As I understand it, the last subspecies of any of the
Panthera to diverge, the American lion, did so 340,000 years ago, before the Ancients did their thing. The last divergence into separate species (lion and leopard) was 800,000 years ago.
If you had said that populations transplanted to other worlds would be
more likely to diverge (due to environmental pressures of strange new habitats), then I'd agree. But surely the evidence I just quoted shows that it is perfectly possible for a population of
Panthera to remain substantially the same for much longer than 300,000 years.
Each world may have 1-5 new species, and yet may remain genus Pantera.
I wouldn't even contemplate divergences large enough to create separate genera in just 300,000 years. Though I haven't actually checked on how fast mammals can diverge that far, so I could be wrong there.
For naming them, well, might I point out that a lot of unrelated species have wound up with (Locative) (species) format names. Such as the Horseshoe Crab vs the other crabs - far less related than crab and shrimp are, but more obviously similar in appearance.
And I fully intend to make use of that sort of name. One reason for my question about canonical worlds with terrestrial flora and fauna. I expect I'll have to come up with a goodly numer of non-canon[*] worlds like that by myself, but I don't want to miss the one or two that has already been established.
[*] But canon-compatible. 
And the "Tasmanian Tiger" wasn't even a placental... but a Thylacine. And the hundreds of species of Duck are mostly named for regions. Similar for Geese.
And the alien vaguely felinoid species that I intend to come up with wouldn't even be the same sphere.
So, except where really wide divergence into absent niches happened, lots of species will be commonly called "___ Lion" "___ Tiger" or "___ Panther"... and most of them on transplanted menageries worlds will still have one or more subspecies in the original niche... and thus Terrans are likely to call them lions, tigers, and panthers.
Possibly. Possibly not. On Earth separate species of great cats have distinct names. All the ones called "_____ Lion" and "_____ Tiger" and so on are subspecies. So I'd still like to come up with some distinct one-word species names. Unfortunately, I haven't had any luck so far.
For the ones that are known primarily by Vilani names, again, it's likely to be based upon the names for any big cats which were close to Vland‡.
That's a very good point. For new hitherto unknown species Terran taxonomers could easily turn to the Vilani names.
"This great cat diverged from the Sylean Lion some 250,000 years ago, but it's definitely a distinct species by now. What did you say it was called? Kaadshanashkhaa? Bit of a jawbreaker that. We'll call it a kashan. Taxonomic name: Panthera kashan
. That'll do.
And those are likely to be named for the local Vilani analogues, again by (Locative) (Prototype). So, pick a random number of species names, generate the prototype pouncer's names, and then apply a zillion locatives.
Well, I do want a tiny bit of originality too.
Same process for other significant languages.
Some fun can also be had by using non-english Terran names.
Just hitting translate.google.com and copying the transliteration below the translation....
Language | "The Panther" | "The Tiger" | "The Lion" |
Japanese | Hyō | Taigā | Raion. |
Ukrainian | Pantera | Tyhr | Lev . |
Byelorussian | Pantera | Tyhr | Lieŭ . |
Hmong | Lub tus tsov dub. | Tus Tsov. | Tus Tsov Ntxhuav. |
Thai | Phæn the xr̒ | S̄eụ̄x | S̄ingto |
Thank you for your effort, but I feel that if I start down that road, I could probably name all 200+
Tigresses just from Earth alone, and what would be the fun of that?
‡ If there had been significant numbers of introduced species besides the humans on Vland, the Vilani would have had a far better theory of diseases. Humans seem to be the only macrobiotic terran life described as being on Vland...
Agreed. I don't plan to introduce any Vlandian lions or tigers or bears.
Hans