system
A chat on subreddit /r/me_irl
human
The only thing they've really been selectively bred for is the color; even then you still see a lot of natural colored individuals. 

The real issue is they've crossed them with Tiger Salamanders. This is why you'll see some of them fully morph into salamanders because they aren't full axolotls.
gpt
Axolotls are salamanders that do not go through metamorphosis when they become adults in the wild unless they are put under high levels of stress.