they studied are instances in which animals with the same genetic makeup can produce quite different traits, or phenotypes, in different environments.
You're misreading the passage, although admittedly it's not as clear as it could be. It's not saying that the evolved versions had the "same genetic makeup" as the originals, it's saying that the evolved version was situationally able to produce two different traits out of the same (new) genetic code.
I'm quite curious as to what this "new genetic code" might be?
Perhaps aug is now a stop codon?