For example, an animal moves from the tropics to the arctic. It adapts overtime …

Assuming it survives to adapt. Less fit to me means less likely to survive. And it is unclear to me how yeast would naturally separate themselves into the appropriate populations in separate environments to achieve the advantage you claim

The pre-existing systems aren't lost. They have been modified…

You are not talking about the same thing. This is not something that you could determine from the research. Behe stated (his most important point IMHO which you didn't address) "The authors did not analyze the genetic changes that occurred in the cells"

The fact is, neither you nor Behe nor anyone else knows what happened genetically. Behe surmizes that it falls into the well-defined range of possible changes that RM+NS has beeen demonstrated to accomplish.

Now maybe Behe is wrong about that, but you can't claim to know it.