You're automatically assuming microevolution has a cut off point. On what grounds do you base this on?
our experience as humans. We have never seen anything beyond simple variation.
I have used this example before, but we have been working with E.coli for over a hundred years now. With a 20 minute generation time, this easily goes over 2.5 million linear generations. We have thrown every mutagent in the book -- and then a few -- at them. In 2.5 MILLION geneerations we have not seen any variation outside the realm of E.coli. We have had some fat E.coli, and we even had one strain that was able to develop a new internal pathway when scientists removed some rather essential elements in the old pathway, but mostly we have only had dead E.coli. We have NEVER, in all those tries and all those generations, seen anything from this tiny prokaryote that was not an E.coli.
If two-and-a-half million generations of a simple one-celled prokaryote cannot give us any decent changes no matter what we do, the time argument for other organisms seems to be in a precarious state. I keep hearing, "but it takes time!" And I would ask, "OK, how many generations?"
Very simply, no matter whether it is organisms with a long generation time, such as mammals, or a short generation time, such as bacteria, we have NEVER seen a change outside of simple variation.
So, in answer to your question, I would respond
"extant evidence"