DAVID: Despite not finding genetic changes, this suggests that there are epigenetic influences of some sort, and that normally living monarchs contain instructions they must follow.

dhw: I would suggest that this suggests that epigenetic influences were the original spur to the pattern of migration, and when the environment was changed, the monarch changed its responses accordingly. Once a system is successful, it is passed on and will survive until conditions change. Then the organism will either change to fit in with new conditions, or it will perish. The process is known as evolution.

Have you forgotten that evolution requires speciation? This is simply adaptation.