The question is why would it occur in the conditions you proposed.
Speciation has occured many times, in plants and animals, in the examples I provided.
Just because you don't like the facts don't quibble with the definition of speciation. By the standard defitinion speciation has occured.
John you need to update your biology education. A breed like in dogs can fertilize any other breed of dogs. Fertilization of an Irish Wolfhound by a Yorkie will occur.
Fertilization of these species does not occur. It's why they are different species. They are ot different breeds.
Many species have encountered and evolutionary dead end, this does not negate the fact that evolution has occured. So objection polyploidy as evolution is not valid.
"As for Darwin predicting DNA" -- no I am not kidding. Try reading it again.