Isolation does *not* lead to speciation. If it did, then pigeons in New York would be different from pigeons in Australia.
And “ring species” are no such thing...just the same species in different colors.
A pigeon is just a pigeon, and it is well known that they are all exactly alike. (Except, of course, when they're not: Dove & Pigeon Species Listing)
And “ring species” are no such thing...just the same species in different colors.
You should publish this. You'll be famous.