If a ring species existed it would not be an example of observed speciation.
“Justice Oliver Wendell Holmes reportedly said that one good catch-phrase can stop thinking for fifty years. This one certainly has.”
Perhaps many Darwinian biologists take speciation on faith. It’s always someone else who has explained speciation.
Investigators initially thought that a completely reproductively isolated population of polychaete worms had been established in the lab.
TalkOrigins’s section on “The Fruit Fly Literature” is the single longest section of alleged examples of speciation in the FAQ.