[b_sharp]

Do the terminal subspecies of a ring species not fit the definition of sympatric speciation? They generally inhabit the same geographical area.

[VadeRetro]

The overlapping ends are in the same area, but I'd say the speciation was allopatric. It is caused by differences of adaptation and history enforced by considerable if not total geographic isolation up until the ends reunite.

Also, there really aren't that many instances of ring species, so even if you count them as sympatric there still aren't many sympatrics.