[ihartley]

If anyone else is curious, this is called a ring species, and there are only four known examples: https://en.wikipedia.org/wiki/Ring_species

[delhanty]

>non-breeding, though genetically connected, "end" populations may co-exist in the same region

This reminds me of the Riemann surface associated with the complex logarithm:

https://en.wikipedia.org/wiki/Complex_logarithm#The_associat...