Ring species

A ring species is a connected series of neighboring populations, each able to interbreed with the populations next to it along a geographic path, while the populations at the two ends of the chain, where the path loops back on itself, have diverged too far to interbreed with each other. Because the populations in between can interbreed freely while the two ends cannot, a ring species is often used as a real world example of populations gradually diverging into what behave as separate species. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/