[waserwill]

Wait till you try to find the boundary between species!

Many plants, and some animals such as birds, can produce fertile hybrids after being separated for millions of years. Especially true for organisms that have reproductive barriers besides genetic and physical incompatibility (different pollinators, geographic separation, birdsong differences, etc).

[Engineering-MD]

Or ring species [0] which is the extension to your example.

[0] https://en.m.wikipedia.org/wiki/Ring_species