Ensatina salamanders are the classic example of a ring species in evolutionary biology.
Ensatina is a group of closely related salamanders found around California’s Central Valley. Populations spread around the valley’s dry interior, forming a geographic ring. Neighboring populations can generally interbreed, but the two populations meeting at the southern end of the ring are reproductively isolated.
This arrangement illustrates how gradual divergence can accumulate across a geographic range. It also helps scientists study the difficult boundary between variation within a species and the formation of separate species.
The example is often simplified in textbooks, and researchers continue to debate how strictly the term “ring species” applies to Ensatina. It is therefore better described as a classic case study rather than an uncomplicated model. The salamanders are still valuable for showing how geography, gene flow, and local adaptation can interact during speciation.