Why are ring species interesting?

Ring species can provide important evidence for evolution, because they show that intra-specific differences can be large enough to produce an inter-species difference. The differences between species are therefore the same in kind (though not in degree) as the differences between individuals, and populations, within a species.

Boundaries between species become fluid

A supporter of the theory of separate creation might argue that although individuals do vary within a species, nevertheless that variation is too limited ever to give rise to a new species: the origin of new species is then not a magnified extension of the kind of variation we see within a species. But in ring species the extremes meet, and we can see that they form two species. It is then almost impossible to deny that natural variation can be large enough to generate new species.

Ring species, therefore, show that there is a continuum from interindividual to inter-species variation. Natural variation is sufficient to break down the idea of a distinct species boundary. The same argument can be applied to larger groups than species, and by extension to all life. The idea that nature comes in discrete groups, with no variation between, is a naive perception. If the full range of natural forms, in time and space, is studied, all the apparent boundaries become fluid.