ring species

Noun

 * 1) A biological species consisting of overlapping subgroups, each of which can interbreed with the next, but which cannot freely interbreed when taken as a whole
 * Ring species demonstrate that "can interbreed with" is not transitive.

Translations

 * Finnish: rengaslaji
 * German: Artenkreis, Rassenkreis, Ringspezies