Gymnocarpium has ca. 10 species and several hybrids. It occurs mainly in the temperate zones of the N Hemisphere (Asia, Europe, and North America) and subtropical mountains of Asia. The American G. dryopteris is a fertile allotetraploid species that arose from hybridization followed by polyploidization between G. appalachianum Pryer & Haufler and G. disjunctum (Ruprecht) Ching (Pryer & Haufler, Syst. Bot. 18: 150-172. 1993).