''Polypodium appalachianum'' is a fern species native to eastern North America. Sometimes called the Appalachian polypody or Appalachian rockcap fern, it is very similar in appearance to ''

Polypodium virginianum ''Polypodium virginianum'', commonly known as rock polypody, rock cap fern, or common polypody, is a small evergreen species of fern native to the Eastern United States and Canada. It generally grows on rocks and occasionally on tree roots in nat ...

''. For years, ''P. virginianum''—long considered a variety of the British ''

Polypodium vulgare ''Polypodium vulgare'', the common polypody, is an evergreen fern of the family Polypodiaceae. ''Polypodium vulgare'' is an allotetraploid species, believed to have arisen by chromosome doubling of a sterile diploid hybrid between two ferns which ...

''—was recognized as having cryptic races, with diploid, triploid, and tetraploid representatives. Since the triploid specimens bore abortive spores, it was apparently the hybrid between the diploid and tetraploid groups. In 1991, it was resolved that the type of ''P. virginianum'' was the tetraploid series, and that it is an allotetraploid species of hybrid origin, with the diploid species as one parent. The diploid species was then named ''P. appalachianum''. The other parent of ''P. virginianum'' was found to be ''

Polypodium sibiricum ''Polypodium'' is a genus of ferns in the family Polypodiaceae, subfamily Polypodioideae, according to the Pteridophyte Phylogeny Group classification of 2016 (PPG I). The genus is widely distributed throughout the world, with the highest s ...

''. The tetraploid of hybrid derivation tolerates warmer climates than either parent. ''Polypodium sibiricum'' is also now known to be one of the parents of the allotetraploid ''

'', along with ''

Polypodium glycyrrhiza ''Polypodium glycyrrhiza'', commonly known as licorice fern, many-footed fern, and sweet root, is a summer deciduous fern native to western North America, where it is found in shaded, damp locations. Spores are located in rounded sori on the u ...

''. ''P. appalachianum'' is an epipetric plant, preferring sandstone or other hard, noncalcareous rocks. However, it is known to grow as an

epiphyte An epiphyte is an organism that grows on the surface of a plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphytes grow are called phoroph ...

in the

Smoky Mountains The Great Smoky Mountains (, ''Equa Dutsusdu Dodalv'') are a mountain range rising along the Tennessee– North Carolina border in the southeastern United States. They are a subrange of the Appalachian Mountains, and form part of the Blue Ri ...

. Throughout much of its range, it will be found to grow in places more sheltered from the sun and heat than is ''P. virginianum''. Both species, and their hybrid, can form large clonal colonies, forming dense mats that hold organic matter in place on rock shelves and surfaces.

References

*USDA Plants Profile of ''Polypodium appalachianum''

*Flora of North America entry for ''Polypodium appalachianum''

*Species citation: American Fern Journal volume 81, number 1, page 18, 1991. JStor reference

*''Polypodium appalachianum'' as epiphyte in the Smoky Mountains: American Fern Journal volume 93, number 1, pages 36–41, 2003. JStor reference

External links

* {{Taxonbar, from=Q7226720 Polypodium, appalachianum Ferns of the Americas Ferns of the United States Flora of Eastern Canada Flora of the Eastern United States Epiphytes Plants described in 1991