''Polypodium appalachianum'' is a

fern The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...

species native to eastern North America. Sometimes called the Appalachian polypody or Appalachian rockcap fern, it is very similar in appearance to '' Polypodium virginianum''. 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. The name is derived from Greek ''poly-'' ("many") and ''pous, podos'' ("foot"). Polypody has traditional uses in cooking for its aroma and sweet t ...

''—was recognized as having cryptic races, with

diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Here ''sets of chromosomes'' refers to the number of maternal and paternal chromosome copies, ...

triploid Polyploidy is a condition in which the cells of an organism have more than two paired sets of ( homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two complete sets of chromosomes, one fro ...

, and

tetraploid Polyploidy is a condition in which the cells of an organism have more than two paired sets of ( homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two complete sets of chromosomes, one fro ...

representatives. Since the triploid specimens bore abortive spores, it was apparently the

hybrid Hybrid may refer to: Science * Hybrid (biology), an offspring resulting from cross-breeding ** Hybrid grape, grape varieties produced by cross-breeding two ''Vitis'' species ** Hybridity, the property of a hybrid plant which is a union of two diff ...

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 Polyploidy is a condition in which the cells of an organism have more than two paired sets of ( homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two complete sets of chromosomes, one fro ...

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''. 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''. ''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 a plant or plant-like organism that grows on the surface of another 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 epiphyt ...

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 The Appalachian Mountains, ...

. 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 A colony is a territory subject to a form of foreign rule, which rules the territory and its indigenous peoples separated from the foreign rulers, the colonizer, and their '' metropole'' (or "mother country"). This separated rule was often or ...

, forming dense mats that hold

organic matter Organic matter, organic material or natural organic matter is the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have come fro ...

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