Asplenium scolopendrium Linnaeus var. americanum (Fernald) Kartesz & Gandhi. Common name: American Hart's-tongue Fern. Phenology: Jul-Sep. Habitat: Limited to humid limestone sinkholes in our region, but also reported as naturalized in a well in MD by Reed (1953). Distribution: E. TN and n. AL, and in other habitats (cool, north-facing, limestone-talus forests) farther north in c. NY, n. MI, and ON; also in the West Indies (Haiti), n. and s. Mexico (CHP, COA, NLE, OAX), and NM (Testo et al. 2021).

Origin/Endemic status: Native

Taxonomy Comments: Heo et al. (2022) studied the "Asplenium scolopendrium complex" with molecular techniques, but did not offer a direct translation of their results into a taxonomy. The complex occurs in three main areas -- 1. Europe and w. Asia, 2. e. and sw. North America, and 3. ne. Asia. These three areas are differentiated by ploidy (1 is diploid, 2 and 3 are autotetraploid) and by haplotypes present (the haplotypes of each region are unique to that region, and also with some unique subgroupings). The disjunct units, poorly differentiated morphologically, have been treated in various taxonomic ways in the past, but most usually and in recent decades as Asplenium scolopendrium (with 2 subspecies) in Europe, A. komarovii Akasawa in ne. Asia, and A. scolopendrium var. americanum in e. North America. Plants in s. Mexico are sometimes treated as entity "lindenii", at varietal or specific rank. The genetic evidence of the overall strong genetic differentiation of the three geographic lineages and their time of divergence in the Pliocene does not support the consensus treatment, which suggests that the Asian plants are the most distinctive, and instead suggests that three species (perhaps with infrataxa) would be appropriate.

Synonymy ⓘ: = FNA2, K4, NS, NY, Tn; = Asplenium scolopendrium L. ssp. americanum (Fernald) N.Heo — Can, POWO, Heo, Yun, & Fernando (2023); = Phyllitis fernaldiana Á.Löve; = Phyllitis scolopendrium (L.) Newman var. americana Fernald — C, F, G, Meso1; < Asplenium komarovii Akasawa — FoC2-3; < Phyllitis scolopendrium (L.) Newman — S13, Sf. Basionym: Phyllitis scolopendrium (L.) Newman var. americana Fernald 1935

Links to other floras: = Asplenium scolopendrium var. americanum - FNA2

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Wetland Indicator Status:

• Eastern Mountains and Piedmont: FACU (taxonomic split from wetland indicator species)
• Northcentral & Northeast: UPL (taxonomic split from wetland indicator species)

Heliophily ⓘ: 1