Asplenium quadrivalens (D.E. Meyer) Landolt. Maidenhair Spleenwort. Phen: May-Oct. Hab: Moist outcrops of calcareous sedimentary rocks, such as limestone or dolostone. Dist: A. quadrivalens is known from North America and Eurasia (at least); in North America it is substantially rarer than diploid A. trichomanes and more limited in range, occurring from New England, s. ON, and AK south to w. VA, OH, and s. IL, and in BC, WA, and OR.

Origin/Endemic status: Native

Other Comments: A. quadrivalens is the result of the hybridization of two ecologically differentiated diploid taxa in the A. trichomanes complex. It is possible that future research will determine that two or more taxa (with different alloploid parental origins) are present within what is here treated as a single taxon at species rank.

Synonymy: = FoC2-3; = Asplenium trichomanes L. ssp. quadrivalens D.E.Mey. – FNA2, Il, K1, K3, K4, NE, NY, Pa, Va, W; < Asplenium trichomanes L. – C, F, G, GrPl, RAB, S13, Sf

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Wetland Indicator Status:

• Eastern Mountains and Piedmont: FAC (taxonomic split from wetland indicator species)
• Great Plains: FAC (taxonomic split from wetland indicator species)
• Midwest: UPL (taxonomic split from wetland indicator species)
• Northcentral & Northeast: UPL (taxonomic split from wetland indicator species)

Heliophily: 1