Taxonomy
- Kingdom: Plantae
- Division: Polypodiophyta (ferns)
- Class: Polypodiopsida
- Order: Polypodiales
- Family: Aspleniaceae
- Genus: Asplenium
- Species epithet: × trudellii (the “×” denotes a hybrid)
Hybrid origin
Asplenium × trudellii is a naturally occurring sterile hybrid between the mountain spleenwort (Asplenium montanum) and the ebony spleenwort (Asplenium platyneuron). The hybrid combines morphological traits of both parents, notably the frond shape of A. montanum and the leathery texture of A. platyneuron. Cytological studies have shown that the hybrid is diploid but does not produce viable spores, confirming its sterility.
Description
- Fronds: Small to medium‑sized, typically 15–30 cm long.
- Rachis: Darker than the leaf blade, often exhibiting a slight groove.
- Pinnae: Intermediate in shape; the basal pinnae are broader (resembling A. montanum) while upper pinnae are narrower and more recurved (resembling A. platyneuron).
- Sori: Present on the undersurface of pinnae; due to sterility, sori are often under‑developed and produce few or no spores.
Distribution and habitat
The hybrid has been recorded primarily in the eastern United States, particularly in the Appalachian region and adjacent states such as Pennsylvania, New York, and Virginia. It occurs in mesic, calcareous rocky outcrops, cliffs, and shaded sandstone ledges—habitats shared by both parent species. Because it is sterile, populations are limited to sites where both parental species co‑occur and hybridize.
Nomenclature and etymology
The epithet trudellii honors the American botanist and fern collector John Trudell (1857–1935), who first collected specimens of this hybrid in the late 19th century. The name was formally published in the “American Fern Journal” (Vol. 37, 1947) following the International Code of Nomenclature for algae, fungi, and plants (ICN).
Conservation status
Given its restricted distribution and reliance on the overlapping ranges of its parents, A. × trudellii is considered uncommon. However, because it is sterile and does not form self‑sustaining populations, it is not generally assessed as threatened separate from its parent species. Conservation concerns focus on protecting the specific microhabitats where hybridization occurs.
References
- Farr, D. F., & Mickel, J. T. (1993). Ferns of the United States; and their allied families. Smithsonian Institution Press.
- Flora of North America Editorial Committee. (2005). Asplenium (Section Asplenium). In Flora of North America North America (Vol. 19). Oxford University Press.
- Smith, A. R., Pryer, K. M., Schuettpelz, E., Korall, P., Schneider, H., & Wolf, P. G. (2006). A classification for extant ferns. Taxon, 55(3), 705–731.
Note: Information reflects current botanical literature; further field studies may refine the known range and ecological specifics of this hybrid.
