Myriopteris myriophylla, the Central American lace fern, is a species of lip fern. Despite its common name, this species is native as far south as Argentina. It is adapted to dry areas.
Taxonomy In 1811, Nicaise Auguste Desvaux described two similar species, from Chile and Peru respectively, which he named Cheilanthes elegans and Cheilanthes myriophylla. He distinguished the two on the basis of their scales, reddish in C. elegans and whitish in C. myriophylla. An examination of his type material at the Paris Herbarium in the 20th century by Charles Alfred Weatherby revealed that the type of C. myriophylla is older and the scales have bleached and lost their color. They are in fact essentially identical, and Weatherby chose C. myriophylla as the name to take priority. Both species were (inadvertently) lectotypified to particular specimens in the Desvaux herbarium in 1989. In 1842, John Smith put forth a new generic arrangement of ferns; he transferred C. myriophylla to Notholaena, a genus he characterized in part by long unbroken sori, as N. myriophylla. In the same year, Martin Martens & Henri Guillaume Galeotti described a new species, Cheilanthes paleacea, which they differentiated from C. lendigera on the basis of scale shape. The holotype, collected from the summit of Cuesta Blanca near Metztitlán, is Galeotti 6429 at the Brussels herbarium. A.L.A. Fée's classification of 1852 recognized a new segregate from Cheilanthes, the genus Myriopteris, which he separated from Cheilanthes proper by the presence of hairs among the sporangia and some characteristics of the indusium. He transferred Martens & Galeotti's species there as M. paleacea. Smith accepted Fée's new genus, but also observed that M. paleacea was conspecific with his N. myriophylla. Accordingly, he transferred C. myriophylla to the new genus as M. myriophylla in 1854. In 1857, he (erroneously) identified Fée's M. marsupianthes with Desvaux's C. elegans and transferred the latter to Myriopteris as well as M. elegans. John Gilbert Baker, who with William Jackson Hooker did not recognize Myriopteris, reduced this taxon to a variety in 1867 as C. myriophylla var. elegans. Eugène Pierre Nicolas Fournier described a new species, Myriopteris intermedia, in 1880, which he thought had features resembling both C. lendigera and C. elegans. The syntypes he cited were two collections by J. Guillermo Schaffner, no. 23 from the mountains around San Luis Potosí and no. 24 from the mountains around San Rafael. However, his name was nomenclaturally illegitimate, as it had already been used for a different species by Fée. Baker replaced Fournier's name by transferring it to Cheilanthes as C. intermedia in 1891. Carl Christensen renamed it C. fournieri when he compiled his Index Filicum in 1905, an action now considered nomenclaturally superfluous. Fournier's species was subsequently considered a synonym of C. myriophylla. By a strict application of the principle of priority, Oliver Atkins Farwell transferred C. myriophylla and its var. elegans to the genus Allosorus as A. myriophyllus and A. myriophyllus var. elegans in 1931, that genus having been published before Cheilanthes. Farwell's name was rendered unnecessary when Cheilanthes was conserved over Allosorus in the Paris Code published in 1956. The development of molecular phylogenetic methods showed that the traditional circumscription of Cheilanthes is polyphyletic. Convergent evolution in arid environments is thought to be responsible for widespread homoplasy in the morphological characters traditionally used to classify it and the segregate genera that have sometimes been recognized. On the basis of molecular evidence, Amanda Grusz and Michael D. Windham revived Fée's genus Myriopteris in 2013 for a group of species formerly placed in Cheilanthes. One of these was C. myriophylla, which thus became M. myriophylla again. In 2018, Maarten J. M. Christenhusz transferred the species to Hemionitis as H. myriophylla as part of a program to consolidate the cheilanthoid ferns into that genus. Further molecular studies in Myriopteris demonstrated the existence of three well-supported clades within the genus. M. myriophylla belongs to what Grusz et al. informally named the covillei clade. Members of the "core covillei" clade, including M. myriophylla, have leaves finely divided into bead-like segments. Within this clade, M. myriophylla is part of a subclade including M. chipinquensis, M. jamaicensis, M. rufa, M. tomentosa, and M. windhamii, most of which are apogamous.
Conservation NatureServe considers it globally secure (G5), but vulnerable (S3) in Florida, at the northern end of its range.
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External links Type specimen of Cheilanthes myriophylla Type specimen of Cheilanthes elegans Type specimen of Cheilanthes paleacea Type specimen of Myriopteris intermedia E.Fourn.
