Argyrochosma incana

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Argyrochosma incana
Status TNC G5.svg
Secure  (NatureServe) [1]
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Division: Polypodiophyta
Class: Polypodiopsida
Order: Polypodiales
Family: Pteridaceae
Genus: Argyrochosma
Species:
A. incana
Binomial name
Argyrochosma incana
Synonyms
  • Cheilanthes incana(C.Presl) Mickel & Beitel
  • Gymnogramma candida Mett.
  • Hemionitis incana(C.Presl) Christenh.
  • Notholaena incanaC.Presl
  • Pellaea candida(Mett.) Prantl

Argyrochosma incana, the hairy false cloak fern, is a fern known from the southwestern United States through Mexico to Guatemala, and from a disjunct population in the Dominican Republic. It grows on rocky slopes and steep banks, often in forests. Like many of the false cloak ferns, it bears white powder on the underside of its leaves. First described as a species in 1825, it was transferred to the new genus Argyrochosma (the "false cloak ferns") in 1987, recognizing their distinctness from the "cloak ferns" ( Notholaena sensu stricto ).

Contents

Description

Argyrochosma incana is a medium-sized epipetric fern. The rhizome is short, thick, and may be horizontal or somewhat upright. It bears linear to lanceolate [2] or linear-ligulate (straplike) scales [3] 5 to 6 millimeters (0.2 to 0.2 in) long and 0.8 millimeters (0.03 in) wide, without teeth at the margins [2] [4] and long-attenuate at the tip. [3] They are of a uniform dark, shiny brown, [2] chestnut-brown [3] or yellowish-brown color with some dark brown patches. [4] From the rhizome, the fronds arise in clumps. From base to tip of leaf, they are 5 to 20 centimeters (2.0 to 7.9 in) long, [5] sometimes up to 40 centimeters (16 in). [3] Of this length, about half is made up by the stipe (the stalk of the leaf, below the blade), which is shiny and round, hairless, and dark purple to black in color, occasionally chestnut-brown. [2] [4] It is typically 4 to 12 centimeters (1.6 to 4.7 in) in length [4] and 0.75 to 2 millimeters (0.030 to 0.079 in) in diameter. [5]

The leaf blades are deltate (triangular) [2] or lanceolate, [4] tripinnate (cut into pinnae, pinnules and pinnulets) to almost quadripinnate at their bases. They are 3.5 to 8 centimeters (1.4 to 3.1 in) wide, occasionally as little as 2.5 centimeters (0.98 in), [2] obtuse (blunt) at the base and acute (pointed) to acuminate at the tip. [4] The rachis (leaf axis) is round or slightly flattened. [5] The rachis and the axes of the leaf segments are all dark in color; the color stops abruptly at a joint at the base of the leaf segment. [2] Each blade bears 6 to 9 pairs of pinnae, borne oppositely, or nearly so, on the rachis. [2] [3] They are deltate to ovate in shape and borne on long stalks. [3] The ultimate segments of the blade are broadly oblong to ovate [3] or elliptic in shape, 3 to 5 millimeters (0.1 to 0.2 in) long, occasionally as little as 2.5 millimeters (0.098 in), [2] broadly obtuse at their tips and truncate or subcordate (nearly heart-shaped) at their bases. [3] The leaf tissue is grayish-green in color [2] and leathery in texture. [3] [5] The underside of the leaf is coated in white farina (powder), which may be sparsely scattered on the upper surface [2] or absent from it. [3] [5] [6] The leaf axes curl upwards when dry. [4]

The sori lie along the veins, forming a band 0.5 to 1.5 millimeters (0.02 to 0.06 in) wide, [2] occupying from two-thirds to the entire length of the veins. [3] The veins themselves tend to blend into the leaf tissue. [4] The leaf edges are not curved under or modified into false indusia. Each sporangium bears 64 spores. The plants are diploid, with a chromosome number of 2n = 54. [2] [5]

Within the heart of its range, in Mexico, A. incana is both the most widespread member of the genus and the most variable. [7] Some of the characteristics observed to vary are the size of segments (reduced to 2 millimeters (0.08 in) wide), the density of farina on the upper surface, the shape and color of the blade axes (zig-zag rather than straight, and dark purplish rather than black), and the joint at the base of leaf segments (more sharply defined). Material collected in several states of northern Mexico, with small segments, somewhat zig-zag and dark purplish axes may represent an as yet undescribed species. [7] Two specimens collected by C. H. Müller and his wife Mary in Nuevo Leon are anomalous in having chestnut-brown axes and rougher spores, similar to A. delicatula , but their size, abundance of farina below, and lack of it above, led Maxon and Weatherby to classify them as A. incana. [8]

In Mexico, A. incana closely resembles A. delicatula, from which it is distinguished by having white (rather than pale yellow) farina, [9] and A. formosa , which lacks farina. [2] Most specimens in the United States were originally mislabeled as A. limitanea , but this species lacks the joint and abrupt end of dark color at the base of its leaf segments. [10]

Taxonomy

It was first described in 1825 by Carl Borivoj Presl as Notholaena incana, based on material collected by Thaddäus Haenke in Mexico. [11] [12] He did not explain why he chose the species epithet incana, meaning "hoary" (grayish-white). [13] In 1859, Mettenius recognized the genus Gymnogramma for species where sporangia were borne along the nerves and not densely clustered at the end of the nerves. [14] He independently described the species based on material collected by Eugénio Schmitz in Mexico, naming it G. candida. The epithet refers to the chalk-white color of the farina beneath the leaves. [15] [16] Prantl expanded Pellaea to include several genera in which he perceived close affinities, including Gymnogramma. Accordingly, he transferred G. candida to Pellaea section Cincinalis as P. candida in 1882. [17]

William Ralph Maxon and Charles Alfred Weatherby placed N. incana within a group of ferns closely related to Notholaena nivea. [18] Both Edwin Copeland and Weatherby suggested in the 1940s that this group of ferns might represent a distinct genus of its own. [19] This was finally addressed in 1987 by Michael D. Windham, who was carrying out phylogenetic studies of these genera. He elevated Notholaena sect. Argyrochosma to become the genus Argyrochosma , [20] and transferred this species to that genus as A. incana. [21] Meanwhile, John Mickel and Joe Beitel had transferred the species to Cheilanthes as C. incana in their monograph on the ferns of Oaxaca, which was published in 1988; [22] Mickel and Alan R. Smith recognized Argyrochosma in 2004 when preparing a fern flora of Mexico. [2] In 2018, Maarten J. M. Christenhusz transferred the species to Hemionitis as H. incana, as part of a program to consolidate the cheilanthoid ferns into that genus. [23]

While the distinctness of A. delicatula from A. incana has been questioned in the past, [9] phylogenetic studies have upheld the separation of the two taxa. [24] It lies within a subclade of the genus that also contains A. incana, A. pallens, A. peninsularis, A. palmeri, and A. pilifera. All members of the clade share pale farina principally composed of terpenoid compounds, unlike the dihydrostilbenoids found in the farina of other members of the genus. [24]

Distribution and habitat

Argyrochosma incana is known from New Mexico and Arizona [5] [25] south through most of the states of Mexico to Guatemala, [7] and also as a disjunct in the Dominican Republic. [26] David Lellinger reports a specimen (Gómez 7156, CR) collected in Costa Rica, although this occurrence is not mentioned in other floras. [27]

In Mexico, it grows on rocky slopes, banks, and ledges, often shaded or in woods, especially pine-oak forests. It is found at an altitude from 800 to 2,950 meters (2,620 to 9,680 ft). [7] Irving Knobloch reported that material collected from rock crevices in Chihuahua was growing in neutral soils within the crevices. [28] At the northern edge of its range, in the United States, it is found growing from canyon walls, exclusively on igneous rock. [5] In Guatemala, it is found on both shaded and sunny rocks, and growing from rock walls and cliff crevices. [6]

Conservation

Under the NatureServe conservation status system, A. incana is ranked as secure (G5), but it is considered imperiled in Arizona. [1]

Notes and references

Related Research Articles

<i>Argyrochosma</i> Genus of ferns in the family Pteridaceae

Argyrochosma is a genus of ferns known commonly as false cloak ferns. The genus is included in the Cheilanthoideae subfamily of the Pteridaceae. Species now in this genus were previously treated as members of related genera Notholaena or Pellaea but were segregated into their own genus in 1987. These ferns, of which there are about 20 species, are mostly native to the Americas, from North to South and including the Caribbean, while one species, A. connectens, is known from Sichuan, China. They are commonly found growing in cracks between rocks. Their leaves are generally shorter than 40 centimeters and have rounded bluish or grayish green segments. Often the lower surface of the segments is coated in a white dust, and the sporangia contain brown spores.

<i>Argyrochosma jonesii</i> Species of fern in the family Pteridaceae

Argyrochosma jonesii, known as Jones' false cloak fern, is a species of fern native to the southwestern United States and Sonora, Mexico. It grows on calcareous rocks, and has small, finely-divided leaves with a leathery texture and dark axes connecting the leaf segments. Unlike many members of Argyrochosma, it does not secrete white powder on the underside of its leaves. First described as a species in 1917, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

<i>Argyrochosma nivea</i> Species of fern in the family Pteridaceae

Argyrochosma nivea is an Andean fern species in the genus Argyrochosma.

Myriopteris allosuroides is a moderately-sized fern of Mexico, a member of the family Pteridaceae. Unlike many members of its genus, its rachides are grooved on the upper surface and largely free of hairs or scales. One of the cheilanthoid ferns, it was usually classified in the genera Cheilanthes or Pellaea until 2013, when the genus Myriopteris was again recognized as separate from Cheilanthes. It typically grows on dry, rocky slopes over acidic, particularly basaltic, rock.

<i>Argyrochosma dealbata</i> Species of fern in the family Pteridaceae

Argyrochosma dealbata, the powdery false cloak fern, is a small fern endemic to the central and southern United States. It grows on calcareous rocks, such as limestone. Its leaves are highly divided, with leaf segments joined by shiny, chestnut-brown axes, and their undersides are coated with white powder, giving the fern its name. First described as a species in 1814, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

Argyrochosma connectens is a small cheilanthoid fern endemic to Sichuan, China. It is the only member of its genus known from Asia. Relatively rare, it is found growing in the crevices of limestone rocks in hot, dry valleys. The species was long classified in the genus Pellaea, but after a phylogenetic study in 2015 was transferred to Argyrochosma.

Argyrochosma delicatula is a fern known from northeastern Mexico. It grows in rocky habitats, either in sun or in shade, and is distinguished from similar species by the presence of pale yellow powder on the underside of its leaves. First described as a species in 1939, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

<i>Argyrochosma peninsularis</i> Species of fern in the family Pteridaceae

Argyrochosma peninsularis is a fern endemic to Baja California Sur. It grows in dry, rocky places. First described as a species in 1939, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns". A dusting of powdery material and the presence of occasional scales on the central axis of its leaves help distinguish it from related species.

Argyrochosma pallens is a fern endemic to Mexico. It has narrow, divided leaves with brown axes; the leaves are dusted with white powder above and coated in it below. First described as a species in 1956, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

Argyrochosma chilensis is a fern endemic to the Juan Fernández Islands off the coast of Chile. It has leathery, thrice-divided leaves with dark brown axes; the leaves are coated with white powder below. First described as a species in 1853, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

Argyrochosma stuebeliana is a fern endemic to Peru. Its highly divided, leathery leaves are coated with white powder on their under surface. Originally described as a variety of Argyrochosma dealbata in 1909, based on a single leaf collected by Alphons Stübel, whom its name honors, it was recognized as a distinct species in 1961, distinguished from similar members of the genus largely by its round leaf segments. It was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

<i>Myriopteris aurea</i> Species of fern

Myriopteris aurea, the golden lip fern or Bonaire lip fern, is a moderately-sized fern native to the Americas, a member of the family Pteridaceae. Unlike many members of its genus, its leaf is only modestly dissected into lobed leaflets (pinnae), which are hairy both above and below. One of the cheilanthoid ferns, until 2013 it was classified in the genus Cheilanthes as Cheilanthes bonariensis, when the genus Myriopteris was again recognized as separate from Cheilanthes. It typically grows on dry, rocky slopes, and ranges from Mexico, where it is common and widespread, and the southwestern United States south and east through Central and South America as far as Chile and Argentina.

Argyrochosma lumholtzii is a rare fern in the family Pteridaceae known from Sonora, Mexico. It is quite similar to Jones' false cloak fern, but has black leaf axes and a less highly divided leaf. First described as a species in 1939, honoring the explorer Carl Sofus Lumholtz, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

<i>Argyrochosma fendleri</i> Species of fern in the family Pteridaceae

Argyrochosma fendleri, Fendler's false cloak fern, is a fern known from the western United States and northwestern Mexico. It grows in rocky habitats, and is distinguished from other members of the genus by its zig-zag leaf axes. Like many species in the genus, it bears white powder on the underside of its leaves. First described as a species in 1851, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

Argyrochosma palmeri is a fern endemic to Mexico. It has narrow, divided leaves with black axes; the leaves are coated in white powder below, and sparsely dusted or free of it above. First described as a species in 1887, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

Argyrochosma pilifera is a fern endemic to Mexico. It has lance-shaped, divided leaves with dark purple axes; the undersides of the leaves are coated in white powder. First described as a species in 1956, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

<i>Argyrochosma formosa</i> Species of fern in the family Pteridaceae

Argyrochosma formosa is a fern known from eastern and central Mexico and Guatemala. It grows on rocky slopes, particularly on limestone. Unlike many members of the genus, it lacks white powder on the underside of its leaves. First described as a species in 1842, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

<i>Argyrochosma limitanea</i> Species of fern in the family Pteridaceae

Argyrochosma limitanea, the southwestern false cloak fern, is a species of fern native to the southwestern United States and Sonora, Mexico. It grows on calcareous rocks, and has small, finely-divided leaves with a leathery texture, dark axes connecting the leaf segments, and a heavy coating of white powder on the undersurface. It reproduces apogamously; two subspecies are recognized, which may have originated independently through the hybridization of other taxa not yet discovered. First described as a species in 1919, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

<i>Argyrochosma microphylla</i> Species of fern in the family Pteridaceae

Argyrochosma microphylla, the small-leaf false cloak fern, is a species of fern native to New Mexico, Texas and northern Mexico. It grows on limestone rocks and cliffs, and has finely-divided leaves with small leaf segments, often folded in half when dry, which lack the white powder present on the leaf underside of many related species. First described as a species in 1869, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

<i>Myriopteris rufa</i> Species of fern

Myriopteris rufa, commonly known as Eaton's lip fern, is a moderately-sized fern of Mexico and the southwestern United States, with outlying populations in Costa Rica and the Appalachian Mountains. One of the cheilanthoid ferns, it was usually classified in the genus Cheilanthes, as Cheilanthes eatonii, until 2013, when the genus Myriopteris was again recognized as separate from Cheilanthes. It typically grows in rocky habitats, most frequently on limestone but also sometimes on basalt or shale.

References

  1. 1 2 NatureServe 2020.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Mickel & Smith 2004, p. 66.
  3. 1 2 3 4 5 6 7 8 9 10 11 Tryon & Weatherby 1956, p. 92.
  4. 1 2 3 4 5 6 7 8 Lellinger 1985, p. 160.
  5. 1 2 3 4 5 6 7 8 Windham 1993.
  6. 1 2 Stolze 1981, p. 323.
  7. 1 2 3 4 Mickel & Smith 2004, p. 67.
  8. ↑ Maxon & Weatherby 1939, p. 8.
  9. 1 2 Mickel & Smith 2004, p. 65.
  10. ↑ Mickel & Smith 2004, p. 68.
  11. ↑ Presl 1825, p. 19.
  12. ↑ Maxon & Weatherby 1939, pp. 6–7.
  13. ↑ Short & George 2013, p. 192.
  14. ↑ Mettenius 1859, pp. 49–51.
  15. ↑ Short & George 2013, p. 136.
  16. ↑ Mettenius 1859, p. 50.
  17. ↑ Prantl 1882, p. 417.
  18. ↑ Maxon & Weatherby 1939, pp. 3–4.
  19. ↑ Windham 1987, p. 37.
  20. ↑ Windham 1987, p. 38.
  21. ↑ Windham 1987, p. 40.
  22. ↑ Mickel & Beitel 1988, p. 115.
  23. ↑ Christenhusz, Fay & Byng 2018, p. 16.
  24. 1 2 Sigel et al. 2011, p. 561.
  25. ↑ Kartesz 2014.
  26. ↑ Tryon & Weatherby 1956, pp. 92–93.
  27. ↑ Lellinger 1989, p. 121.
  28. ↑ Knobloch 1942, p. 132.

Works cited

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