Meniscium
Creators: name: Fawcett, Susan
name: Smith, Alan R.
Publisher: name: BRIT Press
Year: 2021
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Polypodiopsida
Polypodiales
Thelypteridaceae
Meniscium

description: MENISCIUM
Meniscium Schreber, Gen. Pl., ed. 8 (a), 2:757. 1791.— Thelypteris subg. Meniscium (Schreber) C.F.Reed
— Type: Meniscium reticulatum (L.) Sw.[= Polypodium reticulatum L.]
For additional synonymy see Fernandes (2020).
Etymology.—Gr. meniskos, moon, in reference to the lunulate (crescent-moon shaped) sori that characterize this genus; these are coalescent or continuous along the arching cross-veins, which produce an excurrent vein at their union. This contrasts with Goniopteris, in which the discrete round sori are in pairs on the cross veins, on both sides of the origin of the excurrent veinlet, where the anastomosing cross-veins meet at an often acute angle.
Plants terrestrial, rarely rheophytic, medium-sized (ca. 50 cm) to very large (> 2 m); rhizomes short-creeping, sometimes ascending, thick, nearly scaleless back from the tip; fronds monomorphic or weakly dimorphic (fertile pinnae narrower and more densely hairy than sterile ones), infrequently fully dimorphic (if so, sporangia appearing acrostichoid at frond maturity), simple to usually 1-pinnate, erect or arching; stipes stramineous, dull brown, or rarely castaneous (Meniscium giganteum); stipe scales dull brown, broadly ovate-deltate to ovate-lanceolate, often abraded in mature fronds; blades chartaceous to subcoriaceous, laminae typically drying greenish; pinnae adaxially grooved, entire, crenate, or infrequently serrate (M.consobrinum; M.serratum), never lobed, proximal pinnae not or little reduced, distal pinnae gradually to often abruptly reduced, usually with a conform or subconform apex; buds often present in axil of a proximal pinna; veins regularly anastomosing, forming parallel rows of areoles, with (3–)10–25 pairs united and forming areoles; cross veins straight, arcuate, or subsigmoid, giving rise to excurrent veins that are generally free, but sometimes continuous and straight from one areole to the next; aerophores absent at pinna bases; indument abaxially lacking, sparse, or occasionally dense, of hyaline acicular, often curved hairs, generally restricted to costae, costules, and veins, less often on laminar tissue between veins, rarely of stipitate glands, scales lacking on costae; indument adaxially absent or of hyaline acicular hairs usually restricted to costae; pustules absent on laminar tissue abaxially and adaxially; sori along cross-veins, often coalescent and so oblong, linear, or lunate, mostly in single rows between main lateral veins, occasionally discrete and round or nearly round and forming two rows between main lateral veins (e.g., M. lingulatum), always exindusiate; sporangia usually without setulae (except in M. macrophyllum) or glands, but with setae or stalked red to orange spherical glands sometimes borne on sporangial stalks; receptacles bearing stalked, tubular, orangish glands in a few species (M. andreanum, M. arcanum); spores typically black or dark brown, perispore winged, the wings echinulate or fimbriate (Tryon & Lugardon 1991; Fernandes et al. 2014; Patel et al. 2019a); x = 36, 2 n = 72 (M. serratum), 144 (M. reticulatum), only two of 25 spp. counted. No intrageneric or intergeneric hybrids are known.
Diagnosis.— A few New World species with meniscioid venation are herein treated in Goniopteris (e.g., G. clypeata, G. mollis, G. holodictya, G. liebmannii, G. poiteana). Meniscium can be readily distinguished from Goniopteris by the lack of stellate or furcate hairs on the rhizome and stipe base scales, as well as on the blades, by the usually much greater number of areoles between the costae and pinna margins, by the sori usually arcuate, linear, or confluent at maturity (vs. sori round and in two discrete rows between main lateral veins in Goniopteris), by the usually 1-pinnate blades with entire, crenate or serrate, unlobed pinnae, and by the usually much larger frond size.
Biogeography and ecology.—The majority of the 26 species of Meniscium are either exclusively South American or largely South American with range extensions into Mesoamerica and/or the Antilles, and most occur in Andean countries, the center of diversity for the genus; M. cocleanum, M. falcatum, and M. turrialbae in Mesoamerica and M. reticulatum in the Antilles are the major exceptions to this pattern. The range of the genus is from peninsular Florida, the Antilles, and southern Mexico to Bolivia, southern Brazil, Paraguay, and northern Argentina, almost exactly the range of M. serratum, one of the more common and most widespread species in the genus. Most species of Meniscium tend to be widespread, but a few are narrow endemics (e.g., M.cocleanum, M.consobrinum). They are confined to low and middle elevations, from 0–1500(–2000) m, and are found along streams, in wet forests, and ditches. At least one, M. serratum, often occupies marshes and swamps, in open or partially open habitats.
Taxonomic and phylogenetic studies.—The species were first revised by Christensen (1913), later by Maxon and Morton (1938), and most recently by Fernandes (2020). The last author and coauthors (Fernandes et al. 2014; Fernandes & Salino 2016) described several new species (increasing the total to 26) and provided a key to the Brazilian species. Smith and Kessler (2017) treated the 13 Bolivian species.
Meniscium is monophyletic in all major phylogenetic studies (Almeida et al. 2016; Fawcett et al. in press) and is sister to a clade including Ampelopteris, Mesophlebion, and Cyclosorus s.s., the first two of these paleotropical, the last pantropical. Holttum (1982) postulated a relationship among all three of these last genera, but not to Meniscium. Goniopteris is, in turn, sister to this combined 4-genus clade (Fawcett et al. in press). All five genera are sister to a huge clade comprising the remaining cyclosoroid genera (which includes Pronephrium s.l.) Thus, the so-called “meniscioid” venation in Meniscium, Menisciopsis, Goniopteris, Pronephrium, and a few other cyclosoroid genera appears to have evolved many times, independently.
Miocene deposits including a fossil Meniscium have recently been found in Colombia (SanÍn et al. 2016); assignment of this fossil to an extant genus is likely correct based on venation and geographic location. The date of the fossil falls well within divergence estimates of the genus published by Testo and Sundue (2016).
Several genera here segregated from the Old World genus Pronephrium bear some resemblance to Meniscium in having large, one-pinnate fronds with many pairs of anastomosing veins between the costae and pinna margins. Several species in these genera have historically been included in Meniscium because of this similarity, but these are now treated in Grypothrix, Pronephrium, Abacopteris, or Menisciopsis. From Grypothrix, which sometimes mimics Meniscium in venation, Meniscium differs in lacking hamate hairs on the blades. Abacopteris differs in having setulose sporangia, and medial, discrete, round sori. Pronephrium differs in having more strongly dimorphic fronds, much smaller frond size, frond apex gradually reduced (non-conform), and sometimes yellow glands on indusia and/or laminae. Menisciopsis differs in typically having discrete sori, which may be indusiate. Meniscium generally differs from all of these in the frequent presence of proliferous buds in axils of proximal pinnae (though these are present in some Grypothrix), sori generally coalescent or continuous along arching or straight cross-veins, and usually by the much greater number of areoles between costae and pinna margins. Meniscium is strictly neotropical, whereas all of the genera segregated from Pronephrium are paleotropical.
Constituent species.—* Meniscium andreanum Sodiro; * M. angustifolium Willd.; * M. arborescens Humb. & Bonpl. ex Willd.; * M.arcanum (Maxon & C.V. Morton) Pic.Serm.; * M. chrysodioides Fée; M. cocleanum (A.R. Sm. & Lellinger) R.S. Fern. & Salino; * M. consobrinum (Maxon & C.V. Morton) Pic.Serm.; * M. delicatum R.S. Fern. & Salino; M.divergens R.S. Fern. & Salino; * M. falcatum Liebm.; * M. giganteum Mett.; * M. hostmannii (Klotzsch) R.S. Fern. & Salino; * M. lanceum (A.R. Sm.) R.S. Fern. & Salino; * M. lingulatum (C. Chr.) Pic.Serm.; * M. longifolium Desv.; * M. macrophyllum Kunze; * M. maxonianum (A.R. Sm.) R.S. Fern. & Salino; * M. membranaceum (Mett.) Pic.Serm.; M. minusculum (Maxon) Pic.Serm.; * M. nesioticum (Maxon & C.V. Morton) Jermy & T.G. Walker; * M. pachysorum (Hieron.) R.S. Fern. & Salino; * M. reticulatum (L.) Sw.; * M.serratum Cav.; M. standleyi (Maxon & C.V. Morton) Pic.Serm.; M.triangularis R.S. Fern. & Salino; M. turrialbae (Rosenst.) Pic.Serm. Several species described in Meniscium in the Neotropics are heterotypic synonyms of species accepted above.
description: Published as part of Fawcett, Susan & Smith, Alan R., 2021, A Generic Classification of the Thelypteridaceae, Fort Worth, Texas, USA :BRIT Press on pages 53-54, DOI: 10.17348/jbrit.v15.i2.1206, http://zenodo.org/record/14111022