Macrothelypteris

Fawcett, Susan & Smith, Alan R., 2021, A Generic Classification of the Thelypteridaceae, Fort Worth, Texas, USA: BRIT Press : 50-52

publication ID	https://doi.org/ 10.17348/jbrit.v15.i2.1206
DOI	https://doi.org/10.5281/zenodo.14076472
persistent identifier	https://treatment.plazi.org/id/03B787F6-FFD5-9B75-622B-78B3FC5FFD4C
treatment provided by	Donat
scientific name	Macrothelypteris
status

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MACROTHELYPTERIS View in CoL

Macrothelypteris (H. Ito) Ching, Acta Phytotax. Sin. View in CoL 8:308. 1963.

— TYPE: Macrothelypteris oligophlebia (Baker) Ching View in CoL [= Nephrodium oligophlebium Baker View in CoL ]

For additional generic synonymy, see Holttum,1969, 1971.

Etymology. —Gr. makros, large + Thelypteris . This genus has some of the largest and most deeply dissected (tripinnate-pinnatifid) fronds in the family.

Plants terrestrial, fronds of determinate growth, mostly medium-sized to very large, 50–200+ cm tall; rhizomes short-creeping to ascending or suberect, to 1 cm diam., with brown to tan scales, these lanceolate, with scattered hairs along margins and sometimes sparingly on surface; fronds clustered, monomorphic, evergreen or dying in winter ( M. viridifrons ); stipes to 80 cm long, 12 mm diam., not grooved adaxially, green or stramineous, less often castaneous (e.g., M. ogasawarensis ), sometimes glaucous (e.g., M. torresiana ); stipe scales lanceolate, stramineous to brown, 2–20 mm long, thickened at their bases, usually with a hairlike tip, typically with marginal and superficial hairs and often with stipitate glands ( Fig. 2G View FIG ); blades herbaceous to chartaceous, broadly deltate, to 1 m long, usually broadest at bases or with proximal pinnae only slightly reduced (always lacking greatly reduced glanduliform pinnae), lacking buds or proliferations, pinnate-pinnatifid to bipinnate- or even tripinnate-pinnatifid, with blade apex gradually tapering and pinnatifid; rachises adaxially not grooved, bearing simple acicular, often septate hairs, sometimes with persistent scales that leave a stump or “wart” when breaking off (e.g., M. banaensis , M. multiseta , M. ornata , M. setigera ); pinnae to 15–35cm, subopposite proximally to alternate distally, subsessile or stalked, distal pinnae increasingly adnate, spreading or obliquely spreading, not grooved adaxially, truncate at bases, acute at tips, to ca. 15(–20) × 2(–3) cm wide, pinnatifid or pinnate-pinnatifid with pinnules adnate and sometimes interconnected at their bases, in larger species free, with or without acroscopic and/or basiscopic, more lobed basal auricles, sessile or nearly so; veins free, often forking in ultimate segments, ± easily visible on both sides, vein ends clavate adaxially and not reaching segment margins; aerophores absent at pinna bases; indument abaxially usually of sparse to moderately dense unicellular or often septate hyaline acicular hairs 0.5– 2 mm long, in some species also with costal scales (e.g., M. ornata , M. setigera ), blades often glabrescent with age, short-stipitate pale yellowish glands sometimes present along costae and costules; indument adaxially of hyaline acicular hairs to ca. 1 mm long along costae, sometimes also with hairs and stalked glands on costules and ultimate veins, occasionally on laminar tissue between veins; pustules absent on laminae between veins; sori medial to supramedial, round, exindusiate ( M. ornata ) or usually with small indusia to ca. 0.3 mm diam. (often hidden in mature sori), sori not confluent at maturity; sporangia glabrous or with 1–3 short-stipitate glands ca. 0.05 mm long adjacent to annulus on capsule, sporangial stalks short; spores tan to brown, ± winged or with a fine reticulate network, but lacking a low polygonal network of ridges as in Pseudophegopteris . Perforations in the perine (resembling those of the distantly related Amauropelta , but generally coarser) characterize the genus (although lacking in M. viridifrons ), and distinguish it from other Phegopteridoideae ( Holttum 1969; Tryon & Lugardon 1991; Patel et al. 2019a). x = 31, diploids, triploids, and tetraploids known, with five spp. counted. No hybridization with any other genus has been demonstrated.

Diagnosis.— Macrothelypteris is most closely related to both Pseudophegopteris and Phegopteris , which all share the characteristic of lacking grooves along the rachis and costae adaxially. This separates them from all other genera of Thelypteridaceae , except Metathelypteris and some Leptogramma , both of which are generally much smaller plants than Macrothelypteris . The conspicuous septate hairs, more alternate pinnae, and usually indusiate sori easily separate Macrothelypteris from Pseudophegopteris . Phegopteris is a genus of temperate, and high tropical montane environments, not occurring with Macrothelypteris , and has medial pinnae adnate to rachis (vs. mostly free). Tryon and Lugardon (1991) photographed spores of four species of Macrothelypteris . Spores of M. polypodioides and M. setigera ( Tryon & Lugardon 1991; figs. 151.1–151.4, respectively) are similar and show a fine reticulate perispore, somewhat similar to spores of many neotropical Amauropelta spp. , e.g., A. concinna (fig. 149.5); spores of M. ornata and M. torresiana (figs. 152.5, 152.7, respectively) have coarser, irregular folds, with small perforations, more like those of the Asian amauropeltoids (fig. 149.16). Even considering this variation, and incomplete sampling, Macrothelypteris appears to be readily differentiated from both Phegopteris and Pseudophegopteris based on spore morphology.

Biogeography and ecology.— Macrothelypteris comprises about 10 species, which are confined to Madagascar and the Mascarene Islands in the Indian Ocean, India, and continental eastern Asia, Australia, Malesia, Melanesia, and Polynesia (to the Society and Austral Islands; Holttum 1969). A single species, M. torresiana , is widely introduced and abundantly naturalized in the New World tropics and subtropics, extending from South Carolina and Arkansas to Florida and Louisiana ( Leonard 1972; Smith 1993a), southward into the Antilles, southern Mexico, and Central America, and further south through much of South America to northern Argentina and Bolivia; it is also naturalized in Natal, South Africa ( Burrows 1990), Hawai’i ( Palmer 2003), and perhaps elsewhere. The greatest diversity in the genus is in China, with six species (but only one endemic, M. contingens ), one with two varieties ( Lin et al. 2013). Species of Macrothelypteris occur mainly in forests (but not in deep shade) or along forest margins, along trails and streams, and in shaded wet places, often in areas with some sun or in disturbed areas, at low to middle elevations from 0–2100 m.

Taxonomic and phylogenetic studies. —Both Macrothelypteris and Pseudophegopteris were first recognized at generic rank by Ching (1963). Holttum’s studies further clarified their distinction and differences ( Holttum 1969, 1971, 1974a, 1977b, 1982). See comments under Pseudophegopteris for distinctions between the two genera. These two genera have retained their rank in publications on the family by Smith (1990), Smith et al. (2006), and in PPG I (2016), as well as in many recent floras.

In our analyses (Fawcett et al. in press), and also those of He and Zhang (2012), Schneider et al. (2013), and Almeida et al. (2016), Macrothelypteris is monophyletic and sister to the clade Phegopteris + Pseudophegopteris . These three genera form the subfamily Phegopteridoideae Salino, A.R. Sm. & T.E. Almeida.All are free-veined, often with forked veins, and the veins end before reaching the segment margins. They were clearly understood and delineated by Holttum (1969), who provided a revision/synopsis of these genera in the same paper. Holttum (1947, 1969, 1982) believed the phegopteroid genera in particular, but all of Thelypteridaceae , to be related to Cyatheaceae ( Holttum 1947, 1969, 1982). The Phegopteridoideae do indeed form the earliest diverging branch in Thelypteridaceae in molecular analyses, but all recent evidence suggests that they are not closely related to, or derived from, Cyatheaceae.

All necessary combinations in Macrothelypteris have been made by Ching (1963) and Holttum (1969, 1982). One African species,heretofore included in Macrothelypteris by Pichi Sermolli (1983), is here transferred to Pseudophegopteris .

Constituent species.— Macrothelypteris banaensis (Tardieu & C. Chr.) Christenh. ; * M. contingens Ching ; M. multiseta (Baker) Ching ; ** M. ogasawarensis (Nakai) Holttum ; * M. oligophlebia (Baker) Ching ; ** M. ornata (Wall. ex Bedd.) Ching ; * M. polypodioides (Hook.) Holttum ( Fig. 2G View FIG ); M. setigera (Blume) Ching ; * M. torresiana (Gaudich.) Ching ; ** M. viridifrons (Tagawa) Ching.