Pseudophegopteris, Ching, Ching

Fawcett, Susan & Smith, Alan R., 2021, A Generic Classification of the Thelypteridaceae, Fort Worth, Texas, USA: BRIT Press : 75-76

PSEUDOPHEGOPTERIS

Pseudophegopteris Ching , Acta Phytotax. Sin. 8:313. 1963.

— TYPE: Pseudophegopteris pyrrhorhachis (Kunze) Ching [= Polypodium pyrrhorhachis Kunze ]

Toppingia O. Deg., I. Deg. & A. R.Sm. ex O. Deg.& I. Deg.

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

Etymology. —Gr. pseudo, false + phegos, beech + pteris = fern; a distinctive relative of Phegopteris .

Plants terrestrial, fronds of determinate growth (except in P. keraudreniana , where growth is indeterminate), mostly medium-sized to very large, 50–300+ cm tall; rhizomes short- to long-creeping, or ascending, or erect, with thin scales, these brown to tan, lanceolate, with scattered hairs along margins and sometimes sparingly on surface; fronds clustered, or remote, monomorphic; stipes 30–60 cm long, not grooved adaxially, stramineous to red-brown, often glossy; stipe scales thin, lanceolate to ovate, light brown, 2–6 mm long, typically with superficial hairs; blades herbaceous to chartaceous, lacking buds or proliferations, pinnate-pinnatifid to bipinnate-pinnatifid or slightly more divided, with blade apex gradually tapering and pinnatifid; proximal pinnae of well-developed fronds not reduced or with 1–2 lowermost pairs somewhat reduced (sometimes to less than half the length of longest pinnae), but blades lacking greatly reduced, glanduliform pinnae; rachises adaxially not grooved, bearing simple and sometimes forked acicular hairs, some spp. glabrescent, typically lacking scales at maturity (except P. dianae , which is densely and persistently scaly); pinnae usually opposite to subopposite, sessile or increasingly adnate, especially more distal pinna (e.g., as in P.rectangularis ), spreading or obliquely spreading, costae not grooved adaxially, truncate at bases, acute at tips, to ca. 15(–20) × 2(–3) cm wide, pinnatifid or pinnate-pinnatifid with pinnules strongly adnate and often connected at their bases, in larger species free, sessile or nearly so, with or without acroscopic and/or basiscopic, more lobed basal auricles; veins free, often forking in ultimate segments, ± prominent, at least readily visible on both sides, vein ends clavate adaxially and not reaching segment margins; aerophores absent at pinna bases; indument abaxially, if present, of sparse to moderately dense unicellular hyaline acicular hairs, lacking scales, blades often glabrescent with age; short-stipitate glands sometimes present along costae and costules; indument adaxially of hyaline acicular hairs to ca. 1 mm long along costae, sometimes also with hairs on costules and ultimate veins, occasionally on laminar tissue between veins; pustules absent on abaxial surfaces between veins; sori medial to supramedial, round to oblong (length 2 × width), exindusiate, not confluent at maturity; sporangia short-stalked, capsules glabrous or with short setulae 0.1–0.2 mm and/or yellowish short-stipitate glands ca. 0.1 mm adjacent to annulus; spores tan to brown, with numerous shallow and narrow ridges forming a reticulate network of polygonal areoles having a smooth or papillate surface ( Holttum 1969; Tryon & Lugardon 1991; Patel et al. 2019a), lacking broad wings; x = 31, diploids and tetraploids known, about 10 spp. counted. No hybridization with any other genus has been demonstrated.

Diagnosis. —Characters used by Holttum (1969) to separate Pseudophegopteris from Macrothelypteris include: 1) thinner, brownish stipe base and rhizome apex scales on Pseudophegopteris (vs. pale thickened scales); 2) absence of septate hairs on axes and blades in Pseudophegopteris (vs. often septate); and exindusiate sori (vs. often with small indusia). In addition, ultimate segments and distal pinnae in Pseudophegopteris are more pronouncedly adnate, the pinnae are opposite (vs. alternate), and there are differences in spore ornamentation. These two genera have retained their rank in publications on the family by Smith (1990, 2006) and in PPG I (2016), as well as many recent floras.

Biogeography and ecology.— Pseudophegopteris comprises 28 species and is widely distributed from tropical West Africa (and offshore island endemic species on São Tomé and St. Helena), Madagascar, Réunion, India, southeast Asia, and Japan, through Malesia to Fiji and Hawaii ( Holttum 1969). The greatest diversity in the genus is in China, with 12 species (including four endemics), one with two varieties ( Lin et al. 2013). One of the oceanic island endemics, P.dianae , from St. Helena, is remarkable in its very dense, persistent, light brown, glabrous, ovate scales along the rachis. The other five Atlantic and Indian Ocean island species, P.andringitrensis , P. aubertii , P.cruciata , P. henriquesii , and P.rammelooi (see Holttum 1977b; Pichi Sermolli 1983), are much more similar to the larger, bipinnate-pinnatifid species such as P. yunkweiensis and P.paludosa , from southeast Asia and Malesia ( Holttum 1974a). The sole species in Hawaii, P.keraudreniana , is quite rare and localized; it differs from all others in the genus in having indeterminate growth, with dormant tips growing intermittently after lower pinnae mature ( Palmer 2003). Species of Pseudophegopteris occur mainly along streams, in thickets, and in rock crevices in dense lowland and montane forests, up to 3100 m; most species occur from 1000–2500 m.

Taxonomic and phylogenetic studies.— Both Pseudophegopteris and Macrothelypteris were first recognized at generic rank by Ching (1963). Holttum’s studies further clarified their distinction and differences ( Holttum 1969, 1971, 1974a, 1977b, 1982). Pseudophegopteris is most closely related to Macrothelypteris and Phegopteris , which together constitute the subfamily Phegopteridoideae ( PPG I 2016) . 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), Pseudophegopteris is monophyletic and sister to a monophyletic Phegopteris , and this combined clade is in turn sister to Macrothelypteris . The close relationship of these three genera is evidenced by the fact they are all free-veined, often with forked veins that end before reaching the segment margins, and stipes, rachises, and costae not grooved adaxially. This separates them from all other genera of Thelypteridaceae , except Metathelypteris and some Leptogramma , which are not closely related. The phegopteroids were clearly understood and delineated by Holttum (1969), who provided a revision/synopsis of these genera, prior to their recognition as subfamily Phegopteridoideae( PPG I2016) .In part,because of the greater blade dissection in Pseudophegopteris and Macrothelypteris , but also because of a belief in the relationship of Thelypteridaceae to Cyatheaceae ( Holttum 1947, 1969, 1982), Holttum thought these three genera showed the most primitive frond-form in the family. Although they are sister to all other taxa of Thelypteridaceae in molecular analyses, all evidence suggests that they are not closely related to, or derived from, Cyatheaceae.

Notes. —Based on a sample of five species, spores of Pseudophegopteris are very distinctive and consistently sculptured: low ridges forming a polygonal reticulate network, smooth papillose intra-areolar surfaces, and a gemmulate exospore ( Tryon & Lugardon 1991). This is somewhat similar to Phegopteris , which has spores that differ in having a relatively unsculptured surface or a more coarsely reticulate network with a tuberculate intra-areolar surface. Spores of Macrothelypteris have a finer reticulate network of ridges with smaller, more rounded areoles (similar to spores of some species of Amauropelta ), or a coarser, more irregular network of perforate folds ( Tryon & Lugardon 1991).

All necessary combinations except one have been made in Pseudophegopteris , by Holttum (1969, 1982).