Grypothrix, (Holttum) S. E. Fawc. & A. R. Sm. (Holttum) S. E. Fawc. & A. R. Sm.

Fawcett, Susan & Smith, Alan R., 2021, A Generic Classification of the Thelypteridaceae, Fort Worth, Texas, USA: BRIT Press : 46-48

GRYPOTHRIX

Grypothrix (Holttum) S.E. Fawc. & A.R. Sm. , gen. et stat. nov.

— TYPE: Grypothrix cuspidata (Blume) S.E. Fawc. & A.R. Sm. [= Meniscium cuspidatum Blume, Enum.Pl.Javae 2:114.1828].— Pronephrium sect. Grypothrix Holttum

For complete synonymy, see Holttum (1982) and Lin et al.(2013).

Etymology.—Gr. grupon, hooked + thrix, hair, in reference to the hooked (hamate) hairs, which are diagnostic for the genus.

Plants terrestrial, small to medium-sized (10–)20–80(–120) cm tall, usually in forest understories or along streams at lower elevations; rhizomes short- to long-creeping; fronds monomorphic, weakly or strongly dimorphic (e.g., G. simplex , Fig. 3C ), pinnate, trifoliolate or simple, erect or arching; stipes stramineous, dull brown or reddish, scales linear-lanceolate, brown, castaneous or black, often with hamate hairs on surfaces and margins; blades chartaceous, sometimes drying reddish, with conform apex (or expanded apex with smaller lateral lobes), proximal pinnae not reduced, proliferous buds rarely present at pinna bases (e.g., G. cuspidata , G. ramosii ); pinnae margins usually entire, sometimes crenate, rarely shallowly lobed ( P. insularis ), bases cuneate, or sometimes cordate, sessile or short-petiolulate, pinnae generally broad (> 3cm), but quite narrow (<1 cm) in G. salicifolia ; veins usually prominent both adaxially and abaxially, reaching margins, several pairs regularly anastomosing to form a series of areoles, each with an included veinlet, or less commonly, a continuous excurrent vein; aerophores sometimes present in the form of a darkened swelling at pinna bases; indument abaxially of characteristic hyaline, hamate (hook-shaped) hairs, on costae and veins, present or absent between veins; indument adaxially of hamate hairs on costae and veins, present or absent between veins; pustules sometimes present on laminar tissue; sori exindusiate, elongate and coalescent along crossveins, sometimes very dense, appearing acrostichoid (e.g., G. simplex ), or, medial, round and discrete; sporangia glabrous or with hamate setulae or glands; spores brown or black, with fimbriate crests ( Patel et al. 2019a); x = 36, five species counted, with diploids, triploids, and tetraploids known. Holttum (1982) believed G. parishii to be a hybrid based on its variable morphology and suggested that G. triphylla was one parent. Triploid counts (n = 108) in G. simplex suggest it may be a hybrid ( Nakato 1987). See Notes for further discussion.

Diagnosis.—The most consistent character for distinguishing Grypothrix from other segregates of Pronephrium is the presence of hamate hairs somewhere on the body of the plant—scales, leaves, veins, or sporangia. Sometimes, however, these may be sparse, and difficult to observe (e.g., in G. sulawesiensis ). Sori of all species of Grypothrix are exindusiate, whereas indusia are sometimes present in species of Menisciopsis , Pronephrium s.s., and Abacopteris . The sori of most continental Asian species of Grypothrix are elongate and coalescent along cross-veins, which is less common among other Pronephrium segregates (but see Menisciopsis lakhimpurensis ); members of the Malesian clade of Grypothrix more frequently have round, discrete sori. Pronephrium s.s. is generally highly dimorphic ( Fig.7C ), and often bears spherical yellow glands on its sporangia or elsewhere, whereas most species of Grypothrix are monomorphic or weakly dimorphic (with the exception of G. simplex , which differs from nearly all Pronephrium s.s. in having simple blades, Fig. 3C ) and do not bear such glands.

Biogeography and ecology.— The 12 species of Grypothrix are Malesian, Melanesian, Australasian, and southeast Asian in distribution, with species extending into India, Sri Lanka, Myanmar, Thailand, Vietnam, China, Japan, and Korea. Grypothrix triphylla is especially widespread, extending from subtropical east Asia, throughout Malesia, and into northern Queensland and Fiji ( Holttum 1977b, 1982). A few species are restricted to continental Asia, and others are endemic to Taiwan ( G. longipetiolata ) or to Taiwan and Japan ( P. insularis ) ( Iwatsuki 1959; Lin et al. 2013).

Taxonomic and phylogenetic studies.— Holttum (1982) treated Grypothrix as a section of Pronephrium ; all species in this section (here elevated to genus) have hamate hairs on the scales, laminae, veins, and/or sporangia. No earlier workers had recognized the taxonomic utility of these unusual hairs. This is the only Holttum segregate of Pronephrium (or any of his infrageneric taxa) that we elevate in rank with identical circumscription. It can be distinguished from closely related genera on the basis of a single synapomorphy—the presence of hamate (hooked) hairs somewhere on the plant. Similar hairs also occur in distantly related taxa within Thelypteridaceae , e.g., in sect. Uncinella of the mostly neotropical genus Amauropelta ( Smith 1974) , and in Cyclogramma .

Grypothrix comprises two monophyletic subclades with different distributions: the species of one subclade are predominantly continental Asian, and the species of the other are Malesian. Grypothrix is a member of the chingioid clade which includes the monophyletic genera Chingia , Menisciopsis (also segregated from Pronephrium s.l.), Mesopteris , and Plesioneuron . Grypothrix and Menisciopsis , like the closely related Mesopteris , share a tendency to turn red when dry, as suggested by some of their specific epithets: Grypothrix rubicunda , Menisciopsis rubida , and M. rubrinervis .

Notes.— A hybrid between G. triphylla and G. cuspidata has been reported from Taiwan ( Knapp 2011). Pronephrium thwaitesii , an unusual taxon from India and Sri Lanka treated in Pronephrium sect. Grypothrix by Holttum (1972), had not been collected for more than a century, and had been presumed extinct. Holttum suggested it might be a hybrid involving G.triphylla ( Holttum 1972) .The plant was relocated by Nayar and Geeverghese (1987), who conducted a careful examination of its morphology, including spore development, and agreed that it was a hybrid involving G. triphylla ; they then suggested Christella parasitica is the second parent. A hybrid described from Taiwan, recently treated as Pronephrium insulare, is also triploid (n = 108), and postulated to represent a cross between Christella dentata and Pronephrium triphyllum (considered by us to belong to Grypothrix ); it was given a name as a nothogenus, × Chrinephrium insulare ( K. Iwats.) Nakaike ( Kuo et al. 2019). As noted by Iwatsuki (1959), in his taxonomic concept, Abacopteris (which included several species of Grypothrix ) is distinguished from Cyclosorus (including Christella s.s.) by lacking sinus membranes, although these are present in this purported hybrid. As putative examples of intergeneric hybridization, these hypotheses warrant further investigation.

Incertae sedis.— Pronephrium insulare ( K. Iwats.) Holttum (= × Chrinephrium insulare ( K. Iwats.) Nakaike) and Pronephrium thwaitesii may represent triploid species of Grypothrix or, potentially, hybrids between Christella and Grypothrix triphyllum , but pending further study, we refrain from making new combinations.

Figures

FIG. 3.Grypothrix cuspidata,Lu 12803 (VT),A.habit.B. pinna,abaxial view.C. G.simplex, Lu 9270 (VT),habit.

FIG.7.A.Pneumatopteris parksii,Fawcett 645 (UC),pinna lobes,adaxial view.B.Reholttumia magnifica,Fawcett 676 (VT),pinna lobes,abaxial view.C.Pelazoneuron patens,Fawcett 744 (VT), abaxial pinna-lobes.D. P.serra,Fawcett 1034 (VT), adaxial pinna lobes.E. Pakau pennigera, Given 11842 (VT),pinna lobes,abaxial view. F.Pakau pennigera, Stuart s.n.(VT),pinna.