Coryphopteris

Fawcett, Susan & Smith, Alan R., 2021, A Generic Classification of the Thelypteridaceae, Fort Worth, Texas, USA: BRIT Press : 37-38

CORYPHOPTERIS

Coryphopteris Holttum, Blumea 19:33. 1971.

— TYPE: Coryphopteris viscosa (Baker) Holttum [= Nephrodium viscosum Baker ].

Wagneriopteris Á.LÖve & D. LÖve

For additional synonymy, see Holttum (1976a, 1977b, 1982), Lin et al.(2013).

Etymology.— Gr. korupho, latinized Coryph, summit, crest + pteris, fern, in reference to the propensity of species of this genus to grow on ridgetops in the Paleotropics.

Plants terrestrial (rarely epiphytic), of temperate forest understories, or tropical montane habitats, small to medium-sized (10 cm to 1 m tall); rhizomes erect and trunk-like (rarely creeping, e.g., in the temperate species C. simulata ); fronds monomorphic to weakly dimorphic (fertile fronds slightly taller and with slightly narrower pinnae), pinnate-pinnatifid to pinnate-pinnatisect, rarely fully bipinnate (e.g., C. habbemensis ); stipes stramineous, castaneous, or dull brown; stipe scales linear-lanceolate to ovate, thin to stiff, usually glabrous, these often transitioning to filiform scales, or uniseriate hairs on abaxial laminar axes ( Fig. 2L ); blades membranaceous to chartaceous, drying green or blackish, apex gradually reduced, proximal pinnae typically largest, not or only slightly reduced, often deflexed, rarely with a few to many pairs of proximal pinnae gradually reduced (e.g., C. nipponica , C. fasciculata ); proliferous buds absent; pinna margins entire or slightly dentate, segments often parallel-sided and little tapered, with apices rounded, truncate, less often acute, often nearly perpendicular to costae (never strongly oblique), bases with one or more proximal pinna lobes sometimes free or sometimes with lobed acroscopic auricles; veins always free, mostly simple (rarely forking), reaching margins, costae grooved adaxially; aerophores absent or present as minor swellings; indument abaxially of hyaline acicular hairs, almost always also with glands, which may be stipitate or sessile, viscid or resinous, reddish, amber, or golden, never sulfur-colored (glands sometimes difficult to observe on dried specimens); scales often present abaxially along stipes and costae, transitioning to multicellular hairs; indument adaxially of unicellular or septate hyaline acicular hairs restricted to axes, or also present on laminar tissue between veins, sessile or stipitate glands sometimes present; pustules absent; sori usually round, sometimes slightly elongate on distal portion of segments, discrete, medial to costular, indusia typically present, these glabrous, or with acicular hairs or glands ( Fig. 2A ); sporangia short-stalked, capsule lacking hairs or glands, stalk sometimes with gland; spores typically pale, with perforate perine ( Patel et al. 2019a), and often with fimbriate wings; x = 31, 32, 33 seven species counted, diploids, triploids and tetraploids known, although additional counts are needed to verify the base numbers. Infrageneric hybrids between C. japonica and C. musashiensis are well documented ( Nakato et al. 2004).

Diagnosis.— Coryphopteris is most similar to Amauropelta s.l., but it may be distinguished by its usually erect, trunk-like rhizomes, proximal pinnae largest or only slightly reduced, and by the presence of filiform scales or multicellular hairs along abaxial costae. Metathelypteris differs from both genera in having adaxial costae lacking a groove, and veins ending before the margins. The presence of abundant septate hairs on the adaxial axes of the laminae, frequent in Coryphopteris , is an unusual feature within the Thelypteridaceae ( Holttum 1976a) .

Biogeography and ecology.— Coryphopteris is widely distributed on mainland Asia from northeastern India to southern Russia. It is most diverse in the mountainous areas of Malesia, Melanesia, and Polynesia, usually above 1000 m. There is also a single species endemic to North America, and this has a primary distribution to the east from southern Canada to Virginia, and disjunct populations in the Great Lakes region ( Smith 1993a). The genus includes 68 species and reaches its greatest diversity in the mountains of Papua New Guinea. Throughout their range, Coryphopteris species often occur in acidic or low-nutrient soils. In temperate North America, habitats include forest understories, often in mixed hardwood-conifer swamps, or wetland margins, frequently in association with Sphagnum. Holttum (1982) described tropical species as distributed exclusively on high elevation ridgetops, where the soils were leached, nutrient poor, and highly acidic, a habitat not normally shared with other members of Thelypteridaceae .

Taxonomic and phylogenetic studies. —The genus was first described by Holttum (1971) and monographed soon after ( Holttum 1976a). Holttum’s work dealt largely with the Malesian and Pacific species, and he described 50 of the 68 currently recognized species as new to science. Only three additional species belonging to this genus ( Kato 2007; Lorence et al.2011; Ebihara et al. 2020) have been described since Holttum (1982).Most Chinese species of Coryphopteris recognized here were treated by Ching (1963) in Parathelypteris . Holttum’s (1976a) concept of Coryphopteris largely followed that of Ching for Chinese species in the group, recognizing only two species of Coryphopteris in mainland Asia: C. hirsutipes and C. petelotii . Despite rhizome differences—typically erect caudices in Coryphopteris , creeping rhizomes in Parathelypteris (= Amauropelta subg. Parathelypteris in our treatment)—Holttum noted the striking similarities (notably spores and sporangia) between some species of Parathelypteris s.l. and Coryphopteris , and expressed uncertainty about the taxonomic boundaries between the two genera in China and Japan ( Holttum 1976a).

Holttum (1976a) considered Coryphopteris angulariloba , and C. indochinensis to be among seven heterotypic synonyms of a broadly variable C. hirsutipes , but he did not have access to type material for all of his synonyms. We follow Lin et al. (2013) and He & Zhang (2012) in recognizing these taxa as distinct. Pending further study, which may refine species delimitation, all necessary combinations in Coryphopteris are provided below.

Critical insights into the relationships among temperate and subtropical Asian Parathelypteris s.l. were provided by molecular phylogenetic studies ( Ebihara et al. 2011; He & Zhang 2012); these resolved Parathelypteris in two distinct clades—one, including the type, resolving with Amauropelta s.s. (subg. Amauropelta ), and the other, with Coryphopteris , which is sister to a clade that includes Amauropelta s.s., Parathelypteris , and Metathelypteris . The sole North American species, Coryphopteris simulata (type of Wagneriopteris), was shown to be closely related to a Japanese accession of the East Asian species Coryphopteris nipponica ( Fawcett 2018) , both of which had been treated previously in Parathelypteris . Based on their molecular evidence, He and Zhang (2012) published new combinations in Coryphopteris for some species of Parathelypteris . We provide new combinations for an additional 11 species below, based on additional sampling (Fawcett et al. in press) and morphological study. In the present classification, the species of Parathelypteris (which has been shown to be polyphyletic) are treated in Coryphopteris in Coryphopteris or in three of the four subgenera of Amauopelta: subg. Parathelypteris , subg. Nibaa, and subg. Venus.

Based on certain morphological similarities to Cyathea (e.g., erect caudices, septate acicular hairs on adaxial axes, short-stalked sporangia), Holttum (1971, 1976a) hypothesized that Coryphopteris was “primitive” in the family and derived from a tree-fern lineage. All large-scale molecular studies of fern relationships (e.g., Testo & Sundue 2016) suggest that these groups are in fact quite distantly related.

Notes. —The name Parathelypteris nipponica has been broadly applied to plants from Japan, Korea, and China. The type is from Japan, and has been resolved in the Coryphopteris clade ( Ebihara et al. 2011), while plants from China determined as such have been resolved near to Parathelypteris s.s. ( He & Zhang 2012).Although they are strikingly similar— both have creeping rhizomes, sessile yellow glands on abaxial laminae, and several pairs of reduced proximal pinnae—typical Coryphopteris nipponica usually has three or fewer pairs of reduced proximal pinnae, while the Chinese plants, historically recognized as this, tend to have more than three pairs of gradually reduced proximal pinnae, and are most closely allied to Amauropelta beddomei (Fawcett et al. in press). This complex group of plants is in need of critical study and taxonomic revision ( Ebihara & Nitta 2019). In tropical regions, as Holttum (1976a) noted, many of the localities that support Coryphopteris are difficult to access and have likely never been visited by botanical collectors. He further stated that anyone wishing “to make a general study of them would need to be very energetic and also have considerable resources for travel at his disposal” ( Holttum 1976a:21).

Figures

FIG. 2. Morphology of the Thelypteridaceae.A. Coryphopteris kolombangarae, SITW07554 (TAIF), glandular indusia.B. Goniopteris yaucoensis, Proctor 43584 (US), stellatehairs along adaxialcosta.C.Pneumatopterisglandulifera,SITW11069 (TAIF),peg-like aerophoresat pinna bases.D.Sphaerostephanospolycarpos,SITW11070 (TAIF),marginally glandular indusia.E.Sphaerostephanos doodioides,SITW05702(TAIF),setoseindusia,spherical glands on indusia,sporangia,and laminar tissue. F. Goniopteris reptans, Wright 813 (US), sori with shriveled, setose indusia, some hairs furcate. G. Macrothelypteris polypodioides, SITW11122 (TAIF), stipe scales. H. Hoiokula pendens, Hobdy 2664 (UC), setulose sporangia. I. Plesioneuron imbricatum, SITW05370 (TAIF), exindusiate sori, sporangia with spherical glands. J. Christella dentata, SITW10525 (TAIF), shriveled,setulose indusia.K. Sphaerostephanos heterocarpos SITW11079 (TAIF),abruptly reduced proximal pinnae,adaxial surface with acicular hairs.L. Coryphopteris subbipinnata, SITW11667 (TAIF),appressed stipe base scales,these marginally setulose.All photos by Cheng-Wei Chen except B,F,and H by Susan Fawcett.