Polyphlebium Copel., Philipp. J. Sci.

Kessler, Michael & Smith, Alan R., 2017, Prodromus of a fern flora for Bolivia. X. Hymenophyllaceae, Phytotaxa 328 (3), pp. 201-226 : 217

Polyphlebium Copel., Philipp. J. Sci. 67: 55. 1938.

Polyphlebium , a pantropical genus of about 15 species, is widely distributed in the Neotropics, Polynesia, Australasia, Africa, and islands in the Indian Ocean ( Ebihara et al. 2006). The species are about evenly divided between Neotropics and Paleotropics. It has been recently redefined and expanded beyond the original single species and type, P. venosum (R.Br.) Copel. , which occurs in New Zealand and Australia. The species all have long-creeping, frequently branched, filiform rhizomes 0.1–0.8 mm diam., rhizomes densely covered with brownish hairs, relatively few, fine roots, well-spaced fronds, petioles mostly 1–5 cm long (sometimes green-alate), blades (1–)2–4-pinnate, lacking false veins, paratactic, tubular sori (involucres) with usually dilate lips, long-exserted receptacles, and x = 36. Habitally, Polyphlebium species resemble Hymenophyllum in having filiform rhizomes and being largely epiphytic. The species are usually on wet rocks or epiphytic on tree fern trunks. At least one species, P. borbonicum , appears to be amphioceanic ( Ebihara et al. 2009). The genus is sister to the much larger, combined clade of Crepidomanes + Vandenboschia + Didymoglossum ( Ebihara et al. 2006) .

Polyphlebium pyxidiferum was originally included within the circumscription of the genus by Ebihara et al. (2006), but this species is now placed in Crepidomanes ; we include it in the key below because of potential confusion with, and similarity to, species of Polyphlebium . Closest affinities of Polyphlebium are with the trichomanoid genera ( Trichomanes s.l.), generally, and preliminary trees suggest that it may be sister to a larger clade that includes Crepidomanes , Vandenboschia , and Didymoglossum , all pantropical groups.