Nephrolepis biserrata (Sw.) Schott, Gen. Fil.

Smith, Alan R. & Kessler, Michael, 2018, Prodromus of a fern flora for Bolivia. XXXVII. Nephrolepidaceae, Phytotaxa 334 (2), pp. 135-140 : 137

Nephrolepis biserrata (Sw.) Schott, Gen. Fil. t. 3. 1834.

Range: —Florida; Antilles; southern Mexico to Bolivia (BE, CO, LP, PA, SC) and Brazil; Africa; Asia; Polynesia.

Ecology: —Fairly common; epiphytic, terrestrial, and saxicolous, often along roadsides, in secondary growth, and along forests borders, sometimes growing in leaf axils of palms, in humid regions; to 500 m.

Notes: —A variable and pantropical species, with more than 25 heterotypic synonyms listed by Hovenkamp & Miyamoto (2005). Rhizomes and petiole bases with spreading, concolorous scales 5–7 mm long; blades (11) 16–30 cm wide, to 3 m long, abaxially with hairs 0.2–0.6 mm long; costae adaxially with dense, catenate hairs 0.1–0.5 mm long; indusia round-reniform with occasional hairs. The species may be a complex, even in Bolivia, with typical N. biserrata having mostly (entirely) segmented hairs abaxially, and another variant with few hairs but sparse to moderately dense scales. However, a sampling of specimens from five localities ( Bolivia, Comores, Sudan, and Indonesia) by Hennequin et al. (2010) showed the species to be monophyletic. The type of N. biserrata is from Mauritius.

A recent collection from Dept. La Paz, Gonzales 4875 (UC), deviates from the pantropical N. biserrata and all other specimens from Bolivia in several seemingly significant characters: blade scales lacking on the costae and rachises, and long-septate hairs present on both sides of the costae, and between veins abaxially. The much more common and typical form of this species in Bolivia and elsewhere has scales along the costae abaxially, often lacks hairs between veins abaxially, and lacks or has sparse hairs on the costae adaxially. These two forms may be specifically different, but in the absence of more detailed morphological and molecular studies in Nephrolepis , which must be broadly based (a range of specimens from throughout the Americas and beyond), we refrain from giving this a name. The type of N. mollis Rosenst. , from Costa Rica (Brade & Brade 141, isotype UC!), appears to match the hairy, scaleless variant of this species, as does Sieber, Syn. Fil. 35, UC, from Mauritius.

In an analysis by Yahaya et al. (2016), using both chloroplast and nuclear markers, N. biserrata was not monophyletic, but some populations of this species from Malaysia, Malesia, and Africa show a sister relationship to a complex of clades comprising elements identified as N. brownii , N. exaltata , other populations of N. biserrata , and several other Old World species.