Nephrolepis Schott, Gen. Fil.

Smith, Alan R. & Kessler, Michael, 2018, Prodromus of a fern flora for Bolivia. XXXVII. Nephrolepidaceae, Phytotaxa 334 (2), pp. 135-140 : 136

Nephrolepis Schott, Gen. Fil. : 1, pl. 3. 1834.

The genus and family are characterized by stoloniferous rhizomes, the stolons wiry and produced just behind the rhizome apices. The stolons are underground or sometimes aboveground, and protostelic, with subterranean ones producing globose tubers in some species. Blades are 1-pinnate broadly to narrowly lanceolate, with articulate, sessile pinnae and free, simple or forked veins; vein ends often end in cretaceous (with lime dots) hydathodes adaxially. Rachises often bear small scales. Blade apices narrow very gradually and mature slowly; pinnae are often inequilateral, with acroscopic base auricled. Sori are medial to inframarginal (marginal in a few extraterritorial species) and bear reniform or round-reniform indusia. x = 41, as in Dryopteridaceae , Oleandraceae , and some other eupolyploid I fern families.

Some species of Pecluma and Polypodium are superficially similar, but differ in their pinnatisect blades, lack of indusia, and lack of stolons. From Lomariopsis , in the closely related family Lomariopsidaceae , Nephrolepis differs in its monomorphic (vs. dimorphic) leaves, stoloniferous rhizomes, and usually much greater number of pinna pairs. From Cyclopeltis , another close relative, Nephrolepis differs by having a single row (vs. 1–3 rows) of sori on each side of the costae, reniform or round-reniform indusia (vs. peltate), non-conform, slowly maturing distal pinna, and wiry stolons.

Nephrolepis is monophyletic ( Hennequin et al. 2010, Zhang et al. 2016) and sister to the Lomariopsidaceae ( Hennequin et al. 2010) . Two main lineages in Nephrolepis were detected by Hennequin et al.: one Old World, the other neotropical, including four of the five native species in Bolivia, plus the cultivated and possibly naturalized N. cordifolia and N. exaltata . Only N. biserrata appears to have clear paleotropical affinities. A recent study by Yahaya et al. (2016), with broader sampling, provided support for this dichotomy; with data from several chloroplast genes, they also showed that the largest of the two clades comprised two subclades, one neotropical, the other largely paleotropical.

Nephrolepis is pantropical, with seven native and one paleotropical, widely naturalized species in the Americas; five of the neotropical species, all widespread, occur in Bolivia. The New World species were treated by Nauman (1981, 1985), and his concepts are basically still employed in most floras today. Recently, three new species were described from the Neotropics by Rojas (2008); one of these, N. obtusiloba , was ascribed a very broad range that included Bolivia (see comments under N. pendula ).

Nephrolepis brownii (Desv.) Hovenkamp & Miyam. (synonym: N. multiflora (Roxb.) Jarrett ex C.V.Morton ; see Hovenkamp & Miyamoto 2005), presumably native to tropical and subtropical Asia, Malesia, and Polynesia, and widely naturalized in Florida, West Indies, and southern Mexico to Brazil and Ecuador, may occur in Bolivia. It differs from all Bolivian species of Nephrolepis by the appressed, bicolorous (dark brown with narrow pale margins), 2–3 mm long scales on the petiole bases.

Nephrolepis is one of the most important horticultural fern genera ( Morton 1958, Hoshizaki & Moran 2001). Cultivars of N. cordifolia and N. exaltata , sometimes with highly dissected leaves, are commonly seen in Bolivian houses and may occasionally locally form naturalized populations, but there is currently little evidence that they are naturalizing outside cities; they are included in the key because they (and other species in the genus) are known to naturalize widely elsewhere (see, e.g., Hoshizaki & Moran 2001, Hovenkamp & Miyamoto 2005).