Classification
 Nomenclature
Scientific Name:
Hypolepis Bernh., Neues J. Bot. 1(2): 34 (1805)
Type Taxon:
Hypolepis tenuifolia (G.Forst.) Bernh. ex C.Presl
Etymology:
From the Greek hypo- (under) and lepis (a scale), a reference to the protection of the sori beneath a reflexed portion of the margin.
 Description

Terrestrial ferns. Rhizomes long-creeping, bearing red-brown or pale brown multicellular hairs. Fronds monomorphic. Stipes hairy or occasionally spiny (not NZ). Laminae 2–5-pinnate, herbaceous or coriaceous, bearing glandular and/or non-glandular hairs; primary pinnae stalked, lacking basal pinnule-like stipules. Veins free. Sori round or elliptic, superficial, submarginal; paraphyses present or absent. Indusia either absent, or formed from reflexed lamina flaps that vary from membranous and sharply reflexed to green and partially reflexed, opening inwards; inner indusium absent. Spores monolete, usually echinate and more or less reticulate, rarely almost smooth.

 Taxonomy

Most species of Hypolepis form a clearly defined genus distinct from the other genera in Dennstaedtiaceae on morphological (Brownsey 1998) and molecular grounds (Schuettpelz & Pryer 2007; Perrie et al. 2015). The genus has been revised in Australia (Brownsey & Chinnock 1984; Brownsey 1998), New Zealand (Brownsey & Chinnock 1984) and Malesia and the Pacific (Brownsey 1987), whilst the H. rugosula complex has been analysed worldwide by Schwartsburd & Prado (2014). The latter authors recognised 15 distinct geographic subspecies within H. rugosula, including the taxa that we recognise here as H. amaurorhachis, H. lactea and H. rufobarbata. In our opinion there is ample morphological evidence for recognising these three taxa as species in New Zealand, as well as a ploidy difference between them and H. rugosula in Australia.   

Whether the morphological and cytological distinctiveness of H. distans and perhaps some other related species (Brownsey 1983) merits the recognition of a separate genus requires further investigation.

 Key
1Veins of ultimate lamina segments ending in a small marginal sinus; basal pair of primary pinnae arising at c. 90° to rachisdistans
Veins of ultimate lamina segments never ending in a marginal sinus; basal pair of primary pinnae arising at 20–80° to rachis2
2Sori protected by well-developed, reflexed, partially membranous, lamina flaps; stipes 2–15 mm diameterdicksonioides
Sori unprotected, or protected only by slightly reflexed, green, lamina flaps; stipes 1–6 mm diameter3
3Abaxial surface of lamina and rachis bearing only non-glandular hairs4
Abaxial surface of lamina and rachis bearing at least some glandular hairs as well as acicular hairs5
4Laminae up to 770 mm long and 400 mm wide; ultimate lamina segments less than 1 mm wide; paraphyses absent from sorimillefolium
Laminae up to 1200 mm long and 1200 mm wide; ultimate lamina segments more than 1 mm wide; paraphyses sometimes present in soriambigua
5Lamina margins bearing abundant red-brown (or occasionally colourless) acicular hairs; stipe and rachis purple-brownrufobarbata
Lamina margins bearing colourless glandular or acicular hairs; stipe and rachis pale brown, red-brown or purple-brown6
6Glandular hairs on laminae 0.1–0.3 mm long; stipe and rachis red-brown or purple-brown for at least ¾ their length; plants largely confined to North Island and northern South Islandlactea
Glandular hairs on laminae 0.3–1.0 mm long; stipe and rachis red-brown for c. ½ their length; plants of southern South Island and subantarctic islandsamaurorhachis
 Recognition

In New Zealand, species of Hypolepis can be recognised by their creeping rhizomes, highly divided laminae bearing glandular or non-glandular hairs, and more or less round submarginal sori that are either unprotected, or protected by reflexed lamina flaps that open inwards.

 Distribution

A genus of 40–50 species in tropical and temperate regions of Central and South America, southern Africa, India, China, Japan, south-east Asia, Australasia and the Pacific (Brownsey 1998; Yan et al. 2013). There are about 15 species in the Americas (Tryon & Tryon 1982), but the greatest diversity is in the Old World, with three species in Africa (Roux 2009), eight in China (Yan et al. 2013), 14 in Malesia and the Pacific (Brownsey 1987), and seven in Australia (Brownsey & Chinnock 1987). Seven species in New Zealand; four endemic.

 Biostatus
Indigenous (Non-endemic)
Number of species in New Zealand within Hypolepis Bernh.
CategoryNumber
Indigenous (Endemic)4
Indigenous (Non-endemic)3
Total7
 Cytology

The base chromosome number in Hypolepis is either x = 26 or x = 52. However, there are also reports of n = 28, 29, 39 and 98, suggesting polyphyly, or aneuploidy within the genus (Brownsey 1983).

 Bibliography
Bernhardi, J.J. 1805: Dritter Versuch einer Anordnung der Farrnkräuter. Neues Journal für die Botanik 1(2): 1–50.
Brownsey, P.J. 1983: Polyploidy and aneuploidy in Hypolepis, and the evolution of the Dennstaedtiales. American Fern Journal 73: 97–108.
Brownsey, P.J. 1987: A review of the fern genus Hypolepis (Dennstaedtiaceae) in the Malesian and Pacific regions. Blumea 32: 227–276.
Brownsey, P.J. 1998: Dennstaedtiaceae. In: Flora of Australia. Vol. 48. 214–228.
Brownsey, P.J.; Chinnock, R.J. 1984: A taxonomic revision of the New Zealand species of Hypolepis. New Zealand Journal of Botany 22(1): 43–80.
Brownsey, P.J.; Chinnock, R.J. 1987: A taxonomic revision of the Australian species of Hypolepis. Journal of the Adelaide Botanic Gardens 10: 1–30.
Brownsey, P.J.; Perrie, L.R. 2018: Dennstaedtiaceae. In: Breitwieser, I.; Wilton, A.D. (ed.) Flora of New Zealand — Ferns and Lycophytes. Fascicle 19. Manaaki Whenua Press, Lincoln.
Kramer, K.U.; Green, P.S. 1990: Pteridophytes and gymnosperms. Kubitzki, K. (ed.) The Families and Genera of Vascular Plants. Vol. 1. Springer-Verlag, Berlin.
Perrie, L.R.; Shepherd, L.D.; Brownsey, P.J. 2015: An expanded phylogeny of the Dennstaedtiaceae ferns: Oenotrichia falls within a non-monophyletic Dennstaedtia, and Saccoloma is polyphyletic. Australian Systematic Botany 28: 256–264.
Roux, J.P. 2009: Synopsis of the Lycopodiophyta and Pteridophyta of Africa, Madagascar and neighbouring islands. Strelitzia 23: 1–296.
Schuettpelz, E.; Pryer, K.M. 2007: Fern phylogeny inferred from 400 leptosporangiate species and three plastid genes. Taxon 56: 1037–1050.
Schwartsburd, P.B.; Prado, J. 2014: Subspecies of Hypolepis rugosula (Dennstaedtiaceae; Pteridophyta) around the world: morphological and biogeographic perspectives. Acta Botanica Brasilica 28: 206–226.
Tryon, R.M.; Tryon, A.F. 1982: Ferns and allied plants. Springer-Verlag, New York.
Yan, Y.; Qi, X.; Liao, W.; Xing, F.; Ding, M.; Wang, F.; Zhang, X.; Wu, Z.; Serizawa, S.; Prado, J.; Funston, A.M.; Gilbert, M.G.; Nooteboom, H.P. 2013: Dennstaedtiaceae. In: Zhengyi, W.; Raven, P.H.; Deyuan, H. (ed.) Flora of China. Lycopodiaceae through Polypodiaceae. Vol. 2–3. Science Press, Beijing.