Polystichum

Polystichum is a genus of ferns in the family Dryopteridaceae, subfamily Dryopteridoideae, according to the Pteridophyte Phylogeny Group classification of 2016 (PPG I). The genus has about 500 species and has a cosmopolitan distribution. The highest diversity is in eastern Asia, with about 208 species in China alone; the region from Mexico to Brazil has at least 100 additional species; Africa (at least 17 species), North America (at least 18 species), and Europe (at least 5 species) have much lower diversity. Polystichum species are terrestrial or rock-dwelling ferns of warm-temperate and montane-tropical regions (a few species grow in alpine regions). They are often found in disturbed habitats such as road cuts, talus slopes, and stream banks.

Polystichum
Polystichum setiferum
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Division:	Polypodiophyta
Class:	Polypodiopsida
Order:	Polypodiales
Suborder:	Polypodiineae
Family:	Dryopteridaceae
Subfamily:	Dryopteridoideae
Genus:	Polystichum Roth
Species
See text.
Synonyms
Acropelta T.Nakai Adenoderris J.Sm. Aetopteron Ehrh. ex House Hemesteum H.Lév. Hypopeltis Michx. Papuapteris C. Chr. Phanerophlebia C. Presl Plecosorus Fée Sorolepidium Christ

Description

Many ferns of this genus have stout, slowly creeping rootstocks that form a crown, with a vase-like ring of evergreen fronds 30 to 200 centimetres (10 to 80 in) long. The sori are round, with a circular indusium, except in South American species which lack an indusium. The stipes have prominent scales and often have hair-like cilia, but they lack any true hairs. The genus differs from the well-known and allied fern genus Dryopteris in the indusium being circular, not reniform, and in having the leaf segments with auricles—asymmetrical blades where one side of the segment is much longer than the other at the base.

Apomixis

Apomixis, the development of an embryo without the occurrence of fertilization, is particularly common among ferns. Apomixis evolved several times independently in three different clades of polystichoid ferns.

Taxonomy

Polystichum is one of the 10 largest fern genera and is grouped within the Dryopteridaceae.Polystichum s.l. is well defined as its own monophyletic group, including species from the genera Cyrtomidictyum, Cyrtogonellum, Cyrtomium, and Phanerophlebia. Research concerning taxonomy within Polystichum s.s. is ongoing, with high levels of hybridization, allopolyploidy, and apomixis making distinctions difficult. Based on genetic analysis Little & Barrington (2003) originally defined a monophyletic Polystichum s.s. by removing Cyrtomium as its own genus. It was further separated by Li et al. (2008) into a separate clade along with Phanerophlebia.

Selected species

The genus has a large number of species. The PPG I classification suggested that there were about 500 species; as of February 2020^[update], the Checklist of Ferns and Lycophytes of the World listed 397 species and 58 hybrids, noting that "many undescribed species remain". The genus Polystichum includes, but is not limited to, the following species. In this list, a species name preceded by (=) is considered to be a synonym of the accepted species name above it.

• (Franch.) H. Christ
• Polystichum acrostichoides (Michx.) Schott – Christmas fern
• Polystichum aculeatum (L.) Roth ex Mert. – Hard shield fern
• H.Christ
• Ching & K.H.Shing
  (=) Polystichum wuyishanense Ching & K.H.Shing
• (Baker) Diels
• Polystichum aleuticum C.Chr. – Aleutian shield fern
• Hopkins – Anderson's hollyfern
• Bedd.
• Polystichum australiense Tindale
• (Atk. ex C.B.Clarke) Diels
• (Blume) T.Moore
• Ching & S.K.Wu
• Polystichum bonapartii Rosenst.
• W.H.Wagner & Hobdy – Bonsey's Hollyfern
• (J.F.Gmel.) C.Chr. – Rusty swordfern
• Polystichum braunii (Spenner) Fée – Braun's shield fern, Braun's hollyfern
• (Kunze) Ching
  (=) Polystichum garhwalicum N.C.Nair & Nag
• Polystichum bulbiferum Barrington
• Polystichum calderonense Proctor – Monte Guilarte hollyfern
• Polystichum californicum Diels – California sword fern
• (Baker) Diels
  (=) Polystichum michelii H.Christ
  (=) Polystichum minusculum H.Christ
  (=) Polystichum molliculum H.Christ
• (C.B.Clarke) B.K.Nayar & S.Kaur
• (H.Chr.) Diels
• Ching
• Ching
• (Maxim.) Diels
• C.Chr.
• (Hook.) J.B.Armstr. – Alpine shield fern
• (Baker) Diels
• H.Christ
• (D.Don) J.Sm.
• Polystichum drepanum (Sw.) C.Presl
• Polystichum dudleyi Maxon – Dudley's sword fern
• (C.Hope) C.Chr.
  (=) Polystichum tsuchuense Ching
• (J.F.Gmel.) C.Chr. – Rusty swordfern
• Ching
• Ching
• (Mett. ex Kuhn) C.Chr.
  (=) Polystichum tialooshanense Ching
• Hayata
• C.Presl
• Polystichum fallax Tindale
• Rosenst.
• C.Presl
• Ching & S.K.Wu
  (=) Polystichum rarum Ching & S.K.Wu
• C.Chr.
  (=) Polystichum kiusiuense Tagawa
• Ching ex W.M.Chu & Z.R.He 2001
• Brack. – Island swordfern
• (Hance) Diels
• Diels
• Ching & Z.Y.Liu
• Polystichum imbricans (D.C. Eaton) D.H.Wagner – Narrowleaf sword fern
• J.P. Roux
• Polystichum kruckebergii W.H.Wagner – Kruckeberg's sword fern/holly fern
• D.H.Wagner
• (Hook.) Bedd.
• Baker
• Polystichum lemmonii Underw. – Lemmon's holly fern, Shasta fern
• (D. Don) T. Moore
• Polystichum lonchitis (L.) Roth – Holly fern
• Ching & S.K.Wu
• H.Christ
• Maxon
• Polystichum luctuosum (Kunze) T. Moore – Mourning shield fern
• (Baker) Diels
• Ching & S.K.Wu
• Polystichum makinoi (Tagawa) Tagawa
• H.Christ
• Tagawa
• Ching & S.K.Wu
• Ching & S.K.Wu
• (H.Christ) Matsum.
• Polystichum mohrioides (Bory ex Willd.) C.Presl
• Ching
• N.C.Anthony & Schelpe – Mountain shield fern
• Polystichum moorei H.Christ
• Hayata
• (Franch.) Bedd.
  (=) Polystichum woodsioides H.Christ
• Polystichum munitum (Kaulf.) C. Presl – Western sword fern
  (=) Polystichum solitarium (Maxon) Underw. ex Maxon
• (L.) Fée
  (=) Polystichum moritzianum (Klotzsch) Hieron.
• Ching
• Nakai
  (=) Polystichum assurgens Ching & S.K. Wu
  (=) Polystichum yigongense Ching & S.K. Wu
• (Spreng.) C.Chr.
  (=) Polystichum atroviridissimum Hayata
• Ching & Y.P.Hsu
• (D.Don.) T.Moore
• C.Chr.
  (=) Polystichum carvifolium (Baker) Diels
• (Kunze) Liebm.
  (=) Polystichum bicolor A.R.Sm.
• Ching
• Ching
• Tagawa
• Tagawa
• Polystichum polyblepharum (Roem. ex Kunze) C.Presl – Tassel fern
  (=) Polystichum aculeatum var. japonicum (Franch. & Sav.) Diels
  (=) Polystichum setosum (Wall.) Schott
• (Wall. ex Mett.) T. Moore
  (=) Polystichum erinaceum Ching & S.K.Wu
• Hayata
  (=) Polystichum rectipinnum Hayata
• Polystichum proliferum – Mother shield fern
• Ching & S.K.Wu
  (=) Polystichum brunneum Ching & S.K.Wu
• Tagawa
• C.Chr.
  (=) Polystichum glingense Ching & Y.X.Ling
  (=) Polystichum virescens Ching & S.K.Wu
• (Kaulf.) C.Presl – Forest shield fern
  (=) Polystichum lucidum (Burm.f.) Bech.
• Ching & S.K.Wu
  (=) Polystichum tumbatzense Ching & S.K.Wu
• (Kodama) Tagawa
  (=) Polystichum aculeatum var. retrosopaleaceum Kodama
• Ching & S.K.Wu
• (Schott) Ching
  (=) Polystichum rhomboideum Schott
• Polystichum richardii (Hook.) J.Sm. – Common shield fern
• Tagawa
  (=) Polystichum platychlamys Ching
• Ching
• Polystichum scopulinum (D.C. Eaton) Maxon – Mountain holly fern, rock sword fern
  (=) Polystichum mohrioides var. scopulinum (D.C. Eaton) Fernald
• (C.B. Clarke) Ching
  (=) Polystichum nyalamense Ching
• Polystichum setiferum (Forssk.) Moore ex Woyn. – Soft shield fern
  (=) Polystichum angulare (Willd.) C. Presl
• (C. Presl) C. Presl – Alaska hollyfern
• H. Christ
  (=) Polystichum lichiangense (C.H. Wright) Ching ex H.S. Kung
• (Colenso) Diels
• Hayata
• (H.Christ) H.Christ
  (=) Polystichum atuntzeense Ching
  (=) Polystichum austrotibeticum Ching & S.K.Wu
  (=) Polystichum decorum Ching & S.K.Wu
  (=) Polystichum ellipticum Ching & S.K.Wu
  (=) Polystichum fukuyamae Tagawa
  (=) Polystichum lhasaense Ching
  (=) Polystichum parasinense Cheng-yuan Yang
  (=) Polystichum wilsoni H.Christ
• (D.Don) Fée
  (=) Polystichum apicisterile Ching & S.K.Wu
  (=) Polystichum integripinnulum Ching
• H.Christ
  var. conaense (=) Polystichum conaense Ching & S.K.Wu
• (Kunze ex Mett.) Bedd.
  (=) Polystichum ilicifolium (D. Don) T. Moore
• (H. Christ) Diels
  (=) Polystichum paradoxum Ching & Y.P.Hsu
• (Kunze) T. Moore
  (=) Polystichum heteropaleaceum N.C. Nair & Nag
  (=) Polystichum kodamae Tagawa
• (Hook.f.) Bedd.
• Ching
• N.C.Anthony – Stemmed shield fern
• (Kunze) C.Presl
• Polystichum tsus-simense (Hook.) J.Sm. – Korean rock fern
  (=) Polystichum falcilobum Ching
• Polystichum vestitum (G.Forst.) C.Presl – Prickly shield fern
• (Bedd.) C.Chr.
• Polystichum whiteleggei Watts
• (Baker) Diels
  (=) Polystichum monotis (H.Christ) C.Chr.
  (=) Polystichum praelongum H.Christ
• Ching & S.K.Wu
• H.Christ
  (=) Polystichum gyirongense Ching
  (=) Polystichum jizhushanense Ching

Polystichum munitum

Hybrids

Hybridisation is frequent in the genus, with several named hybrids, including:-

• P. × bicknellii (P. aculeatum × P. setiferum)
• P. × illyricum (P. aculeatum × P. lonchitis)
• P. × lonchitiforme (P. lonchitis × P. setiferum)
• P. × lesliei (P. setiferum × P. munitum) first found in Surrey in 1995 and a second plant found in Cornwall in 2001.
• P. × potteri (P. braunii × P. acrostichoides)

Former species

Species that were at one time considered part of the genus Polystichum, but are now categorized elsewhere, include:

• Polystichum auriculatum (L.) C.Presl 1836 = (L.) Kuntze 1891
• Polystichum falcatum (L.f.) Diels 1899 = Cyrtomium falcatum (L.f.) C.Presl – Japanese Holly Fern
• Polystichum lepidocaulon (Hook.) J.Sm. 1866 = (Hook.) Ching 1940

Distribution

With species in six continents and many islands, Polystichum is remarkable for its global spread. Polystichum ferns first emerged in Asia during the late Eocene, around 49 million years ago. During this period there were high temperatures across the globe, which may have contributed to the diversification of flora.

Polystichum's spread to the New World took place during the late Eocene to early Oligocene. The most likely dispersal method was across a paratropical forest on a Pacific Ocean land bridge, such as the Bering Land Bridge. For a period before the height of the Ice Age temperatures froze enough seawater to lower the sea level but still allowed a forest to grow in Northern latitudes. From there Polystichum was able to spread through North American and into Central America.

Original theories described Polystichum spreading further into South America from Central America, but recent research has shown that South American Polystichum instead spread through long-distance dispersal from Australia. Genetic study has revealed close evolutionary relationships between Polystichum species in these two areas. Both Austral and Austral South American species lack and indusium. Austral Polystichum lack cilia, while South American species have marginal cilia.

Hawaiian Polystichum also spread through long-distance dispersal, with two separate dispersal events leading to the three Polystichum now observed in Hawaii.

Ecology

Polystichum species are used as food plants by the larvae of some Lepidoptera species including Pharmacis fusconebulosa. Specimens of some of these can be found at the Royal Botanic Gardens, Sydney.

Cultivation

Several species are grown as ornamental plants in gardens, notably P. setiferum. One species, P. tsus-simense of eastern Asia, is commonly offered as a houseplant.

References

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External links

Wikimedia Commons has media related to Polystichum.

• Data related to Polystichum at Wikispecies
• Jepson Manual Treatment
• the Polystichum homepage