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.

Description

Many ferns of this genus have stout, slowly creeping rootstocks that form a crown, with a vase-like ring of evergreen fronds Template:Convert 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; Template:As of, 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. Template:Div col

• Template:Txil
• Template:Txil – Christmas fern
• Template:Txil – Hard shield fern
• Template:Txil
• Template:Txil
  (=) Template:Tx
• Template:Txil
• Template:Txil – Aleutian shield fern
• Template:Txil – Anderson's hollyfern
• Polystichum atkinsonii Template:Au
• Polystichum australiense Template:Au
• Polystichum bakerianum Template:Au
• Polystichum biaristatum Template:Au
• Polystichum bomiense Template:Au
• Polystichum bonapartii Template:Au
• Polystichum bonseyi Template:Au – Bonsey's Hollyfern
• Polystichum brachypterum Template:Au – Rusty swordfern
• Polystichum braunii Template:Au – Braun's shield fern, Braun's hollyfern
• Polystichum brachypterum Template:Au
  (=) Polystichum garhwalicum Template:Au
• Polystichum bulbiferum Template:Au
• Polystichum calderonense Template:Au – Monte Guilarte hollyfern
• Polystichum californicum Template:Au – California sword fern
• Polystichum capillipes Template:Au
  (=) Polystichum michelii Template:Au
  (=) Polystichum minusculum Template:Au
  (=) Polystichum molliculum Template:Au
• Polystichum castaneum Template:Au
• Polystichum chilense Template:Au
• Polystichum christii Template:Au
• Polystichum chunii Template:Au
• Polystichum craspedosorum Template:Au
• Polystichum cyclolobum Template:Au
• Polystichum cystostegia Template:Au – Alpine shield fern
• Polystichum deltodon Template:Au
• Polystichum dielsii Template:Au
• Polystichum discretum Template:Au
• Polystichum drepanum Template:Au
• Polystichum dudleyi Template:Au – Dudley's sword fern
• Polystichum duthiei Template:Au
  (=) Polystichum tsuchuense Template:Au
• Polystichum echinatum Template:Au – Rusty swordfern
• Polystichum erosum Template:Au
• Polystichum excellens Template:Au
• Polystichum eximium Template:Au
  (=) Polystichum tialooshanense Template:Au
• Polystichum falcatipinnum Template:Au
• Polystichum falcinellum Template:Au
• Polystichum fallax Template:Au
• Polystichum formosanum Template:Au
• Polystichum glandulosum Template:Au
• Polystichum gongboense Template:Au
  (=) Polystichum rarum Template:Au
• Polystichum grandifrons Template:Au
  (=) Polystichum kiusiuense Template:Au
• Polystichum gymnocarpium Template:Au
• Polystichum haleakalense Template:Au – Island swordfern
• Polystichum hancockii Template:Au
• Polystichum hecatopteron Template:Au
• Polystichum herbaceum Template:Au
• Polystichum imbricans Template:Au – Narrowleaf sword fern
• Polystichum incongruum Template:Au
• Polystichum kruckebergii Template:Au – Kruckeberg's sword fern/holly fern
• Polystichum kwakiutlii Template:Au
• Polystichum lachenense Template:Au
• Polystichum lanceolatum Template:Au
• Polystichum lemmonii Template:Au – Lemmon's holly fern, Shasta fern
• Polystichum lentum Template:Au
• Polystichum lonchitis Template:Au – Holly fern
• Polystichum longidens Template:Au
• Polystichum longipaleatum Template:Au
• Polystichum longipes Template:Au
• Polystichum luctuosum Template:Au – Mourning shield fern
• Polystichum macleae Template:Au
• Polystichum macrochlaenum Template:Au
• Polystichum makinoi Template:Au
• Polystichum martini Template:Au
• Polystichum mayebarae Template:Au
• Polystichum mediocre Template:Au
• Polystichum medogense Template:Au
• Polystichum microchlamys Template:Au
• Polystichum mohrioides Template:Au
• Polystichum mollissimum Template:Au
• Polystichum monticola Template:Au – Mountain shield fern
• Polystichum moorei Template:Au
• Polystichum morii Template:Au
• Polystichum moupinense Template:Au
  (=) Polystichum woodsioides Template:Au
• Polystichum munitum Template:Au – Western sword fern
  (=) Polystichum solitarium Template:Au
• Polystichum muricatum Template:Au
  (=) Polystichum moritzianum Template:Au
• Polystichum nakenense Template:Au
• Polystichum neolobatum Template:Au
  (=) Polystichum assurgens Template:Au
  (=) Polystichum yigongense Template:Au
• Polystichum nepalense Template:Au
  (=) Polystichum atroviridissimum Template:Au
• Polystichum ningshenense Template:Au
• Polystichum obliquum Template:Au
• Polystichum omeiense Template:Au
  (=) Polystichum carvifolium Template:Au
• Polystichum ordinatum Template:Au
  (=) Polystichum bicolor Template:Au
• Polystichum orientalitibeticum Template:Au
• Polystichum paramoupinense Template:Au
• Polystichum parvipinnulum Template:Au
• Polystichum piceopaleaceum Template:Au
• Polystichum polyblepharum Template:Au – Tassel fern
  (=) Polystichum aculeatum var. japonicum Template:Au
  (=) Polystichum setosum Template:Au
• Polystichum prescottianum Template:Au
  (=) Polystichum erinaceum Template:Au
• Polystichum prionolepis Template:Au
  (=) Polystichum rectipinnum Template:Au
• Polystichum proliferum – Mother shield fern
• Polystichum pseudocastaneum Template:Au
  (=) Polystichum brunneum Template:Au
• Polystichum pseudomakinoi Template:Au
• Polystichum punctiferum Template:Au
  (=) Polystichum glingense Template:Au
  (=) Polystichum virescens Template:Au
• Polystichum pungens Template:Au – Forest shield fern
  (=) Polystichum lucidum Template:Au
• Polystichum qamdoense Template:Au
  (=) Polystichum tumbatzense Template:Au
• Polystichum retrosopaleaceum Template:Au
  (=) Polystichum aculeatum var. retrosopaleaceum Template:Au
• Polystichum rhombiforme Template:Au
• Polystichum rhomboidea Template:Au
  (=) Polystichum rhomboideum Template:Au
• Polystichum richardii Template:Au – Common shield fern
• Polystichum rigens Template:Au
  (=) Polystichum platychlamys Template:Au
• Polystichum rotundilobum Template:Au
• Polystichum scopulinum Template:Au – Mountain holly fern, rock sword fern
  (=) Polystichum mohrioides var. scopulinum Template:Au
• Polystichum semifertile Template:Au
  (=) Polystichum nyalamense Template:Au
• Polystichum setiferum Template:Au – Soft shield fern
  (=) Polystichum angulare Template:Au
• Polystichum setigerum Template:Au – Alaska hollyfern
• Polystichum shensiense Template:Au
  (=) Polystichum lichiangense Template:Au
• Polystichum silvaticum Template:Au
• Polystichum simplicipinnum Template:Au
• Polystichum sinense Template:Au
  (=) Polystichum atuntzeense Template:Au
  (=) Polystichum austrotibeticum Template:Au
  (=) Polystichum decorum Template:Au
  (=) Polystichum ellipticum Template:Au
  (=) Polystichum fukuyamae Template:Au
  (=) Polystichum lhasaense Template:Au
  (=) Polystichum parasinense Template:Au
  (=) Polystichum wilsoni Template:Au
• Polystichum squarrosum Template:Au
  (=) Polystichum apicisterile Template:Au
  (=) Polystichum integripinnulum Template:Au
• Polystichum stenophyllum Template:Au
  var. conaense (=) Polystichum conaense Template:Au
• Polystichum stimulans Template:Au
  (=) Polystichum ilicifolium Template:Au
• Polystichum submite Template:Au
  (=) Polystichum paradoxum Template:Au
• Polystichum tacticopterum Template:Au
  (=) Polystichum heteropaleaceum Template:Au
  (=) Polystichum kodamae Template:Au
• Polystichum thomsoni Template:Au
• Polystichum tibeticum Template:Au
• Polystichum transvaalense Template:Au – Stemmed shield fern
• Polystichum tripteron Template:Au
• Polystichum tsus-simense Template:Au – Korean rock fern
  (=) Polystichum falcilobum Template:Au
• Polystichum vestitum Template:Au – Prickly shield fern
• Polystichum wattii Template:Au
• Polystichum whiteleggei Template:Au
• Polystichum xiphophyllum Template:Au
  (=) Polystichum monotis Template:Au
  (=) Polystichum praelongum Template:Au
• Polystichum yadongense Template:Au
• Polystichum yunnanense Template:Au
  (=) Polystichum gyirongense Template:Au
  (=) Polystichum jizhushanense Template:Au

File:Polystichum munitum 1.jpg

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 Template:Au = Dryopteris auriculata Template:Au
• Polystichum falcatum Template:Au = Cyrtomium falcatum Template:Au – Japanese Holly Fern
• Polystichum lepidocaulon Template:Au = Cyrtomidictyum lepidocaulon Template:Au

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.

External links

• Template:Wikispecies-inline
• Jepson Manual Treatment
• the Polystichum homepage