Polystichum

Polystichum is a genus of ferns in the family Dryopteridaceae, subfamily Dryopteridoideae, according to the Pteridophyte Phylogeny Group classification of 2016. 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, North America, and Europe have much lower diversity. Polystichum species are terrestrial or rock-dwelling ferns of warm-temperate and montane-tropical 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 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

, 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 originally defined a monophyletic Polystichum s.s. by removing Cyrtomium as its own genus. It was further separated by Li et al. 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 2020, 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.

– Christmas fern
– Hard shield fern

– Aleutian shield fern
– Anderson's hollyfern
Polystichum atkinsonii
Polystichum australiense
Polystichum bakerianum
Polystichum biaristatum
Polystichum bomiense
Polystichum bonapartii
Polystichum bonseyi – Bonsey's Hollyfern
Polystichum brachypterum – Rusty swordfern
Polystichum braunii – Braun's shield fern, Braun's hollyfern
Polystichum brachypterum

Polystichum garhwalicum

Polystichum bulbiferum
Polystichum calderonense – Monte Guilarte hollyfern
Polystichum californicum – California sword fern
Polystichum capillipes

Polystichum michelii
Polystichum minusculum
Polystichum molliculum

Polystichum castaneum
Polystichum chilense
Polystichum christii
Polystichum chunii
Polystichum craspedosorum
Polystichum cyclolobum
Polystichum cystostegia – Alpine shield fern
Polystichum deltodon
Polystichum dielsii
Polystichum discretum
Polystichum drepanum
Polystichum dudleyi – Dudley's sword fern
Polystichum duthiei

Polystichum tsuchuense

Polystichum echinatum – Rusty swordfern
Polystichum erosum
Polystichum excellens
Polystichum eximium

Polystichum tialooshanense

Polystichum falcatipinnum
Polystichum falcinellum
Polystichum fallax
Polystichum formosanum
Polystichum glandulosum
Polystichum gongboense

Polystichum rarum

Polystichum grandifrons

Polystichum kiusiuense

Polystichum gymnocarpium
Polystichum haleakalense – Island swordfern
Polystichum hancockii
Polystichum hecatopteron
Polystichum herbaceum
Polystichum imbricans – Narrowleaf sword fern
Polystichum incongruum
Polystichum kruckebergii – Kruckeberg's sword fern/holly fern
Polystichum kwakiutlii
Polystichum lachenense
Polystichum lanceolatum
Polystichum lemmonii – Lemmon's holly fern, Shasta fern
Polystichum lentum
Polystichum lonchitis – Holly fern
Polystichum longidens
Polystichum longipaleatum
Polystichum longipes
Polystichum luctuosum – Mourning shield fern
Polystichum macleae
Polystichum macrochlaenum
Polystichum makinoi
Polystichum martini
Polystichum mayebarae
Polystichum mediocre
Polystichum medogense
Polystichum microchlamys
Polystichum mohrioides
Polystichum mollissimum
Polystichum monticola – Mountain shield fern
Polystichum moorei
Polystichum morii
Polystichum moupinense

Polystichum woodsioides

Polystichum munitum – Western sword fern

Polystichum solitarium

Polystichum muricatum

Polystichum moritzianum

Polystichum nakenense
Polystichum neolobatum

Polystichum assurgens
Polystichum yigongense

Polystichum nepalense

Polystichum atroviridissimum

Polystichum ningshenense
Polystichum obliquum
Polystichum omeiense

Polystichum carvifolium

Polystichum ordinatum

Polystichum bicolor

Polystichum orientalitibeticum
Polystichum paramoupinense
Polystichum parvipinnulum
Polystichum piceopaleaceum
Polystichum polyblepharum – Tassel fern

Polystichum aculeatum var. japonicum
Polystichum setosum

Polystichum prescottianum

Polystichum erinaceum

Polystichum prionolepis

Polystichum rectipinnum

Polystichum proliferum – Mother shield fern
Polystichum pseudocastaneum

Polystichum brunneum

Polystichum pseudomakinoi
Polystichum punctiferum

Polystichum glingense
Polystichum virescens

Polystichum pungens – Forest shield fern

Polystichum lucidum

Polystichum qamdoense

Polystichum tumbatzense

Polystichum retrosopaleaceum

Polystichum aculeatum var. retrosopaleaceum

Polystichum rhombiforme
Polystichum rhomboidea

Polystichum rhomboideum

Polystichum richardii – Common shield fern
Polystichum rigens

Polystichum platychlamys

Polystichum rotundilobum
Polystichum scopulinum – Mountain holly fern, rock sword fern

Polystichum mohrioides var. scopulinum

Polystichum semifertile

Polystichum nyalamense

Polystichum setiferum – Soft shield fern

Polystichum angulare

Polystichum setigerum – Alaska hollyfern
Polystichum shensiense

Polystichum lichiangense

Polystichum silvaticum
Polystichum simplicipinnum
Polystichum sinense

Polystichum atuntzeense
Polystichum austrotibeticum
Polystichum decorum
Polystichum ellipticum
Polystichum fukuyamae
Polystichum lhasaense
Polystichum parasinense
Polystichum wilsoni

Polystichum squarrosum

Polystichum apicisterile
Polystichum integripinnulum

Polystichum stenophyllum

var. conaense ''Polystichum conaense

Polystichum stimulans

Polystichum ilicifolium

Polystichum submite

Polystichum paradoxum

Polystichum tacticopterum

Polystichum heteropaleaceum
Polystichum kodamae

Polystichum thomsoni
Polystichum tibeticum
Polystichum transvaalense – Stemmed shield fern
Polystichum tripteron
Polystichum tsus-simense – Korean rock fern

Polystichum falcilobum

Polystichum vestitum – Prickly shield fern
Polystichum wattii
Polystichum whiteleggei
Polystichum xiphophyllum

Polystichum monotis
Polystichum praelongum

Polystichum yadongense
Polystichum yunnanense

Polystichum gyirongense
Polystichum jizhushanense
Image:Polystichum munitum 1.jpg|thumb|left|222px|Polystichum munitum''

Hybrids

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

P. × bicknellii
P. × illyricum
P. × lonchitiforme
P. × lesliei first found in Surrey in 1995 and a second plant found in Cornwall in 2001.
P. × ''potteri''