Polystichum

Location & distribution maps

Phylogeny & links to associated information

Wikipedia links:       Monilophytes > Polypodiales > Dryopteridaceae > Polystichum

Other links:    

Species:   P australiaense   P proliferum

Plant  information

Common name:         Shield Ferns 

Conservation status: ...

Etymology:   

• The genus name Polystichum is derived from Greek:

  • poly - many

  • stichos - rows referring to the many rows of sori

Spores:                            

• The sori are round, with a circular indusium, except in South American species which lack an indusium

• The genus differs from the allied fern genus Dryopteris in the indusium being circular, not reniform

Leaves:         

• 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 cm long

• The genus differs from Dryopteris in having the leaf segments with auricles—asymmetrical blades where one side of the segment is much longer than the other at the base

Stem & branches: 

• The stipes have prominent scales with often have hair-like cilia, but lack any true hairs

Roots:         

• Many ferns of this genus have stout, slowly creeping rootstocks that form a crown, with a vase-like ring of evergreen fronds 

Habit:        

• Fern

Habitat:   

• Terrestrial or rock-dwelling ferns of warm-temperate and montane-tropical regions

• A few species grow in alpine regions

• Often found in disturbed habitats such as road cuts, talus slopes, and stream banks

Distribution:                  

• Cosmopolitan 

  • Eastern Asia: 208 species in China alone

  • Mexico to Brazil:  >= 100 species

  • Africa: > +   17 species

  • North America: >=   18 species

  • Europe: >=      5 species

Species:                     

• World:           ~ 500 

• Australia:          4 ... ?

Additional notes:     

• 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

  • 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:

Sources of information:

• https://en.wikipedia.org/wiki/Polystichum (2023)