Asplenium

Asplenium is a genus of about 700 species of ferns, often treated as the only genus in the family Aspleniaceae, though other authors consider Hymenasplenium separate, based on molecular phylogenetic analysis of DNA sequences, a different chromosome count, and structural differences in the rhizomes. The type species for the genus is Asplenium marinum.

Asplenium
Maidenhair spleenwort (Asplenium trichomanes ssp. quadrivalens)
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Class: Polypodiopsida
Order: Polypodiales
Suborder: Aspleniineae
Family: Aspleniaceae
Genus: Asplenium
L.
Type species
Asplenium marinum
Species

About 700, but see text.

Synonyms
  • Camptosorus
  • Ceterach
  • Loxoscaphe T.Moore
  • Phyllitis
  • Tarachia

and see text

The most common vernacular name is spleenworts, applied to the more "typical" species. A. nidus and several similar species are called bird's-nest ferns, the Camptosorus group is known as walking ferns, and distinct names are applied to some other particularly well-known species.

Taxonomy and genetics

Many groups of species have been separated from Asplenium as segregate genera. These include Camptosorus, Ceterach, Phyllitis, and Tarachia, but these species can form hybrids with other Asplenium species and because of this are usually included in a more broadly defined Asplenium.[1]

Some of the older classifications elevate the Aspleniaceae to the taxonomic rank of order as Aspleniales. The newer classifications place it in the subordinal group called eupolypods within the order Polypodiales. Within the eupolypods, Aspleniaceae belongs to a clade informally and provisionally known as eupolypods II.

It has been found that in some species, the chloroplast genome has evolved in complex and highly unusual ways. This makes standard cladistic analyses unsuited to resolve the phylogeny of that particular group of ferns, and even very sophisticated computational phylogenetics methods yield little information. In addition to hybridization running rampant in parts of this genus, there are also some species like the mother spleenwort (A. bulbiferum) or A. viviparum which mainly reproduce asexually, essentially cloning themselves over and over again. While most are diploid or tetraploid, some species (e.g. A. shuttleworthianum) are octoploid.[2]

Uses

Both the scientific name and the common name "spleenwort" are derived from an old belief, based on the doctrine of signatures, that the fern was useful for ailments of the spleen, due to the spleen-shaped sori on the backs of the fronds. "-wort" is an ancient English term that simply means "plant" (compare German -wurz).

A few of these ferns have some economic importance in the horticulture trade. The bird's-nest ferns (A. nidus and several very similar, closely related species) are commonly found for sale as a house plant. The Australian mother spleenwort (A. bulbiferum) is sometimes available at greenhouses, and is of interest, along with the related A. viviparum, for the many small bulblets borne on the fronds that may grow into new plants. This characteristic is also shared with the eastern North American walking fern (A. rhizophyllum) and several Mexican species including A. palmeri. The ebony spleenwort A. platyneuron is also sometimes sold in nurseries as a hardy plant. However, many spleenworts are epipetric or epiphytic and difficult to cultivate.

Asplenium species are used as food plants by the larvae of some Lepidoptera species including Batrachedra bedelliella which feeds exclusively on A. nidus. For diseases of Asplenium, see List of foliage plant diseases (Polypodiaceae).

Selected species
Black spleenwort (A. adiantum-nigrum)
Asplenium aethiopicum
Crow's-nest fern (A. australasicum), one of the bird's-nest ferns
Asplenium azoricum
Sea spleenwort (A. marinum)
Forked spleenwort (A. septentrionale)
Green spleenwort (A. viride)
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See also

References
  1. Schneider, Harald; Russell, Steve J.; Cox, Cymon J.; Bakker, Freek; Henderson, Sally; Rumsey, Fred; Barrett, John; Gibby, Mary; Vogel, Johannes C. (2004). "Chloroplast Phylogeny of Asplenioid Ferns based on rbcL and trnL-F Spacer Sequences (Polypodiidae, Aspleniaceae) and its Implications for Biogeography". Systematic Botany. 29 (2): 260–274. doi:10.1600/036364404774195476.
  2. Lara D. Shepherd, Barbara R. Holland & Leon R. Perrie (2008). "Conflict amongst chloroplast DNA sequences obscures the phylogeny of a group of Asplenium ferns". Molecular Phylogenetics and Evolution. 48 (1): 176–187. doi:10.1016/j.ympev.2008.02.023. PMID 18462954.
  3. Murphy, Rosaline J; Page, Cristopher N; Parslow, Rosemary E; Bennallick, Ian J (2012). Ferns, Clubmosses, Quillworts and Horsetails of Cornwall and the Isles of Scilly. Truro: ERCCIS. ISBN 978-1-902864-07-5.
  4. "Asplenium × kenzoi". Germplasm Resources Information Network (GRIN). Agricultural Research Service (ARS), United States Department of Agriculture (USDA). Retrieved December 15, 2017.
  5. N. Murakami; S. Nogami; M. Watanabe; K. Iwatsuki (1999). "Phylogeny of Aspleniaceae inferred from rbcL nucleotide sequences". American Fern Journal. 89 (4): 232–243. doi:10.2307/1547233. JSTOR 1547233.
  6. "The list of plant and animal species for which the status of natural rarities was established". Retrieved August 26, 2010.
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