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.
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.
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.
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). The plants were thought to cause infertility in women.
Vitruvius relates the story of the name thus:
... certain pastures in Crete, on each side of the river Pothereus, which separates the two Cretan states of Gnosus and Gortyna. There are cattle at pasture on the right and left banks of that river, but while the cattle that feed near Gnosus have the usual spleen, those on the other side near Gortyna have no perceptible spleen. On investigating the subject, physicians discovered on this side a kind of herb which the cattle chew and thus make their spleen small. The herb is therefore gathered and used as a medicine for the cure of splenetic people. The Cretans call it ἄσπληνον.
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
Asplenium adiantum-nigrum L. – black spleenwort (= A. lucidum Burm.f.)
Asplenium adiantum-nigrum ssp. adiantum-nigrum
Asplenium adiantum-nigrum ssp. serpentini (Tausch) Koch
Asplenium adulterinum Milde – ladder spleenwort
Asplenium aequibasis
Asplenium aethiopicum
Asplenium africanum
Asplenium × alternifolium Wulf.
Asplenium anceps
Asplenium angustum Sw.
Asplenium antiquum Makino
Asplenium ascensionis S.Watson
Asplenium attenuatum R.Br.
Asplenium aureum (sometimes in Ceterach)
Asplenium auritum
Asplenium australasicum (J.Sm.) Hook. – crow's-nest fern
Asplenium australasicum f. australasicum
Asplenium australasicum f. robinsonii
Asplenium azoricum Lovis, Rasbach & Reichst.
Asplenium bifrons
Asplenium billottii – lanceolate spleenwort
Asplenium bipinnatifidum
Asplenium brachycarpum
Asplenium bradleyi
Asplenium bulbiferum – mother spleenwort, hen and chickens fern, mouku (Māori)
Asplenium carnarvonense - Brownsey
Asplenium caudatum
Asplenium ceterach – rustyback fern (sometimes in Ceterach)
Asplenium chathamense Brownsey
Asplenium chihuahuense Baker
Asplenium compressum Sw.
Asplenium congestum
Asplenium corderoanum
Asplenium crinicaule
Asplenium cristatum
Asplenium cuneifolium Viv. (= A. forsteri auct. non Sadl.) – serpentine spleenwort
Asplenium cymbifolium
Asplenium daghestanicum H.Christ – Dagestanian spleenwort
Asplenium dalhousiae (sometimes in Ceterach)
Asplenium dareoides
Asplenium daucifolium – Mauritius spleenwort
Asplenium difforme R.Br.
Asplenium fissum
Asplenium dimorphum – Norfolk Island Spleenwort
Asplenium divaricatum
Asplenium dregeanum
Asplenium × ebenoides R.R.Scott
Asplenium ecuadorense Stolze
Asplenium feei Kunze ex Fée
Asplenium fissum
Asplenium flabellifolium – necklace fern
Asplenium flaccidum G.Forst. – weeping spleenwort, hanging spleenwort
Asplenium fontanum (L.) Bernh. – smooth rock spleenwort
Asplenium forisiense – rock spleenwort
Asplenium formosum
Asplenium gemmiferum Schrad.
Asplenium × germanicum
Asplenium gueinzii Mett.
Asplenium goudeyi Lord Howe Island
Asplenium haughtonii – Barn Fern
Asplenium hemionitis
Asplenium hermannii-christii Fomin – Hermann Christ's asplenium
Asplenium hookerianum Colenso
Asplenium hybridum
Asplenium incisum
Asplenium × jacksonii Alston – Jackson's spleenwort (sterile, triploid hybrid between Asplenium adiantum-nigrum and Asplenium scolopendrium)
Asplenium × kenzoi - oni-hinokishida, cultivated in Japan
Asplenium komarovii - Akasawa
Asplenium laciniatum
Asplenium lamprophyllum Carse
Asplenium laserpitiifolium – Johnston River fern
Asplenium lepidum C.Presl
Asplenium listeri – Christmas Island spleenwort
Asplenium longissimum
Asplenium lucidum
Asplenium lunulatum – Hen-and-chicks
Asplenium lyallii
Asplenium macedonicum
Asplenium majoricum
Asplenium marinum – sea spleenwort
Asplenium × microdon T Moore – Moore's spleenwort (hybrid between Asplenium scolopendrium and Asplenium obovatum subsp lanceolatum)
Asplenium milnei Carruth
Asplenium montanum – mountain spleenwort
Asplenium musifolium
Asplenium nidus – bird's-nest fern
Asplenium normale
Asplenium obliquum
Asplenium oblongifolium Colenso – shining spleenwort (= A. lucidum auct. non Burm.f., sensu G.Forst.)
Asplenium obovatum
Asplenium obtusatum G.Forst.
Asplenium obtusatum ssp. northlandicum (Brownsey) Ogle (possibly distinct species)
Asplenium obtusatum 'Chile' (possibly distinct species, sometimes included in A. obliquum)
Asplenium oligolepidum C.Chr. (= A. lucidum auct. non Burm.f., sensu G.Forst.)
Asplenium oligophlebium
Asplenium onopteris L. – western black spleenwort, Irish spleenwort (sometimes included in A. adiantum-nigrum)
Asplenium pacificum
Asplenium paleaceum R.Br. – chaffy spleenwort
Asplenium palmeri
Asplenium parvum
Asplenium petrarchae
Asplenium pinnatifidum – lobed spleenwort
Asplenium planicaule
Asplenium platybasis Kunze ex Mett.
Asplenium platyneuron – ebony spleenwort
Asplenium polyodon G.Forst. – sickle spleenwort
Asplenium praemorsum
Asplenium prolongatum Hook.
Asplenium pteridoides Baker
Asplenium resiliens – black-stemmed spleenwort
Asplenium rhizophyllum – American walking fern (sometimes in Camptosorus)
Asplenium richardii
Asplenium ruprechtii – Asian walking fern (sometimes in Camptosorus)
Asplenium ruta-muraria L. – wall-rue
Asplenium rutifolium
Asplenium sagittatum – Mule's spleenwort (sometimes in Phyllitis)
Asplenium sandersonii Hook.
Asplenium × sarniense Sleep Guernsey Spleenwort
Asplenium schizotrichum Copel.
Asplenium schweinfurthii
Asplenium scleroprium
Asplenium scolopendrium – hart's-tongue fern (sometimes in Phyllitis)
Asplenium scolopendrium var. americanum – American Hart's-tongue
Asplenium seelosii
Asplenium septentrionale – forked spleenwort, northern spleenwort
Asplenium septentrionale × trichomanes Wulf.
Asplenium serra
Asplenium serratum – wild bird's-nest fern
Asplenium sessilifolium
Asplenium shuttleworthianum Kunze
Asplenium simplicifrons F.Muell.
Asplenium splendens
Asplenium surrogatum P.S.Green
Asplenium tenerum G.Forst.
Asplenium terrestre
Asplenium theciferum (Kunth) Mett.
Asplenium thunbergii
Asplenium trichomanes – maidenhair spleenwort
Asplenium trichomanes ssp. quadrivalens D.E. Meyer
Asplenium trichomanes ssp. trichomanes
Asplenium trichomanes subsp. coriaceifolium
Asplenium trilobum Cav.
Asplenium tutwilerae B.R.Keener & L.J.Davenport
Asplenium vespertinum
Asplenium vieillardii Mett.
Asplenium virens
Asplenium viride – green spleenwort
Asplenium vittiforme
Asplenium viviparum
See also
Mount Asplenium
Phyllocladus aspleniifolius (Celery-top Pine, a conifer with Asplenium-like leaves)
Asplenium hybrids
References
Epiphytes
Fern genera
Taxa named by Carl Linnaeus