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Asplenium ascensionis

Overview

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Near Threatened

Threat status

Interesting Facts

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Description

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Family Aspleniaceae

Plants terrestrial , on rock, or rarely epiphytic. Stems erect or nearly erect, rarely long-creeping, scaly . Steles radially symmetric or dorsiventral (with structurally distinct abaxial and adaxial aspects ) dictyosteles. Leaves monomorphic , rarely almost dimorphic with fertile leaves taller and more erect than sterile ones. Petioles with 1 vascular bundle X-shaped in cross section or with 2 vascular bundles back to back and C-shaped. Blades extremely diverse , simple to 4-pinnate, commonly with tiny glandular hairs and a few linear scales , rarely with spreading hairs. Veins free to anastomosing. Sori borne on veins, ± lunate to linear . Indusia usually present, shape conforming to sorus and originating along 1 side of sorus. Sporangia with stalk of 1 row of cells , annulus vertical , interrupted by sporangial stalk. Spores monolete; perispore typically winged , spiny , reticulate , or perforate . Gametophytes surficial , green, cordate.

Genera 1, species ca. 700 (1 genus, 28 species, and 3 nothospecies in the flora ) : worldwide.

Members of this family can usually be identified by the combination of clathrate stem scales and indusiate linear sori. Supporting anatomic characteristics include the two vascular bundles in the petiole that unite distally in the petiole to form an X-shaped petiolar strand , and the single row of cells in the sporangial stalk. The scales consist of cells with dark, thick, radial walls and clear, thin, tangential walls, giving the scales a clathrate (latticelike) appearance reminiscent of lead moldings between plates of stained glass.

As construed here, Aspleniaceae comprise a single, huge, extremely diverse genus, Asplenium . A satisfactory taxonomic division into subgenera or satellite genera has not been possible because of the absence of any significant gaps . Various segregates have been proposed (e.g. , Camptosorus, Phyllitis, Ceterach, Pleurosorus ), but numerous "intergeneric" hybrids occur.

The members of Asplenium are popular with plant evolutionists, field naturalists, and fern gardeners, not only because of the interesting morphology of the plants but also because of their remarkable ability to form spectacular hybrids, often combining dramatically different leaf shapes. In North America, 23 diploid hybrids and allopolyploids have been recorded. At least two of these hybrid combinations occur as both sterile diploids and their fertile allotetraploid derivatives. Only those hybrids that are reproductively competent (through vigorous clone-forming by root proliferations or apogamy, or rarely through sexual reproduction) are treated in the key and fully described below.

Only about two-fifths of the reproductively competent species are believed to be cladistically divergent species; the other three-fifths are of hybrid origin (allopolyploids) . For two of the allotetraploids, sterile diploids of the same parentage are also known. The most unusual allopolyploid phytogeographically is Asplenium adiantum-nigrum, the parents of which are known only in the Old World. These reticulate relationships are summarized in the reticulogram.

Polyploidy is widespread in Asplenium, and the chromosome numbers vary from 2 x to 6 x . Two species, Asplenium trichomanes and A . heterochroum, occur in different levels of polyploidy---2 x and 4 x, and 4 x and 6 x, respectively. The highest chromosome number known for Asplenium in North America is 2 n = 216 (in A . trichomanes-dentatum and the hexaploid form of A . heterochroum ) . The only three apogamous taxa are A . monanthes (3 x ), A . resiliens (3 x ), and A . × heteroresiliens (5 x ) .[1]

Genus Asplenium

Roots fibrous , not proliferous or proliferous and producing tiny plantlets . Stems erect , rarely long-creeping; scales basally attached, clathrate. Petioles not articulate . Blades 1--4-pinnate, of diverse size and shape . Indusia present. x = 36.

Species ca. 700 (28 species, 3 nothosp: worldwide.[2]

Habitat

Biome: Terrestrial [3].

Ecology: Although localised to the Green Mountain area, it can be the dominant species where it occurs. A. ascensionis seems to be able to persist with some introduced vegetation in species poor communities. However, A. ascensionis is no longer found as a component of the ground vegetation and few specimens attain the large size of Hookers collection (Cronk 1980), and has therefore suffered reduction in distribution to some extent. A. ascensionis inhabits stone as well as cinder walls and is found in more sheltered locations that are rarely completely exposed to solar radiation .[3].

List of Habitats :

Taxonomy

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Notes

Publishing author : Watson Publication : Proc. Am. Acad. 26. 163. 1891 1891

Similar Species

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Members of the genus Asplenium

ZipcodeZoo has pages for 165 species, subspecies, varieties, forms, and cultivars in this genus. Here are just 100 of them:

A. abscissum (Abscised Spleenwort) · A. acuminatum (Taper-Tip Spleenwort) · A. adiantum-nigrum (Black Spleenwort) · A. adiantum-nigrum woronowii (Black Spleenwort) · A. adulterinum (Ladder Spleenwort) · A. aethiopicum (Egyptian Spleenwort) · A. alternifolium (Alternateleaf Spleenwort) · A. auriculatum (Tree-Trunk Spleenwort) · A. auritum (Auricled Spleenwort) · A. auritum Sw. var. auritum Sw. (Eared Spleenwort) · A. auritum Sw. var. bipinnatifidum Kunze (Eared Spleenwort) · A. auritum var. auritum (Eared Spleenwort) · A. auritum var. bipinnatifidum (Eared Spleenwort) · A. australasicum (Birds Nest Fern) · A. australasicum forma australasicum (Bird´s-Nest Fern) · A. australasicum f. robinsonii (Bird´s-Nest Fern) · A. biscaynianum (Biscayne Spleenwort) · A. boydstoniae (Boydston's Spleenwort) · A. bradleyi (Bradley's Spleenwort) · A. bulbiferum (Hen and Chickens Fern) · A. caudatum (Speenwort) · A. ceterach (Rusty-Back Fern) · A. cirrhatum (Chestnut Scale Spleenwort) · A. clermontiae (Clermont's Spleenwort) · A. contiguum (Forest Spleenwort) · A. contiguum Kaulf. var. contiguum Kaulf. (Forest Spleenwort) · A. contiguum Kaulf. var. hirtulum C.Chr. (Forest Spleenwort) · A. contiguum var. contiguum (Forest Spleenwort) · A. contiguum var. hirtulum (Forest Spleenwort) · A. corderoanum (Rio Abajo Spleenwort) · A. cristatum (Parsley Spleenwort) · A. cuneatum (Wedge-Leaf Spleenwort) · A. curtissii (Curtiss' Spleenwort) · A. dalhousiae (Countess Dalhousie's Spleenwort) · A. densum (Dense Spleenwort) · A. ebenoides (Dragon Tails Fern) · A. enatum (Queen Spleenwort) · A. esculentum (Vegetable Fern) · A. exiguum (Little Spleenwort) · A. feei (Fee's Spleenwort) · A. flabellifolium (Necklace Fern) · A. flabellulatum (Latin American Spleenwort) · A. flaccidum (Weeping Spleenwort) · A. flaccidum flaccidum (Weeping Spleenwort) · A. formosum (Showy Spleenwort) · A. goudeyi (Birds Nest Fern) · A. gravesii (Graves' Spleenwort) · A. haleakalense (Haleakala Spleenwort) · A. herb-wagneri (Herb's Spleenwort) · A. heterochroum (Bicolored Spleenwort) · A. heteroresiliens (Resilient Spleenwort) · A. hobdyi (Hobdy's Spleenwort) · A. horridum (Lacy Spleenwort) · A. inexpectatum (Spleenwort) · A. insiticium (Royal Spleenwort) · A. juglandifolium (Walnut Spleenwort) · A. kaulfussii (Kaulfuss Spleenwort) · A. kentuckiense (Kentucky Spleenwort) · A. laetum (Brownstem Spleenwort) · A. lobulatum (Piipiilau Manamana) · A. macraei (Macrae's Spleenwort) · A. monanthes (Single-Sorus Spleenwort) · A. montanum (Mountain Spleenwort) · A. morganii (Morgan's Spleenwort) · A. myriophyllum (Limestone Spleenwort) · A. neobrackenridgei (Neobrackenridge's Spleenwort) · A. nidus (Bird's Nest Fern) · A. nidus var. plicatum (Bird's Nest Fern) · A. nidus 'Antiquum' (Japanese Birds Nest) · A. nidus 'Osaka' (Osaka Bird's Nest Fern) · A. nidus 'Ruffled' (Ruffled Birds Nest Fern) · A. nodosum (Nodeless Danafern) · A. normale (Rainforest Spleenwort) · A. oblongifolium (Shining Spleenwort) · A. obtusatum (Shore Spleenwort) · A. obtusifolium (Bluntleaf Spleenwort) · A. ocoense (Rockledge Spleenwort) · A. palmeri (Palmer Spleenwort) · A. patens (Spreading Spleenwort) · A. pinnatifidum (Lobed Spleenwort) · A. platyneuron (Ebony Spleenwort) · A. platyneuron var. bacculum-rubrum (Ebony Spleenwort) · A. platyneuron var. platyneuron (Ebony Spleenwort) · A. platyneuron var. proliferum (Ebony Spleenwort) · A. plenum (Ruffled Spleenwort) · A. polyodon (Petako) · A. polyodon G.Forst. var. knudsenii (Hbd.) Morton (Knudsen's Birdnest Fern) · A. polyodon G.Forst. var. nitidulum (Skottsb.) Morton (Birdnest Fern) · A. polyodon G.Forst. var. sectum (Hbd.) Morton (Birdnest Fern) · A. polyodon G.Forst. var. subcaudatum (Skottsb.) Morton (Birdnest Fern) · A. polyodon var. knudsenii (Knudsen's Birdnest Fern) · A. polyodon var. nitidulum (Birdnest Fern) · A. polyodon var. sectum (Birdnest Fern) · A. polyodon var. subcaudatum (Birdnest Fern) · A. pseudoerectum (Antilles Spleenwort) · A. pteropus (West Indian Spleenwort) · A. pumilum (Dwarf Spleenwort) · A. radicans (Dullgreen Spleenwort) · A. resiliens (Black-Stem Spleenwort) · A. rhizophyllum (Walking Fern)

More Info

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Further Reading

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Notes

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Contributors

Identifiers

Footnotes

  1. Wagner, Warren H. Jr., Robbin C. Moran, and Charles R. Werth "Aspleniaceae". in Flora of North America Vol. 2. Oxford University Press. Online at EFloras.org. [back]
  2. Warren H. Wagner Jr., Robbin C. Moran, Charles R. Werth "Asplenium". in Flora of North America Vol. 2. Oxford University Press. Online at EFloras.org. [back]
  3. Gray, A. 2003. Asplenium ascensionis. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. <www.iucnredlist.org>. Downloaded on 30 January 2012. [back]
Last Revised: 7/22/2012