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Selaginella

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Spikemoss
Temporal range: Late Carboniferous–Recent
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Lycophytes
Class: Lycopodiopsida
Order: Selaginellales
Prantl
Family: Selaginellaceae
Willk.
Genus: Selaginella
P. Beauv.
Type species
Selaginella selaginoides
Species

See text.

Synonyms
  • Bryodesma Soják 1992
  • Carpolepidium Palisot de Beauvois 1805
  • Didiclis Palisot de Beauvois 1803
  • Diplostachyum Palisot de Beauvois 1805
  • Gymnogynum Palisot de Beauvois 1804
  • Heterophyllae Spring 1840
  • Heterophyllium Hieronymus ex Börner 1912
  • Homoeophyllae Spring 1840
  • Homostachys Warburg 1900
  • Hypopterygiopsis Sakurai 1943
  • Lycopodioides Boehm. 1760 ex Kuntze 1891
  • Mirmau Adanson 1763
  • Polycocca Hill 1773 nom. superfl.
  • Selaginoides Séguier 1754 nom. rej.
  • Selago Browne 1756 nom. ill.
  • Stachygynandrum Palisot de Beauvois 1804 nom. rej.
  • Trispermium Hill 1773
Curled up Selaginella tamariscina
Wallace's Selaginella (Selaginella wallacei)

Selaginella, also known as spikemosses or lesser clubmosses is a genus of lycophyte. It is usually treated as the only genus in the family Selaginellaceae, with over 750 known species.

This family is distinguished from Lycopodiaceae (the clubmosses) by having scale-leaves bearing a ligule and by having spores of two types. They are sometimes included in an informal paraphyletic group called the "fern allies". The species S. moellendorffii is an important model organism. Its genome has been sequenced by the United States Department of Energy's Joint Genome Institute.[1] The name Selaginella was erected by Palisot de Beauvois solely for the species Selaginella selaginoides, which turns out (with the closely related Selaginella deflexa) to be a clade that is sister to all other Selaginellas, so any definitive subdivision of the species into separate genera leaves two taxa in Selaginella, with the hundreds of other species in new or resurrected genera.

Selaginella occurs mostly in the tropical regions of the world, with a handful of species to be found in the arctic-alpine zones of both hemispheres.[2] Fossils assignable to the modern genus are known spanning over 300 million years from the Late Carboniferous to the present.[3]

Description

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Selaginella species are creeping or ascendant plants with simple, scale-like leaves (microphylls) on branching stems from which roots also arise. The stems are aerial, horizontally creeping on the substratum (as in Selaginella kraussiana), sub-erect (Selaginella trachyphylla) or erect (as in Selaginella erythropus). The vascular steles are polystelic protosteles. Stem section shows the presence of more than two protosteles. Each stele is made up of diarch (having two strands of xylem[4]) and exarch (growing outward in) xylems.[citation needed] The steles are connected with the cortex by means of many tube-like structures called trabeculae, which are modified endodermal cells with casparian strips on their lateral walls.[citation needed] The stems contain no pith.[citation needed]

In Selaginella, each microphyll and sporophyll has a small scale-like outgrowth called a ligule at the base of the upper surface.[5]: 7  The plants are heterosporous with spores of two different size classes, known as megaspores and microspores.[6]

Unusual for the lycopods, which nearly always have microphylls with a single unbranched vein, the microphylls of a few Selaginella species contain a branched vascular trace.[7]

Under dry conditions, some species of Selaginella can survive dehydration. In this state, they may roll up into brown balls and be uprooted, but can rehydrate under moist conditions, become green again and resume growth. This phenomenon is known as poikilohydry, and poikilohydric plants such as Selaginella bryopteris are sometimes referred to as resurrection plants.[8]

There is no evidence of whole genome duplication in Selaginella's evolutionary history. Instead they have gone through tandem gene duplications, which is particularly noticeable in genes relevant for desiccation tolerance.[9][jargon]

Taxonomy

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Some scientists still place the Selaginellales in the class Lycopodiopsida (often misconstructed as "Lycopsida").[citation needed][10][11] Some modern authors recognize three generic divisions of Selaginella: Selaginella, Bryodesma Sojak 1992, and Lycopodioides Boehm 1760. Lycopodioides would include the North American species S. apoda and S. eclipes, while Bryodesma would include S. rupestris (as Bryodesma rupestre). Stachygynandrum is also sometimes used to include the bulk of species.[citation needed]

The first major attempt to define and subdivide the group was by Palisot de Beauvois[12] in 1803–1805. He established the genus Selaginella as a monotypic genus, and placed the bulk of species in Stachygynandrum. Gymnogynum was another monotypic genus, but that name is superseded by his own earlier name of Didiclis. This turns out, today, to be a group of around 45–50 species also known as the Articulatae, since his genus Didiclis/Gymnogynum was based on Selaginella plumosa. He also described the genus Diplostachyum to include a group of species similar to Selaginella apoda. Spring inflated the genus Selaginella to hold all selaginelloid species four decades later.

Phylogenetic studies by Korall & Kenrick[13][14] determined that the Euselaginella group, comprising solely the type species, Selaginella selaginoides and a closely related Hawaiian species, Selaginella deflexa, is a basal and anciently diverging sister to all other Selaginella species. Beyond this, their study split the remainder of species into two broad groups, one including the Bryodesma species, the Articulatae, section Ericetorum Jermy and others, and the other centered on the broad Stachygynandrum group.

In 2023, Zhou & Zhang suggested that the genus should be broken up into 19 different genera.[15]

Walton & Aston 1938[16] Weststrand & Korall 2016 [17]
  • subgenus: Euselaginella
    • group: selaginoides
    • group: pygmaea
    • group: uliginosa (Ericetorum)
    • group: rupestris (Tetragonostachys or Bryodesma)
  • subgenus: Stachygynandrum
    • series: Decumbentes
    • series: Ascendentes
    • series: Sarmentosae
    • series: Caulescentes
    • series: Circinatae
    • series: Articulatae
  • subgenus: Homostachys
  • subgenus: Heterostachys
  • subgenus: Selaginella
  • clade: "Rhizophoric clade"
    • clade A
      • subgenus Rupestrae [Bryodesma Sojak or Tetragonostachys Jermy, S. section Homeophyllae]
      • subgenus Lepidophyllae [S. section Lepidophyllae]
      • subgenus Gymnogynum [S. section Articulatae]
      • subgenus Exaltatae [incl. S. section Megalosporum, S. section Myosurus]
      • subgenus Ericetorum [S. section Lyallia]
    • clade B
      • subgenus Stachygynandrum [incl. S. (Boreoselaginella), S. (Pulviniella), S. (Heterostachys)]

Zhang & Zhou, 2015 classification

[edit]

[18]

  • subgenus: Selaginella Type: S. selaginoides (L.) P.Beauv. ex Mart. & Schrank
  • subgenus: Boreoselaginella Type: S. sanguinolenta (L.) Spring
  • subgenus: Ericetorum Type: S. uliginosa (Labill.) Spring
    • section: Lyallia Type: S. uliginosa (Labill.) Spring
    • section: Myosurus Type: S. myosurus Alston
    • section: Megalosporarum Type: S. exaltata (Kunze) Spring
    • section: Articulatae Type: S. kraussiana (Kunze) A.Braun
    • section: Homoeophyllae Type: S. rupestris (L.) Spring (=Bryodesma Sojak or Tetragonostachys Jermy)
    • section: Lepidophyllae Type: S. lepidophylla (Hook. & Grev.) Spring
  • subgenus: Pulviniella Type: S. pulvinata (Hook. & Grev.) Maxim
  • subgenus: Heterostachys Type: S. heterostachys Baker
    • section: Oligomacrosporangiatae Type: Selaginella uncinata (Desv. ex Poir.) Spring
    • section: Auriculatae Type: S. douglasii (Hook. & Grev.) Spring
    • section: Homostachys Type: : S. helvetica (L.) Link
    • section: Tetragonostachyae Type: S. proniflora (L.) Baker
    • section: Heterostachys Type: S. brachystachya (Hook. & Grev.) Spring
  • subgenus: Stachygynandrum Type: S. flabellata (L.) Spring
    • section: Plagiophyllae Type: S. biformis A.Braun ex Kuhn
    • section: Circinatae Type: S. involvens (Sw.) Spring
    • section: Heterophyllae Type: S. flexuosa Spring
    • section: Austroamericanae Type: S. hartwegiana Spring
    • section: Pallescentes Type: S. pallescens (C.Presl) Spring
    • section: Proceres Type: S. oaxacana Spring
    • section: Ascendentes Type: S. alopecuroides Baker
Zhang & Zhou 2015[18] Zhou & Zhang 2023[15]
Selaginella

subgenus Selaginella

subgenus Boreoselaginella

subgenus

section Megalosporum

section Myosurus

section Lyallia

section Articulatae

section Lepidophyllae

section Homeophyllae

Gymnogynum

subgenus Pulviniella

subgenus

section Tetragonostachyae

section Heterostachys

section Auriculatae

section Homostachys

section

S. braunii subclade

S. willdenowii subclade

S. pennata subclade

S. pervillei subclade

S. siamensis subclade

S. delicatula subclade

Oligomacrosporangiatae
Heterostachys
subgenus

section Plagiophyllae

section Circinatae

section Ascendentes

section Proceres

section Pallescentes

section Austroamericanae

section Heterophyllae

Stachygynandrum
Selaginellaceae
Selaginoidoideae

Selaginoides Séguier 1754

Boreoselaginelloideae

Boreoselaginella (Warburg 1900) Zhang & Zhou 2023

Gymnogynoideae

Afroselaginella Zhang & Zhou 2023

Megaloselaginella Zhang & Zhou 2023

Ericetorum (Jermy 1986) Zhang & Zhou 2023

Gymnogynum Palisot de Beauvois 1804

Lepidoselaginella Zhang & Zhou 2023

Bryodesma Soják 1992

Pulvinielloideae

Pulviniella (Zhang & Zhou 2015) Zhang & Zhou 2023

Sinoselaginelloideae

Sinoselaginella Zhang & Zhou 2023

Austroselaginella Zhang & Zhou 2023

Korallia Zhang & Zhou 2023

Lycopodioidoideae

Valdespinoa Zhang & Zhou 2023

Lycopodioides Boehm. 1760 ex Kuntze 1891

Didiclis Palisot de Beauvois ex Mirb. 1802

Hypopterygiopsis Sakurai 1943

Selaginelloideae

Chuselaginella Zhang & Zhou 2023

Kungiselaginella Zhang & Zhou 2023

Selaginella

section Proceres Spring 1850

section Pallescentes Zhang & Zhou 2015

section Austroamericanae Zhang & Zhou 2015

section Heterophyllae Spring 1840

Species

[edit]
Main article: List of Selaginella species
Selaginella selaginoides
Selaginella willdenowii is known for its iridescent colours

There are about 750 known species of Selaginella.[19] They show a wide range of characters; the genus is overdue for a revision which might include subdivision into several genera.[citation needed] Species of spikemoss include:

A few species of Selaginella are desert plants known as "resurrection plants", because they curl up in a tight, brown or reddish ball during dry times, and uncurl and turn green in the presence of moisture. Other species are tropical forest plants that appear at first glance to be ferns.

Cultivation

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A number of Selaginella species are popular plants for cultivation, mostly tropical species. Some of the species popularly cultivated and actively available commercially include:

  • S. kraussiana: golden clubmoss
  • S. martensii: frosty fern
  • S. moellendorffii: gemmiferous spikemoss
  • S. erythropus: red selaginella or ruby-red spikemoss
  • S. uncinata: peacock moss
  • S. lepidophylla: resurrection plant
  • S. braunii: arborvitae fern

References

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  1. ^ "Selaginella moellendorffii v1.0". Joint Genome Institute. United States Department of Energy. 2007. Retrieved 2009-04-08.
  2. ^ "Selaginella kraussiana | PlantZAfrica".
  3. ^ Bek, Jiří; Libertín, Milan; Drábková, Jana (June 2009). "Selaginella labutae sp. nov., a new compression herbaceous lycopsid and its spores from the Kladno–Rakovník Basin, Bolsovian of the Czech Republic". Review of Palaeobotany and Palynology. 155 (3–4): 101–115. Bibcode:2009RPaPa.155..101B. doi:10.1016/j.revpalbo.2007.12.010.
  4. ^ "Diarch". The Free Dictionary.
  5. ^ Stace, C. A. (2010). New Flora of the British Isles (Third ed.). Cambridge, U.K.: Cambridge University Press. ISBN 9780521707725.
  6. ^ Petersen, Kurt B.; Burd, Martin (2018). "The adaptive value of heterospory: Evidence from Selaginella". Evolution. 72 (5): 1080–1091. doi:10.1111/evo.13484. ISSN 1558-5646. PMID 29645092. S2CID 4800398.
  7. ^ Wagner, Warren H.; Beitel, Joseph M.; Wagner, Florence S. (1982-11-19). "Complex Venation Patterns in the Leaves of Selaginella : Megaphyll-Like Leaves in Lycophytes". Science. 218 (4574): 793–794. Bibcode:1982Sci...218..793W. doi:10.1126/science.218.4574.793. ISSN 0036-8075. PMID 17771037. S2CID 44904740.
  8. ^ Liberty Hyde Bailey (1916). The Standard Cyclopedia of Horticulture. Vol. 5. The Macmillan company. pp. 2920–2921, 3639.
  9. ^ VanBuren, Robert; Ching, Man Wai; Ou, Shujun; Pardo, Jeremy; Bryant, Doug; Jiang, Ning; Mockler, Todd C.; Edger, Patrick; Michael, Todd P. (2018). "Extreme haplotype variation in the desiccation- tolerant clubmoss Selaginella lepidophylla". Nature Communications. 9 (13): 13. Bibcode:2018NatCo...9...13V. doi:10.1038/s41467-017-02546-5. PMC 5750206. PMID 29296019.
  10. ^ Clugston, M. (2014). Dictionary of Science (4th ed.). London: Penguin Reference Library. p. 743. ISBN 978-0-141-98682-1.
  11. ^ Walker, Peter (1992). Chambers Science and Technology Dictionary (4th ed.). Edinburgh NewYork: Chambers. p. 999. ISBN 0-550-13239-2.
  12. ^ Palisot de Beauvois (1805): Prodrome des cinquième et sixième familles de l'Æthéogamie, les mousses, les lycopodes.
  13. ^ Korall, P. & Kenrick, P. (2002), "Phylogenetic relationships in Selaginellaceae based on rbcL sequences", American Journal of Botany, 89 (3): 506–17, doi:10.3732/ajb.89.3.506, PMID 21665649
  14. ^ Korall & Kenrick (2004): The phylogenetic history of Selaginellaceae based on DNA sequences from the plastid and nucleus: extreme substitution rates and rate heterogeneity. Molecular Phylogenetics and Evolution, Volume 31, Issue 3, June 2004, Pages 852–864
  15. ^ a b Zhou, Xin-Mao; Zhang, Li-Bing (2023), "Phylogeny, character evolution, and classification of Selaginellaceae (lycophytes)", Plant Diversity, 45 (6): 630–684, Bibcode:2023PlDiv..45..630Z, doi:10.1016/j.pld.2023.07.003, PMC 10772194, PMID 38197007
  16. ^ Verdoorn, F., ed. (1938): Manual of Pteridology: J. Walton and A. H. G. Alston, Lycopodinae, pp. 500–506. Martinus Nijhoff, The Hague. 640pp, HB.
  17. ^ Weststrand, Stina; Korall, Petra (2016), "A subgeneric classification of Selaginella (Selaginellaceae)", American Journal of Botany, 103 (12): 2160–2169, doi:10.3732/ajb.1600288, PMID 27999080
  18. ^ a b Zhou, Xin-Mao; Zhang, Li-Bing (2015), "A classification of Selaginella (Selaginellaceae) based on molecular (chloroplast and nuclear), macromorphological, and spore features", Taxon, 64 (6): 1117–1140, doi:10.12705/646.2, S2CID 90451945
  19. ^ Christenhusz, M. J. M. & Byng, J. W. (2016). "The number of known plants species in the world and its annual increase". Phytotaxa. 261 (3): 201–217. doi:10.11646/phytotaxa.261.3.1.
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