Leptosporangiate fern

Polypodiopsida/Pteridopsida ~ Modern Ferns
Tree fern
Scientific classification
Kingdom: Plantae
Division: Pteridophyta
Class: Polypodiopsida/Pteridopsida
(disputed)
Ritgen 1828
Orders

Leptosporangiate ferns are the largest group of living ferns, including some 11000 species worldwide.[1] They constitute the subclass Polypodiidae,[2][3] but are often considered to be the class Pteridopsida or Polypodiopsida,[4] although other classifications assign them a different rank.[5] The leptosporangiate ferns are one of the four major groups of ferns, with the other three being the Eusporangiate ferns comprising the marattioid ferns (Marattiidae, Marattiaceae), the horsetails (Equisetiidae, Equisetaceae), and whisk ferns and moonworts.[3][4]

There are approximately 8465 species of living leptosporangiate ferns, compared with about 2070 for all other ferns, totalling 10535 species of ferns.[2] Almost a third of leptosporangiate fern species are epiphytes.[6]

These ferns are called leptosporangiate because their sporangia arise from a single epidermal cell and not from a group of cells as in eusporangiate ferns (a polyphyletic lineage). The sporangia are typically covered with a scale called the indusium, which can cover the whole sorus, forming a ring or cup around the sorus, or can also be strongly reduced to completely absent. Many leptosporangiate ferns have an annulus around the sporangium, which ejects the spores.

Classification

Leptosporangiates include the vast majority of extant ferns. Only groups that branched off early from the fern lineage, which retain a eusporangium, are not included. Multiple attempts have been made to classify ferns. The classification scheme proposed by Smith et al. 2006 is the most widely accepted. More recent analyses by and Christenhusz et al. 2011 [3] and Christenhusz & Chase 2014 [2] offer additional insight into the group.

Phylogenic relationships

The following phylogram shows a likely relationship between the other vascular plant classes and the leptosporangiate ferns. It was formerly unclear about the relationship between Equisetopsida, Psilotopsida, and Marattiopsida,[8][9][10] but recent studies have shown that Equisetopsida is most likely sister to Psilotopsida.

Trachaeophyta

Lycopodiophytes (club mosses, spike mosses, quillworts)


Euphyllophytes

Spermatophytes (seed plants)


Ferns

Psilotopsida

 Psilotales (whisk ferns) 

 Ophioglossales (grapeferns etc.) 



Equisetopsida

 Equisetales (horsetails) 
Marattiopsida

 Marattiales 



Polypodiopsida

 Osmundales 

 Hymenophyllales (filmy ferns) 

 Gleicheniales 

 Schizaeales 

 Salviniales (heterosporous) 

 Cyatheales (tree ferns) 

 Polypodiales 

Discussion of Molecular Classification

There has been some challenge to recent molecular studies, claiming that these provide a skewed view of the phylogenetic order because they do not take into account fossil representatives.[11] However, the molecular studies have clarified relations among families that had already been thought to be polyphyletic before the advent of molecular information but that were left in their polyphyletic ranks because there was not enough information to do otherwise.[12] The classification of ferns using these molecular studies, which have generally supported one another, reflects the best information available at present, because traditional morphological characters are not always informative in elucidating evolutionary relationships among ferns [2]

References

  1. ↑ Palmer, Jeffrey (2004). "THE PLANT TREE OF LIFE: AN OVERVIEW AND SOME POINTS OF VIEW" (PDF). American Journal of Botany 91 (10): 1440. doi:10.3732/ajb.91.10.1437. PMID 21652302.
  2. 1 2 3 4 Christenhusz, M.J.M.; Chase, M.W. (2014). "Trends and concepts of fern classification". Annals of Botany 113 (4): 571–594. doi:10.1093/aob/mct299. Retrieved 17 July 2014.
  3. 1 2 3 4 5 Christenhusz, M.J.M., Zhang, X.C. & Schneider, H. (2011). "A linear sequence of extant families and genera of lycophytes and ferns" Phytotaxa 19: 5-22
  4. 1 2 Smith, A. R., K. M. Pryer, et al. (2006). "A classification for extant ferns." Taxon 55(3): 705-731
  5. ↑ Chase, Mark W. and Reveal, James L. (October 2009), "A phylogenetic classification of the land plants to accompany APG III", Botanical Journal of the Linnean Society 161 (2): 122–127, doi:10.1111/j.1095-8339.2009.01002.x
  6. ↑ Schuettpelz, Eric. "Fern Phylogeny Inferred from 400 Leptosporangiate Species and Three Plastid Genes," contained in "The Evolution and Diversification of Epiphytic Ferns." Doctoral dissertation, Duke University. 2007. http://dukespace.lib.duke.edu/dspace/bitstream/10161/181/1/D_Schuettpelz_Eric_a_052007.pdf
  7. ↑ Christenhusz, M.J.M. (2009). "New combinations and an overview of Cyathea subg. Hymenophyllopsis (Cyatheaceae)" Phytotaxa 1: 37-42
  8. ↑ Samuli Lehtonen (2011). "Towards Resolving the Complete Fern Tree of Life" (PDF). PLoS ONE 6 (10): e24851. doi:10.1371/journal.pone.0024851. PMC 3192703. PMID 22022365.
  9. ↑ Hardeep S. Rai & Sean W. Graham (2010). "Utility of a large, multigene plastid data set in inferring higher-order relationships in ferns and relatives (Monilophytes)" (PDF). American Journal of Botany 97 (9): 1444–1456. doi:10.3732/ajb.0900305.
  10. ↑ Kathleen M. Pryer & Eric Schuettpelz (2009). "Ferns" (PDF). In S. Blair Hedges & Sudhir Kumar. The Timetree of Life. Oxford Biology.
  11. ↑ Rothwell, G. W. and K. C. Nixon (2006). "How does the inclusion of fossil data change our conclusions about the phylogenetic history of euphyllophytes." Int. J. Plant Sci 167(3): 737-749
  12. ↑ Kramer, K. U. (1990). Notes on the Higher Level Classification of the Recent Ferns. The Families and Genera of Vascular Plants: Pteridophytes and Gymnosperms. K. Kubitzki, K. U. Kramer and P. S. Green. New York, Springer-Verlag. 1: 49-52

External links

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