Aspleniaceae

Common name:         unknown  

Conservation status: unkown

Etymology:   

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Spores:                            

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Leaves:         

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Stem & branches: 

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Roots:         

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Habit:        

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Habitat:   

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Distribution:                  

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Species:                     

• World:            S,    G

• Australia:      S,    G

Additional notes:     

• The Aspleniaceae (spleenworts) are a family of ferns, included in the order Polypodiales

• The composition and classification of the family have been subject to considerable changes

• In particular, there is a narrow circumscription, Aspleniaceae s.s. (adopted here), in which the family contains only two genera, and a very broad one, Aspleniaceae s.l., in which the family includes 10 other families kept separate in the narrow circumscription, with the Aspleniaceae s.s. being reduced to the subfamily Asplenioideae

• The family has a worldwide distribution, with many species in both temperate and tropical areas

• Elongated unpaired sori are an important characteristic of most members of the family.

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• Description

  • Members of the family grow from rhizomes, that are either creeping or somewhat erect, and are usually but not always unbranched, and have scales that usually have a lattice-like (clathrate) structure

  • In some species, for example Asplenium nidus, the rhizomes form a kind of basket which collects detritus

  • The leaves may be undivided or be divided, with up to four-fold pinnation

  • The sori are characteristic of the family

    • They are elongated, and normally located on one side of a vein

    • More rarely, they may be in pairs on a single vein, but then they never curve over the vein

    • A flap-like indusium arises along one edge of a sorus

  • The leaf stalks (petioles) have two vascular bundles, uniting to form an X-shape in cross-section towards the tip of the leaf

  • The stalks of the sporangia are one cell wide in the middle

• Taxonomy

  • The family Aspleniaceae was first described by Edward Newman in 1840

  • Newman included three genera: Athyrium, Asplenium and Scolopendrium

  • Athyrium is now placed in a different family, Athyriaceae, not considered very strongly related to the Aspleniaceae, and Scolopendrium is regarded as synonym of Asplenium

  • The narrow circumscription of the family adopted by the Pteridophyte Phylogeny Group classification of 2016 (PPG I) recognizes only two genera

  • Asplenium and Hymenasplenium. Asplenium has previously been split into a dozen or so genera, including Diella, found only in Hawaii

  • The consensus of molecular phylogenetic studies is that all are nested within Asplenium

  • PPG I places Aspleniaceae in the suborder Aspleniineae of the order Polypodiales

  • Earlier, Christenhusz and Chase had proposed a much broader circumscription of Aspleniaceae, in which it consisted of all the separate families that PPG I places in the suborder Aspleniineae (eight at the time), with the families reduced to subfamilies

  • Thus the Aspleniaceae of PPG I became the subfamily Asplenioideae

  • As of July 2019, the broader circumscription of the Aspleniaceae is used by Plants of the World Online, which lists 24 genera

• Phylogenic relationships

  • Aspleniaceae is placed in a clade known as eupolypods II, or more formally as suborder Aspleniineae

  • The following cladogram, based on Lehtonen (2011) and Rothfels & al. (2012) shows a likely phylogenic relationship between the Aspleniaceae and the other families in the clade