Vittarioideae is a subfamily of the fern family Pteridaceae, in the order Polypodiales. The subfamily includes the previous families Adiantaceae (adiantoids or maidenhair ferns) and Vittariaceae (vittarioids or shoestring ferns).
Description
The subfamily includes two distinct groups of ferns: the adiantoids, consisting of the single genus Adiantum, and the vittarioids, several genera, including Vittaria, which typically have highly reduced leaves, usually entire, and an epiphytic habit. The ferns historically considered as Adiantum include both petrophilic and terrestrial plants. The vittarioid ferns are primarily epiphytic in tropical regions and all have simple leaves with sori that follow the veins and lack true indusia; the sori are most often marginal with a false indusium formed from the reflexed leaf margin. The family also includes a species, Vittaria appalachiana, that is highly unusual in that the sporophyte stage of the life cycle is absent. This species consists solely of photosynthetic gametophytes that reproduce asexually.
Taxonomy
Molecular phylogenetic analysis demonstrated that the vittarioid ferns were nested within the genus Adiantum as it was originally circumscribed, making that genus paraphyletic. In the Pteridophyte Phylogeny Group classification of 2016 (PPG I), the family is treated as the subfamily Vittarioideae] of the family Pteridaceae.
The following diagram shows a likely phylogenetic relationship between the Vittarioideae and other subfamilies of the Pteridaceae.
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Pteridaceae
Cryptogrammoideae
Parkerioideae (syn. Ceratopteridoideae)
Pteridoideae
Cheilanthoideae
Vittarioideae
The first suprageneric classification based on Vittaria was made by Carl Borivoj Presl in 1836, who erected the tribe Vittariaceae to contain the genera Vittaria and Prosaptia, the latter now included in the...
