Vittarioideae

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.Schuettpelz ''et al.'' (2007)
Eric Schuettpelz, Harald Schneider, Layne Huiet, Michael D. Windham, Kathleen M. Pryer: "A molecular phylogeny of the fern family Pteridaceae: Assessing overall relationships and the affinities of previously unsampled genera." ''Molecular Phylogenetics and Evolution'' 44 (2007) 1172–1185

History

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 grammitid ferns. He invented the new genus ''Haplopteris'' to accommodate another group of simple-leaved ferns separated from ''Pteris'', but placed it in tribe Adiantaceae instead, due to the location of its sori just behind the leaf margin.

In his 1911 treatment of the tribe, Ralph Benedict adopted a circumscription similar to modern treatments, within which he recognized the genera ''Ananthacorus'', ''Anetium'', '' Antrophyum'', '' Hecistopteris'', '' Monogramma'', '' Polytaenium'', and ''Vittaria''. He described '' Radiovittaria'' as a subgenus of ''Vittaria'', subsumed '' Scoliosorus'' within '' Polytaenium'' as doubtfully worthy of subgeneric rank, while '' Rheopteris'' had not yet been discovered. ''Haplopteris'' he explicitly synonymized with ''Vittaria'' in 1914.

Carl Christensen used the name "Vittarioideae" in Verdoorn's ''Manual of Pteridology'' in 1938, but did not include a description, leaving it nomenclaturally invalid. Ren-Chang Ching raised Vittariaceae to the rank of a family in 1940.

The first well-sampled molecular phylogenetic study of the vittarioids was based on the chloroplast gene rbcL. In this study, it was found that the type species of ''Monogramma'' is embedded in ''Haplopteris''; the segregation of '' Vaginularia'' from ''Monogramma'' was also supported, as members of ''Vaginularia'' formed a clade sister to ''Rheopteris'' and distant from ''Monogramma'' ''sensu stricto''.Bradley Ruhfel, Stuart Lindsay, and Charles C. Davis. 2008. "Phylogenetic Placement of ''Rheopteris'' and the Polyphyly of ''Monogramma'' (Pteridaceae s.l.): Evidence from rbcL Sequence Data". ''Systematic Botany'' 33(1):37-43, A later molecular phylogeny, published in 2016, established the genus '' Antrophyopsis'' (formerly a subgenus of ''Antrophyum'') for three species placed in ''Scoliosorus'' but more distant from the type of that genus than ''Antrophyum''. This treatment also sank ''Anetium'' into ''Polytaenium'' and ''Monogramma'' into ''Haplopteris''. Since the name ''Monogramma'' has taxonomic priority over ''Haplopteris'', a proposal to reject ''Monogramma'' in favor of ''Haplopteris'' has been put forth to conserve the name and comparatively stable circumscription of ''Haplopteris''.

Genera

The following genera are recognized in the Pteridophyte Phylogeny Group classification of 2016 (PPG I):
*''Adiantum'' L.
*''Ananthacorus'' Underw. & Maxon
*'' Antrophyopsis'' (Benedict) Schuettp.
*'' Antrophyum'' Kaulf.
*''Haplopteris'' C.Presl
*'' Hecistopteris'' J.Sm.
*'' Polytaenium'' Desv.
*'' Radiovittaria'' (Benedict) E.H.Crane
*'' Rheopteris'' Alston
*'' Scoliosorus'' T.Moore
*'' Vaginularia'' Fée
*''Vittaria'' Sm.

The following phylogeny for the currently recognized genera of the subfamily was presented by Schuettpelz ''et al.'':

References

{{Taxonbar, from1=Q5873935, from2=Q19387804, from3=Q3735428

Pteridaceae
Plant subfamilies