Microgramma C.Presl, Tent. Pterid.

Smith, Alan R., Kessler, Michael, León, Blanca, Almeida, Thaís Elias, Jiménez-Pérez, Iván & Lehnert, Marcus, 2018, Prodromus of a fern flora for Bolivia. XL. Polypodiaceae, Phytotaxa 354 (1), pp. 448-450 : 448-450

Microgramma C.Presl, Tent. Pterid. 213. 1836.

= Solanopteris Copel., Amer. Fern J. 41(3): 75, 128. 1951.

Microgramma is a segregate from Polypodium s.l. and is characterized by monomorphic to dimorphic fronds, reticulate veins, peltately attached non-clathrate rhizome scales, and uniseriate sori with paraphyses of narrow scales or hairlike structures. Dimorphism and venation in the genus were discussed by de la Sota & Pérez-Garcia (1982). Molecular data suggest exclusion of Polypodium chrysolepis from Microgramma , where it has often been placed ( Schneider et al. 2004); it is here included in the genus Adetogramma ( Almeida et al. 2017) . Microgramma is a genus of about 30 species, mostly in the Neotropics, but with one species in Africa and offshore islands; 16 species are known from Bolivia. This treatment is based on studies developed as part of the author’s thesis ( Almeida 2014), preparatory to a monograph (Almeida et al. in prep.)

Characters used to distinguish species of Bolivian Microgramma include: rhizomes (whether round in cross-section or flattened); rhizome scale margin (entire, erose, ciliate or toothed) and color (concolorous vs. sharply bicolored); leaf dimorphism (vs. monomorphism); blade indument (lacking vs. scaly) and texture (chartaceous or coriaceous); soral indument (lacking, abundant basally branched filamentous trichomes, or scales).

The genus Solanopteris , which has been recognized by some authors (e.g., Tryon & Tryon 1982; Tryon & Stolze 1993), has been shown from molecular data to nest within Microgramma ( Schneider et al. 2004, Salino et al. 2008, Almeida in prep.). The species previously recognized in Solanopteris differ from other Microgramma species by bearing swollen, hollow tubers along the rhizomes that are usually inhabited by ants ( Rauh 1955, Tryon & Stolze 1993). Spores of this subclade also have a long-spiny perispore ( Tryon & Stolze 1993), a unique character in Polypodiaceae , and presumably an adaptation related to the co-evolutionary relationship with ants ( Hennipman 1990).