Polystomellaceae Theiss. & P. Syd., Annls mycol. 13(3/4): 158 (1915).
MycoBank number: MB 81205; Index Fungorum: IF 81205; Facesoffungi number: FoF 06489, 43 species.
= Munkiellaceae (Theiss. & Syd.) Luttr., in Ainsworth et al., The fungi (London) 4a: 154 (1973).
Biotrophic or parasitic on leaves, typical tropical and subtropical distribution. Sexual morph: Stromata superficial or subcuticular, black, erumpent, pulvinate, and circular to suborbicular, elliptical or elongate, rugulose, containing mostly fungal tissue, globose to subglobose, uniloculate or multi- loculate (with 5 to numerous locules), hyphae flattened and ribbon-like with discrete central ostiole. Cells of ascostromata murky brown-walled textura angularis. Peridium of locules soft, often lightly pigmented thick-walled cells of textura angularis and in side view pseudoparenchymatous, darken above locules. Hamathecium comprising numerous, hyaline, septate or aseptate cellular pseudoparaphyses without branching, often deliquescent at maturity. Asci 8-spored, bitunicate, fissitunicate, relatively short, oblong to cylindro-clavate or occasionally obclavate, often ventricose, with a short pedicel, apically rounded, with a small ocular chamber. Ascospores 1–2-seriate, fusiform to ellipsoidal or obpyriform, hyaline, yellowish to olive brown, 0–1-septate, upper cell wider and shorter than the lower cell, euseptate, septate near the lower end or middle, with or without constrictions at the septum, asymmetric, lacking a sheath, wall smooth or verruculose with guttulate contents, sometimes crowded in ascus. Asexual morph: Coelomycetous, acervular, linked to Lasmenia and Stictochorella (Wakefield 1940; Swart 1987; Kirk et al. 2008); conidiogenesis often holoblastic.
Type: Dothidella Speg.
Notes: Polystomellaceae was introduced by Theissen and Sydow (1915) for Munkiella, Parmularia and Polystomella (the type genus) based upon a foot or hypostroma which anchors the thyrothecium within the host (von Arx and Müller 1975). Other names used for this family are Stigmateaceae (Theissen 1916) and Munkiellaceae (Luttrell 1973). Polystomellaceae consists of species with superficial ascomata, while in Munkiellaceae ascomata are subcuticular, yet the two families were combined by Eriksson (1981). Barr (1987a) included Polystomellaceae as a family in Pleosporales with the genera Atopospora, Hormotheca (currently referred to Venturiaceae) and Ellisiodothis (currently referred to Microthyriaceae). Lumbsch and Huhndorf (2010) included three genera Dothidella (= Polystomella) with ascospores having a median septum, Munkiella with apiospores and Parastigmatea in Polystomellaceae under Dothideomycetes, family incertae sedis, and this was followed by Index Fungorum (2020). All share similar characteristics such as a stromatic ascomata resulting from ascolocular ontogeny, with uni- to multi-locular ascostromata, and hyaline ascospores, with one or two cells. Several other genera with amerospores and two with phragmospores have been included in Munkiellaceae (Luttrell 1973). von Arx and Müller (1954) placed Parastigmatea under Botryosphaeriaceae, while in a recent review of the family, Liu et al. (2012) did not include the genus in this family. The three genera placed in Polystomellaceae were described before 1965 (Index Fungorum 2020) and no molecular sequence data is available. Thus, fresh collections are needed to establish the phylogenetic relationships of the genera and Polystomellaceae. Munkiella and Parastigmatea are presently listed in Polystomellaceae, but their inclusion is uncertain for the purpose of keying out the genera.