Buelliella Fink, Lich. Fl. U.S.: 372 (1935).
Non-lichenized or lichenicolous. Sexual morph: Apothecioid roundish, more or less superficial, ascomata that are initially subspherical and closed, with the upper ascomatal wall opening irregularly in the center and breaking gradually away to expose the hymenium when mature. Exciple medium to dark brown, K– (in B. trypethelii purplish, K+ aeruginose) exciple. Hymenium that is K/I– or pale blue; linear, sometimes branched or anastomosed paraphyses, that may be apically slightly enlarged and brownish. Periphyses short, few-celled arising from the inner excipular layer. Asci bitunicate, broadly clavate to subcylindrical, mostly 8-spored, wall apically thickened, with a distinct ocular chamber, I– and K/I–. Ascospores ellipsoid, 1-septate, smooth, pale to medium brown ascospores that are slightly constricted near the septum (Adapted from Ertz et al. 2015).
Type species: Buelliella minimula (Tuck.) Fink
Notes: Buelliella was introduced by Fink (1935) with B. minimula as type species. Buelliella is characterised by roundish, more or less superficial, ascomata, medium to dark brown exciple, broadly clavate to subcylindrical 8-spored asci and ellipsoid, 1-septate, smooth, pale to medium brown ascospores. Hafellner (1979) validated the diagnosis of Fink (1935). Ertz and Diederich (2015) reported that Buelliella is not monophyletic as B. physciicola and B. poetschii are distantly related and the type species B. minimula lacked sequence data. Kirk et al. (2008), Ertz and Diederich (2015) and Wijayawardene et al. (2017) placed Buelliella in Dothideomycetes genera incertae sedis. Hongsanan et al. (2020b) included LSU sequence data of B. minimula in their phylogenetic analysis and reported that the latter formed a distinct lineage within Sticgraphaceae. Hongsanan et al. (2020b) also synonymized and transferred Buelliella poetschii to another genus Neobuelliella. Buelliella is morphologically and phylogenetically a distinct genus in Stictographaceae but it seems to be a heterogeneous genus as only a small number of species have sequence data and the generic type lack molecular data. Molecular markers available for Buelliella include LSU of Buelliella minimula, B. physciicola and B. poetschii.