Karschia
Karschia Körb., Parerga lichenol. (Breslau) 5: 459 (1865).
Index Fungorum number: IF 2545; Facesoffungi number: FoF 07619, 24 morphological species (Species Fungorum 2022), 2 species with molecular data.
Lichenicolous or non-lichenized. Sexual morph: Ascomata apothecioid pseudothecia, black, erumpent, round, with prominent rough margin, with a disc that becomes exposed by crumbling of the obtecting parts of the ascomatal wall. Exciple pseudoparenchymatic, composed of cells with dark brown walls. Hymenium hyaline, distinct, with 1- (or giving a faintly blue reaction with 1 after pretreatment with K) hymenial gel. Hamathecium present as paraphysoids. Paraphysoids branching and with anastomoses, showing even in mature ascomata some connections with remnants of the ascomatal wall overlaying the epihyrnenium, Hypothecium pale to dark brown. Asci broadly cylindrical to slightly ventricose, fissitunicate, with an apically enlarged endoascal wall layer. Ascospores brown, one-septate, with constantly narrower lower cell, with solid wall but without germinating pores. Asexual morph: Conidiomata not observed (adapted from Hafellner 2004).
Type species: Karschia talcophila (Ach.) Körb.
Notes: Karschia is characterised by apothecioid pseudothecia, pseudoparenchymatic exciple, hyaline, distinct hymenium, paraphysoids hamathecium, pale to dark brown hypothecium and brown, one-septate ascospores. Karschia was used for lichenicolous discomycetes characterised by brown, one-septate ascospores. Hafellner and Poelt (1976) reported that Karschia is heterogeneous based on investigations of the hymenial characters of the taxa. Clements (1909) introduced Epilichen for parasitic taxa previously placed in Karschia and members with definite or evanescent thallus have been transferred to Buellia (Butler 1940). Hafellner (1979) transferred several Karschia species to Colensoniella, Heterosphaeriopsis, Rhizodiscina, Schrakia (Dothideales) and Stratisporella and accepted only K. talcophila and K. santessonii in Karschia. Hawksworth et al. (1995) and Courtecuisse et al. (1996) listed Karschia in Dothideales genera incertae sedis. Kirk et al. (2008) and Lumbsch and Huhndorf (2010) mentioned Karschia in Dothideales genera incertae sedis. Karschia resembles members of Lichenotheliaceae in having lichenicolous, episubstratic or endokapylic, areolate thallus, fertile stromata of several shapes, without an ostiole, globose to broadly clavate asci and hyaline to brown, uniseptate ascospores (Hyde et al. 2013, Thambugala et al. 2014). Thambugala et al. (2014) re-examined the holotype specimen K. talcophila (S-F203801) and tentatively placed the genus in Lichenotheliaceae. Ertz and Diederich (2015) re-studied the type specimen of Karschia and provided sequence data. In the phylogenetic analysis of Ertz and Diederich (2015) based on nuLSU and mtSSU, Karschia formed a distinct lineage close to Labrocarpon, Melaspileopsis and Stictographa. Dai et al. (2018) reported the same result as Ertz and Diederich (2015) and placed Karschia in Stictographaceae based on phylogenetic evidence of LSU and SSU genes. Karschia is morphologically and phylogenetically a distinct genus in Stictographaceae. Only LSU sequence data is available for two species, K. cezannei and K. talcophila. More collections with sequence data and more gene regions are needed to verify this placement.
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