(2953) Proposal to conserve the name Absconditella against Geisleria (Ascomycota: Lecanoromycetes)

Abstract

(2953) Absconditella Vězda in Preslia 37: 238. 1965, nom. cons. prop. Typus: A. sphagnorum Vězda & Poelt (=) Geisleria Nitschke in Rabenhorst, Lich. Eur. Exs. No. 574. Oct 1861, nom. rej. prop. Typus: G. sychnogonioides Nitschke Vězda (in Preslia 37: 238. 1965) introduced a new genus of lichenized fungi, Absconditella (Stictidaceae, Ostropales, Lecanoromycetes, Ascomycota) with A. sphagnorum Vězda & Poelt as the type to accommodate species having minute, urceolate (apothecioid) ascomata with a non-amyloid hymenium and without a dark pigment, simple and indistinctly septate paraphyses, asci with a distinct non-amyloid tholus and chlorococcoid algae as a photobiont. At least 12 additional species have been described (Vězda, l.c. 1965; Vězda & Vivant in Folia Geobot. Phytotax. 10: 205. 1975; Döbbeler & Poelt in Herzogia 4: 364. 1977; Vězda & Pišút in Nova Hedwigia 40: 342, 344. 1985 [“1984”]; Søchting & al. in Biblioth. Lichenol. 88: 613. 2004; Spribille & al. in Bryologist 112: 111. 2009; Kondratyuk & al. in Acta Bot. Hung. 55: 277. 2013; Van den Boom & al. in Phytotaxa 238: 272. 2015; Cáceres & Aptroot in Bryologist 119: 254. 2016; Kalb & Aptroot in Bryologist 121: 57, 60. 2018) and four have been transferred from other genera (Vězda, l.c. 1965: 241, 244; Rossman in Mycotaxon 8: 505. 1979; Hawksworth & al. in Lichenologist 12: 106. 1980). The genus is cosmopolitan, and most species are sporadically collected due to their small size and probably ephemeral nature. The name Geisleria was introduced by Nitschke (in Rabenhorst, Lich. Eur. Exs. No. 574. 1861) for a single species, G. sychnogonioides Nitschke. Three more species were described later, one of which, G. alpina Servít (in Blumea 7: 594. 1954), appeared to be a parasymbiont on Polyblastia albida Arnold (Swinscow in Lichenologist 3: 418. 1967); another, G. jamesii Swinscow (l.c.: 420), was reassigned to Swinscowia S.H. Jiang, Lücking & Sérus. (Hongsanan & al. in Fungal Diversity 10: 139. 2020); and the third, G. xylophila Vězda (in Folia Geobot. Phytotax. 5: 312. 1970), is still known only by the type specimen. For a long time, the type of ascomata has been one of the main characteristics to delimit higher taxa in Ascomycetes. The ascomata of Geisleria are enclosed, perithecium-like with a narrow pore, and therefore G. sychnogonioides has been referred to pyrenocarpous families such as Verrucariaceae in Eurotiomycetes (Stizenberger in Ber. Thätigk. St. Gallischen Naturwiss. Ges. 22: 502. 1882) or Strigulaceae in Dothideomycetes (Harris, Taxon. Revis. Arthopyrenia [Ph.D. thesis, Michigan State University, U.S.A.]: 145. 1975; Roux & Sérusiaux in Biblioth. Lichenol. 90: 89–90. 2004). The relationships of Geisleria with other lichenized genera remained disputable until Aptroot & al. (in Lichenologist 46: 115–128. 2014) showed that Geisleria is sister to the type of the generic name Absconditella, forming a highly supported clade within Stictidaceae. Due to the small sample size, the authors (Aptroot & al., l.c.) only discussed the need for taxonomic re-arrangements but did not perform them. The most recent study on the lichenized genus Absconditella with more species and specimens included (Suija & Van den Boom in Mycol. Progr., in press) confirmed Aptroot & al.'s results as Geisleria was nested within Absconditella, forming a well-supported monophyletic clade. In contrast to Geisleria, the ascomata of Absconditella are cup-shaped with an exposed spore-bearing layer (apothecia). Aptroot & al. (l.c.) examined the type material of G. sychnogonioides and revealed that the ascomata of this species are still typical apothecia but the disc is only narrowly exposed, leaving the impression of enclosed fruit-bodies. The microscopical examination of additional materials by Suija & Van den Boom (l.c.) confirmed their statement. Following the principle of priority (Art. 11.3), we should adopt the earlier generic name Geisleria over Absconditella. However, the recognition and application of the older name would necessitate the introduction of 15 new combinations. Therefore, we propose to conserve the more widely used name Absconditella against Geisleria. AS, https://orcid.org/0000-0003-3784-9414 PvdB, https://orcid.org//0000-0002-1929-2088