Schaereria

Genus Schaereria was circumscribed by German lichenologist Gustav Wilhelm Körber in 1855, with Schaereria lugubris assigned as the type, and at the time, only species.[3] According to Hertel and Zürn, it is clear that he was referring to Schaereria cinereorufa (Schaer.) Th.Fr., but he mistakenly believed he had Ropalospora lugubris (formerly Lecidea lugubris) on hand. For this reason, Körber's name is not available for the genus.[4] The genus was accepted a few years later by Theodor Magnus Fries, who used it in his work on arctic, European, and Greenlandic lichens.[5] It subsequently fell into disuse fore more than a century as William Nylander placed it in synonymy with Lecidea.[6] Josef Poelt and Antonín Vězda resurrected the genus in 1977, and included S. cinereorufa.[7] The genus name Schaereria honours Swiss pastor and lichenologist Ludwig Emanuel Schaerer.[8]

In 1989, a proposal was put forth to conserve the name Schaereria (as defined by Theodor Magnus Fries in 1874) for a group of species with S. cinereorufa as the type species, instead of using Schaereria as defined by Körber. The reason for this proposal is that S. cinereorufa is a well-known species under the name Schaereria, while Körber applied the name S. lugubris to a different species that should have been named S. cinereorufa. By conserving the name Schaereria as suggested, it avoids the need to create a new name for the same group of lichens and prevents confusion with another genus called Ropalospora. By accepting this proposal, both Ropalospora and Schaereria could continue to be used with their current meanings, avoiding any unnecessary changes.[9] In the subsequent recommendations of the Committee for Fungi and Lichens, they agreed that it was desirable to conserve the genus with one of the original specimens used by the author, noting that this specimen was erroneously labelled Schaereria lugubris, but clearly belongs to S. cinereorufa.[10]

Schaereria is one of several dozen genera whose species were previously included in the large genus Lecidea.[11] However, Lecidea has a different ascus structure than Schaereria. The family Schaereriaceae was first proposed by French lichenologist Maurice Choisy in 1949, but he did not publish the name validly.[12] Josef Hafellner published Schaereriaceae validly in 1984.[13]

Hafellner noted some similarities in the characteristics of the hymenium between the Schaereriaceae and the Pezizales,[13] and the family was included there in the 1985 version of the Outline of the Ascomycota.[14] This classification was later shown to be inappropriate as the Schaereriaceae do not have operculate asci—a characteristic of the Pezizales. After this the family was associated with either the Teloschistineae (a suborder of the Teloschistales), the Agyriineae (a suborder of the Lecanorales),[6] or placed in the order Sarrameanales.[15] In 2018, H. Thorsten Lumbsch and Steven Leavitt proposed the new order Schaereriales to contain the family, segregating the order Schaereriales from Sarrameanales. They considered the Schaereriales to have "unresolved relationships" in the parent taxon, Ostropomycetidae. In their analysis, which used a "temporal" method to group together comparable ordinal and family ranks, Schaereriales has a sister group relationship with the order Sarrameanales. Both Schaereriales and Sarrameanales form a clade that is sister to the Baeomycetales.[16][17] In a critical review of the temporal method for lichen classification, Robert Lücking found flaws in their analysis and rejected the proposed split, instead retaining both Sarrameanaceae and Schaereriaceae in the Sarrameanales.[18]

Several characteristics unite taxa in the order Schaereriales. These include: a thallus that is crustose to squamulose; a trebouxioid photobiont partner (spherical unicellular green algae); ascomata being lecideine (having an apothecium which lacks algae and lacks an amphithecium); apothecia that are hemiangiocarpous (meaning they open before the spores are mature); and a cup-shaped excipulum. Microscopic characteristics of the Schaereriales include asci of the Schaereria-type (lacking a tholus–the thickened inner part of an ascus tip), and ascospores that are hyaline, thin-walled, and one-celled (i.e., lacking septa).[16] There are eight spores per ascus. The hamathecium contains non-amyloid, non-gelatinous, unbranched paraphyses.[15] The secondary chemistry of this group includes depsides and unknown compounds.[15] Schaereria cinereorufa produces a green- to turquoise-coloured insoluble lichen pigment known as Cinereorufa-green.[19]

The anatomy and development of several Schaereria species have been studied in some detail. The genus displays a varied morphology, encompassing both crustose and squamulose lichens. For instance, Schaereria cinereorufa is characterised by a squamulose to bullate thallus, often found on siliceous rocks, with sessile or marginally located apothecia. In contrast, S. corticola exhibits a sparsely developed, endo- to episubstral thallus with soredia and sessile apothecia. Schaereria fuscocinerea, somewhat intermediate, features an areolate thallus on siliceous rocks, and its fruiting bodies are either immersed in or between areolae}.[6]

The anatomy within the genus is more consistent. In S. cinereorufa and S. fuscocinerea, the thallus is covered by an epinecral layer, and no distinct cortex is formed. However, the upper parts of the hyphae in the thallus are pigmented brownish. In contrast, S. corticola lacks a distinct upper layer, primarily consisting of soredia.[6]

The development of Schaereria ascomata is somewhat variable depending on species. In S. cinereorufa, the ascomatal primordium begins as groups of ascogonia forming a more or less spherical cluster, followed by coiled ascogonia with trichogynes. The primordium eventually rises to the thallus's upper surface, with the upper part forming the hymenium. In S. corticola, spherical primordia with ascogonia are observed, becoming pigmented and forming the cup-shaped excipulum. True paraphyses replace the paraphysoidal network in the hamathecium. In S. fuscocinerea, ascogonia with trichogynes appear in the algal layer, with subsequent growth of paraphysoids, followed by the differentiation of ascogenous hyphae and true paraphyses.[6]

Collectively, the genus has a cosmopolitan distribution.[15] The majority of Schaereria species inhabit cold to cool climates within the Northern Hemisphere. However, S. fuscocinerea is an exception, as it can be found in both polar regions. Additionally, S. xerophila thrives in the lowland regions of Queensland. Schaereria species are typically found growing on rocky surfaces composed of siliceous materials. However, S. corticola adopts an epiphytic lifestyle, while S. parasemella has a lichenicolous (lichen-dwelling) habit.[20]

Some lichenicolous (lichen-dwelling) fungi and lichens have been recorded growing on Schaereria species. These include Endococcus perpusillus, Buellia miriquidica, Buellia uberior, and Halecania parasitica (the last three on Schaereria fuscocinerea).[21] A Sclerococcum species in the S. australe-S. saxatile group has been reported infesting Schaereria bullata.[20]

As of September 2023, Species Fungorum (in the Catalogue of Life) accepts 11 species of Schaereria.[22]

• Schaereria albomarginata Øvstedal (2009)[23]
• Schaereria argentina Gyeln. (1934)[24]
• Schaereria australis Kantvilas (2023)[25] – Australia
• Schaereria brunnea Björk, T.Sprib. & T.B.Wheeler (2009)[26] – Canada
• Schaereria bullata Kantvilas (1999)[20] – Tasmania
• Schaereria cinereorufa (Schaer.) Th.Fr. (1861) – Northern Hemisphere
• Schaereria corticola Muhr & Tønsberg (1992)[27] – temperate Northern Hemisphere
• Schaereria dolodes (Nyl.) Schmull & T.Sprib. (2005)[28] – western North America; Tasmania
• Schaereria fabispora Hertel & Zürn (1986)[4] – Norway
• Schaereria fuscocinerea (Nyl.) Clauzade & Cl.Roux (1985) – cosmopolitan distribution
• Schaereria gresinonis (B.de Lesd.) Gyeln. (1937)
• Schaereria parasemella (Nyl.) Lumbsch (1997)[29] – Finland
• Schaereria porpidioides Fryday & Common (2001)[30] – Falkland Islands
• Schaereria serenior (Vain.) Vitik. (2004) – Fennoscandia
• Schaereria xerophila Rambold & H.Mayrhofer (1989)[31] – Australia