Lecanora albellula is a species of crustose lichen in the family Lecanoraceae. It grows tightly attached to the bark and wood of trees in both coniferous and mixed forests. First described in 1866 by the Finnish lichenologist William Nylander from material collected in Russian Lapland, it is widely distributed across Asia, Europe, and North America. The species is easily recognised by its pale, finely granular thallus—which can appear somewhat wart-like—and its small, round, light brick-coloured apothecia. Its name, referring to its whitish appearance, is based on traditional morphological observations used to distinguish it from similar species. Research has refined the understanding of L. albellula through both modern genetic studies and detailed chemical analyses. These studies have clarified its placement within a well-defined clade of related lichens and revealed that some North American specimens previously identified as this species actually represent a closely related taxon, provisionally known as "Lecanora sp. D". Lecanora albellula produces characteristic secondary metabolites, notably isousnic acid, which, together with its distinctive anatomical and reproductive features, aids in distinguishing it from its congeners. Its occurrence on various tree barks and wood, particularly in temperate to subalpine regions, highlights its specific ecological requirements and the ongoing need for careful taxonomic verification.
Taxonomy Lecanora albellula was first described by the Finnish lichenologist William Nylander in 1866, based on specimens collected near Kantalahti in Russian Lapland. Nylander's original description highlighted its whitish, minutely granular thallus over a thin greyish-black hypothallus, and its small (0.5 mm wide), pale brick-coloured fruiting bodies (apothecia). He initially placed it in the genus Lecidea, though he noted it might better belong in Lecanora due to the structure of its young apothecia, which showed a thalline margin characteristic of Lecanora species. This taxonomic insight proved prescient, as the species is now firmly established within the genus Lecanora. The specific epithet albellula refers to its whitish appearance. The species has a complex taxonomic history, particularly regarding its relationship with Lecanora piniperda Körb., a name that was long used for this species but was later found to be illegitimate under botanical nomenclature rules. Molecular phylogenetic studies have shown that L. albellula belongs to a "core clade" within the broader Lecanora saligna group, closely related to L. subsaligna and L. saligna. This core clade is characterised by the production of isousnic acid as a major metabolite and the presence of crescent-shaped macroconidia. Molecular evidence indicates that North American specimens previously identified as L. albellula actually represent a different species, provisionally named "Lecanora sp. D". The species belongs to the diverse lichen genus Lecanora and is part of a group characterised by a corticate amphithecium (the outer layer of the fruiting body). Within the broader Lecanora genus, L. albellula belongs to a subgroup that contains both usnic and isousnic acids, distinguishing it from the Lecanora subfusca group that contains different chemical compounds. This chemical composition, along with anatomical features, helps define its taxonomic position. Morphologically and anatomically, L. albellula shows close relationships to several other Lecanora species, particularly L. saligna and L. subintricata. However, it can be distinguished from these relatives by its specific combination of characteristics, including spore size, hymenium height, and chemical composition. The species demonstrates some anatomical variability, which led to historical confusion about its taxonomic placement. For instance, the variable structure of its apothecial margin prompted some researchers, like Józef Motyka, to propose placing it in a separate genus (Lecidorina), though this classification was not widely accepted. The traditional Lecanora saligna group, which includes L. albellula, has been found to be paraphyletic based on molecular evidence, with the L. varia group nested within it. While the exact phylogenetic relationships within this complex remain incompletely resolved, the presence of specific morphological and chemical characters helps define natural groupings within the broader assemblage. Recent studies have proposed segregating L. albellula into Lecanoropsis (a genus proposed by Maurice Choisy in 1949, with Lecanoropsis saligna as the type species), reflecting its distinct morphological and reproductive features. Additionally, L. albellula var. macroconidiata is distinguished by larger, 1–3-septate macroconidia measuring 12.5–14 by 1.8–2.3 μm, based on a historical collection from Middlesex. The German-language common name for the species, Kiefern-Kuchenflechte, translates to "pine cake lichen".
Description
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