Ramalina calicaris is a species of fruticose, bark-dwelling lichen-forming fungus in the family Ramalinaceae. The lichen forms tufted to hanging, greenish-grey shrubby growth anchored by a holdfast at the base, with branches that are often distinctly channelled and strap-shaped, typically 2–3 mm wide and reaching 15–20 cm in length. Its reproductive structures are frequently produced, appearing as pale pink-ochre discs borne at the tips or margins of the branches, often on bends of angled branches with short spur-like projections. The species grows primarily on the branches and twigs of trees and shrubs with nutrient-rich bark, particularly in coastal settings and humid forests. Chemically, the cortex contains usnic acid, while the medulla may contain compounds of the sekikaic acid complex or lack additional substances. The species occurs across Europe (where it is most frequent in western districts), North Africa, Macaronesia, and parts of Asia including China, India, and Thailand. The taxonomy of R. calicaris has been complicated by historical confusion over which specimens should be considered the original type material, leading to ongoing nomenclatural debates about the proper application of the name. Linnaeus's original Lichen calicaris encompassed both rock-dwelling and bark-dwelling material, but subsequent lectotypification fixed the name to a rock-dwelling specimen corresponding to Ramalina siliquosa, conflicting with long-established usage for the bark-dwelling species. Several taxa historically described as infraspecific forms of R. calicaris are now recognised as distinct species, including Ramalina farinacea, Ramalina fastigiata, and Ramalina fraxinea. The species is commonly fertile and has been shown (in at least one Asian variety) to be sensitive to nitrogen pollution.
Taxonomy The name Ramalina calicaris is based on the basionym Lichen calicaris, attributed to Carl Linnaeus in 1753. During this era, the term Lichen was used as a broad generic descriptor for nearly all known lichenized fungi, reflecting an early stage of biological classification where the symbiotic nature of the organism was not yet understood. In the protologue Linnaeus characterized it as an erect, narrow, branching lichen with a pitted (lacunose), convex surface and pointed (mucronate) tips, and gave its habitat as "in Europe, on trees and rocks". The species was reclassified in Ramalina by Johann Christoph Röhling in 1813, a genus erected by Erik Acharius in 1810. Some secondary and regional treatments instead cite the author as Elias Magnus Fries (1824), reflecting a later combination that remains in circulation in parts of the literature and regional databases. In a 1913 revision of North American Ramalina, Reginald Heber Howe, Jr. reviewed the Linnean Society herbarium sheets associated with Lichen calicaris and reported that, among the specimens he regarded as original material, the better-preserved thalli correspond to the rock-dwelling taxon then treated as Ramalina scopulorum. He therefore argued that Linnaeus's brief diagnosis was more consistent with that concept than with Fries's later f. canaliculata, illustrating that uncertainty over how the epithet calicaris should be applied predates modern typification and conservation work. In a subsequent instalment of his North American revision, Howe (1914) treated the canaliculate taxon that had often circulated as R. calicaris in older American usage under the name Ramalina canaliculata (Fr.) Herre, tying it to Fries's R. calicaris "canaliculata" concept and summarizing its diagnostic features (including canaliculate laciniae and typically subterminal, spurred apothecia).
Howe also commented on the older "catch-all" use of R. calicaris in North American literature for intergrading forms, and reviewed Vainio's 1888 argument that Linnaeus's epithet calicaris should be applied to Fries's canaliculata on the basis of specimens in the Linnean herbarium. He rejected that evidentiary basis, arguing that the specimens in question were not Linnean types (and were probably added after Linnaeus's death) and that Linnaeus's original description is not diagnostic for the canaliculate taxon. Sheard and James (1976), in a typification study of the Ramalina siliquosa species aggregate, re-examined the lectotype of Lichen calicaris (LINN 1273.115; lectotype designated by Howe) and reported that it belongs to the R. siliquosa complex and contains protocetraric acid. They also noted that other Linnean material previously treated as "type" for L. calicaris is in poor condition and does not correspond to the corticolous species that most lichenologists had long been calling Ramalina calicaris. A nomenclatural review of Linnaean lichen names reported that Linnaeus's original concept of Lichen calicaris encompassed both saxicolous (rock-dwelling) and corticolous (bark-dwelling) material. It concluded that Howe's lectotypification nevertheless fixes the name to a saxicolous specimen corresponding to Ramalina siliquosa and is "formally correct" under the Code; however, the authors described this outcome as "most unfortunate" because it conflicts with long-established usage of Ramalina calicaris for a corticolous species. To avoid a disruptive name change, the same review indicated that conservation of the name would be proposed so that Lichen calicaris could continue to be used in its traditional sense for the bark-dwelling species. In a separate paper, Jørgensen, James and Jarvis formally proposed conserving Lichen calicaris with a conserved type (from Dillenius's herbarium) that matches the corticolous species, so that Ramalina calicaris would continue in its long-established sense. The Nomenclature Committee for Fungi later recommended acceptance of the Linnaean-name proposals, including conservation of Lichen calicaris, supporting continued use of the name for the bark-dwelling species. In discussing confusion among fertile, corticolous Ramalina in European herbaria, Groner and LaGreca (1997) traced long-running misapplications to imprecise original and subsequent diagnoses that did not cleanly delimit similar shrubby species, meaning that morphology alone often proved insufficient for routine identification in collections.
Former infraspecific taxa Several taxa historically described as infraspecific types of Ramalina calicaris (forms, varieties, or subspecies) are now recognized as distinct species in Ramalina. These include:
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