Niebla homalea is a species of fruticose lichen that grows on rocks in foggy areas along the Pacific Coast of North America, from Mendocino County, California south to Bahía de San Quintín on the main peninsula of Baja California, with an isolated occurrence further south on vertical rock faces above Punta Camachos, and other occurrences in the Channel Islands and on Guadalupe Island. The epithet homalea, given by Acharius, suggests it was in regard to the branches appearing flattened.
Distinguishing features
Niebla homalea is recognized by the thallus divided into narrow subcylindric, mostly linear shaped branches that have a glossy cortex frequently cracked along transverse ridges and by the branch margins alternating 90° in their orientation at frequent but irregular intervals; the branches are 4–8 cm long, 1–3 mm wide. Apothecia, when present, develop terminally, and are flattened towards base where attached to branch. The key lichen substance is divaricatic acid, with accessory triterpenes and usnic acid. Similar species include Niebla eburnea, distinguished by a glazed (ivory) cortex, often with wrinkles or ripples instead of transverse cracks, and by the branch margins alternating with the cortical ridges more near base and apex; Niebla testudinaria, distinguished by the reticulate ridges between branch margins, and Niebla disrupta that differs by the lichen substance, sekikaic acid. Both N. eburnea and N. testudinaria frequently have irregularly dilated branches, especially above mid region, which helps separate them from N. homalea. Niebla disrupta generally has apothecia, usually more developed below mid region of the thallus, and usually with an extended spine-like branch, whereas in N. homalea, apothecia appear less frequent and mature more near apex of branches, often on a short truncated branch, occasionally with a continuing flattened branch.
Taxonomic history
Niebla homalea, which is classified in the family Ramalinaceae, was originally describedin 1810 by Swedish botanist Erik Acharius as a species of Ramalina based on a specimen collected by Archibald Menzies on rocks around San Francisco. A related species described in 1803 by Acharius, Parmelia ceruchis, was transferred by Acharius to the genus Borrera and has since been recognized in Niebla, following transfer first to Ramalina by Giuseppe De Notaris in 1846
This, however, is only part of a long confusing history as to what defined Ramalina ceruchis (=Vermilacinia ceruchis), which has to be based on a type (biology) specimen, one that was collected also by Menzies, probably on sand in a fog region at Valparaiso Chile, while type material also includes a specimen collected by Joseph Dombey from Lima, Peru. The interpretation of Ramalina ceruchis of South America—over time—was broadened to include morphological variants that grew on rocks, bushes and cactus spines; sometimes classified in other genera such as Evernia, Roccella, and Usnea some recognized as different varieties and species. In 1852 they were all considered just one species that included the North American Ramalina homalea, treated by Jean Camille Montagne under a new genus, Desmazieria, comprising a single species named Desmazieria homalea Although Parmelia ceruchis (Acharius 1803) predates Ramalina homalea (Acharius 1810), the type species for the genus Niebla has to be typified by type of the name (basionym in this case) according to the International Code of Botanical Nomenclature (Art. 7.1, 7.2, and 7.3); thus, the type species in the genus (Niebla) has to be Niebla homalea., it is not Niebla ceruchis<ewd>Sérusiaux, E., P. Van den Boom, and D. Ertz. 2010. A two-gene phylogeny shows the lichen genus Niebla (Lecanorales) is endemic to the New World and does not occur in Macaronesia nor in the Mediterranean basin.