''Caloplaca'' is a

lichen A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...

genus comprising a number of distinct species. Members of the genus are commonly called firedot lichen, jewel lichen.Field Guide to California Lichens, Stephen Sharnoff, Yale University Press, 2014, gold lichens, "orange lichens",USDA Natural Resources Conservation Service Name Search
/ref> but they are not always orange, as in the case of '' C. albovariegata''.Plants Profile for Caloplaca (orange lichen), USDA
/ref> The distribution of this lichen genus is worldwide, extending from Antarctica to the high Arctic. It includes a portion of northern North America and the Russian High Arctic. There are about thirty species of ''Caloplaca'' in the flora of the British Isles. A new species of ''Caloplaca'', '' C. obamae'', the first species to be named in honor of

Barack Obama Barack Hussein Obama II (born August 4, 1961) is an American politician who was the 44th president of the United States from 2009 to 2017. A member of the Democratic Party, he was the first African American president in American history. O ...

, was discovered in 2007 on Santa Rosa Island in

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

and published in March 2009.

Taxonomy

''Caloplaca'' was circumscribed in 1860 by Theodor Magnus Fries. Until relatively recently, ''Caloplaca'' was one of the largest genera of lichen-forming fungi, with more than 500 species. Since the advent of

molecular phylogenetics Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

, the formerly

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

genus has been split into more than 30 smaller,

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

genera after many publications by Ukrainian lichenologist Sergey Kondratyuk and colleagues. Modern taxonomic studies have significantly narrowed the definition of ''Caloplaca'', with many species now placed in other genera. The genus shows close relationships to '' Leproplaca'' and '' Variospora'', with many species growing on tree bark.

Description

''Caloplaca'' is a genus of

crustose lichen Crustose lichens are lichens that form a crust which strongly adheres to the Substrate (biology), substrate (soil, rock, tree bark, etc.), making separation from the substrate impossible without destruction. The basic structure of crustose lichen ...

s characterised by their grey to white thallus (main body) and distinctive yellow to orange fruiting bodies (

apothecia An ascocarp, or ascoma (: ascomata), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. As ...

). Unlike some related genera, the thallus lacks anthraquinone pigments but contains pigment, which turns violet when tested with

potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which utili ...

solution (the K spot test). The thallus structure includes a protective outer layer () made of rounded cells. Some species produce reproductive structures called soredia, or isidia. Like most lichens, ''Caloplaca'' contains a green algal partner () from the genus '' Trebouxia''. The apothecia feature a persistent rim () matching the thallus colour, whilst the central (which features the

hymenium The hymenium is the tissue layer on the hymenophore of a fungal fruiting body where the cells develop into basidia or asci, which produce spores. In some species all of the cells of the hymenium develop into basidia or asci, while in oth ...

–the fertile, spore-bearing surface) displays vibrant yellow to orange hues. Internally, the apothecia contain colourless layers and thread-like structures ( paraphyses) that may branch and have enlarged tips. The spore-producing sacs ( asci) each contain eight colourless, elliptical ascospores divided into two compartments by a

septum In biology, a septum (Latin language, Latin for ''something that encloses''; septa) is a wall, dividing a Body cavity, cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Hum ...

. The genus is distinguished by its chemistry, particularly the presence of parietin (the main secondary metabolite) and smaller amounts of related substances. These anthraquinone compounds occur only in the apothecia, not the thallus.

List of species

List of ''Caloplaca'' species

Gallery

Image:Caloplaca sideritis-1.jpg, '' Caloplaca sideritis''

References

{{Taxonbar, from=Q146253 * Lichen genera Teloschistales genera Taxa named by Theodor Magnus Fries Taxa described in 1860