Kuettlingeria soralifera

Kuettlingeria soralifera is a saxicolous (rock-dwelling), crustose lichen species in the family Teloschistaceae, first described in 2006. It is similar to Kuettlingeria xerica but distinguished by the presence of soredia on its thallus.

Taxonomy
Caloplaca soralifera was described by the lichenologists Jan Vondrák and Pavel Hrouzek in 2006. Its species name, soralifera, refers to its distinct feature of producing soredia, which are grey or grey-violet in colour. The type specimen was collected near a small pond in Křivoklát, (Rakovník District, Czech Republic), at an altitude of 348 m; there, it was found growing on the horizontal side of a concrete wall. Sergey Kondratyuk proposed that the taxon should be transferred to the genus Pyrenodesmia in 2020. Frolov, Vondrák and Arup transferred it to the genus Kuettlingeria in 2020.

Description
This lichen has a crustose, to somewhat  thallus, typically dark to pale grey, and often appears whitish due to. The are flat to convex, measuring 0.2 to 0.8 mm in diameter. It produces dark grey to violet-grey soralia at the margins of the areoles and, which can sometimes cover the entire thallus surface. The of the thallus is greyish to violet-grey, and the  comprises a mixture of algal and fungal cells. The soredia and cortex react positively to various chemical spot tests, indicating the presence of the pigment.

Apothecia, when present, are small, with orange to brown and a yellow to orange. The hymenium is hyaline and contains oil drops. Asci are typically 50 to 80 μm in size, containing, hyaline spores.

Chemistry
Unlike most members of the Teloschistaceae, Caloplaca soralifera lacks anthraquinone substances in the thallus. Instead, this species contains the unique pigment Sedifolia-grey, which does not dissolve in acetone and is found in both the cortex and the soredia. This pigment gives the soredia their characteristic grey or grey-violet colouration.

In the apothecia of Caloplaca soralifera, the primary chemical compound is parietin, accounting for a significant percentage of its composition. Parietin is a well-known lichen secondary metabolite, typically associated with bright orange or yellow colours in many lichen species. Additionally, trace amounts of other anthraquinones, such as fragilin, emodin, and emodial, are present in varying concentrations. The presence and proportions of these compounds helps distinguish C. soralifera from closely related species.

This species falls into what is known as A, as defined in a previous study by Ulrik Søchting. This classification is based on its chemical profile, particularly the dominance of parietin, which is a clear differentiator from species in chemosyndrome B that typically have other anthraquinones as dominant compounds.

Similar species
Caloplaca soralifera shares similarities with several species the Caloplaca, particularly in terms of apothecium structure. The variability in their chemical compositions, particularly the presence or absence of specific compounds like parietin and anthraquinones, plays a significant role in differentiating them.

Kuettlingeria furax: This species typically produces large lobules on the thallus surface and is delimited by conspicuous marginal lobes. Unlike C. soralifera, K. furax does not produce soredia and is considered a strictly parasitic species on Aspicilia species.

Caloplaca spalatensis: It lacks structures for vegetative dispersal and presents flat areoles. C. spalatensis is found on calcareous bird perching boulders in Mediterranean regions, contrasting with the habitat preference of C. soralifera.

Kuettlingeria xerica: Perhaps the most similar to C. soralifera, K. xerica does not produce soredia. Though morphologically similar, the two species belong to different chemosyndromes, with K. xerica lacking the parietin found in C. soralifera.

Caloplaca chlorina: When sterile, C. soralifera can be confused with C. chlorina. However, C. chlorina usually has a non-pruinose thallus and, when fertile, differs significantly in its lecanorine apothecial margin.

Habitat, distribution, and ecology
Caloplaca soralifera is predominantly found on artificial substrates like asphalt, concrete, and mortar, and occasionally on natural substrates such as calcareous and siliceous rocks. It has been recorded in several European countries, including Austria, Bulgaria, the Czech Republic, Germany, Slovakia, and Romania, growing in exposed horizontal sides of structures. Its recorded elevation range is between 220 and 1450 m.

This species is often associated with other lichens like Caloplaca crenulatella and Lecanora muralis. Its presence has been increasing in certain areas, possibly due to expanding substrate preferences and climatic changes favouring nitrophilous and basiphilous lichens.