''Cladonia krogiana'' is a species of fruticose lichen in the family Cladoniaceae, described to science in 2002. This lichen is characterised by its greyish-green to medium-brown (scaly) , forming cushions up to wide, with distinctive chemical components including

barbatic acid Barbatic acid is an organic compound that is made by some lichens. It is in the structural class known as depsides. It is particularly common in the genera '' Usnea'' (the beard lichens) and '' Cladonia''. History The compound was first isolat ...

and the rare xanthone compound chlorovinetorin. Originally discovered in southeastern Norway, ''C. krogiana'' has since been found in the Czech Republic and New Brunswick, Canada, typically growing on sun-exposed siliceous rock in periodically wet, open areas near forests and water bodies.

Taxonomy

Described as a new species in 2002 by Bjørn Petter Lofall and Einar Timdal, ''Cladonia krogiana'' was first identified from specimens collected by the authors near the southwestern side of Lake Franesjaen in Østfold, Norway. The

species epithet Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany) A botanical name ...

honours Hildur Krog for her contributions to lichen taxonomy. Molecular phylogenetics studies show that it is closely related to ''

Cladonia robbinsii ''Cladonia'' is a genus of moss-like lichens in the family Cladoniaceae. They are the primary food source for reindeer/caribou. ''Cladonia'' species are of economic importance to reindeer-herders, such as the Sami in Scandinavia or the N ...

'', which is endemic to the Americas.

Description

The of ''Cladonia krogiana'' is (scale-like), persistent, and forms cushions up to wide. The are ascending, up to 8 mm long and 4 mm wide, with to deeply incised edges. They are greyish green to medium-brown on the upper side and white to brownish at the base on the underside. The apothecia (fruiting bodies) are immature and brown, and the species lacks podetia.

Similar species

Although ''Cladonia krogiana'' is closely related to and can be mistaken for a few other species, it is differentiated by its unique chemical profile and certain physical traits. For example, ''

Cladonia strepsilis ''Cladonia strepsilis'' or the olive cup lichen is a species of cup lichen in the family Cladoniaceae. In Iceland, where it is only found in a few locations in the Eastern Region, it is red listed as endangered An endangered species is a ...

'' and ''

'' both contain barbatic acid like ''Cladonia krogiana''. In ''C. strepsilis'', the barbatic acid is present only in the podetia, not in the primary squamules, which instead contain other acids such as baeomycesic acid, squamatic acid, and

strepsilin Strepsilin is a chemical found in Lichen, lichens. It produces an emerald green colour in the C test. It is a dibenzofuran dimer, with hydroxyl, hydroxy, ketone, oxy and methyl side groups. It is named after ''Cladonia strepsilis''. Strepsilin was ...

. This species also features greener, larger, and more (spotted) primary squamules. ''C. robbinsii'' differs from ''C. krogiana'' by having paler yellow, often more } primary squamules containing both barbatic and usnic acids. ''Cladonia polycarpoides'' shares similar a thallus structure with ''C. krogiana'' but is chemically distinct. It is found within the ''C. subcariosa'' group and contains norstictic acid and homoheveadride, contrasting significantly with the depside and xanthone content of ''C. krogiana''. The two species might be distinguished in the field by their spot test reactions: ''C. krogiana'' is negative in all standard chemical tests (PD, K, C, KC, UV), whereas ''C. polycarpoides'' may show positive reactions. Other European ''Cladonia'' species that might be confused with ''Cladonia krogiana'' include '' C. cervicomis'', '' C. callosa'', '' C. firma'', '' C. macrophyllodes'', '' C. subcervicornis'', and '' C. symphycarpia''. These species generally differ in their chemical reactions to PD tests and other specific secondary metabolites they contain, which are not found in ''C. krogiana''. For example, ''C. callosa'' contains grayanic acid and is also a member of the section Helopodium, like ''C. polycarpoides''. The distinctive combination of morphological and chemical characteristics in ''Cladonia krogiana'', particularly the presence of chlorovinetorin and its specific reaction patterns, help in distinguishing it from these similar species.

Chemistry

''Cladonia krogiana'' contains

and chlorovinetorin as major secondary metabolites ( lichen products). It is significant for the presence of the rare xanthone chlorovinetorin, previously reported in only a few other lichen species, and the depside barbatic acid, common in many ''Cladonia'' species but presented in a unique chemical context here.

Distribution and habitat

Known originally from several localities within southeast Norway, ''Cladonia krogiana'' grows on exposed siliceous rock like gneiss and

amphibolite Amphibolite () is a metamorphic rock that contains amphibole, especially hornblende and actinolite, as well as plagioclase feldspar, but with little or no quartz. It is typically dark-colored and dense, with a weakly foliated or schistose (flaky ...

, often in locations that are periodically wetted by trickling water or spring floods. It typically inhabits open, exposed sites on the borders of

conifer Conifers are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single ...

or mixed forests near lakes or rivers. It has also been reported from the Czech Republic, where it was found on open semi-native pine forest on ultramafic rock in the Ransko National Nature Reserve; this is both a geographically and ecologically outlying occurrence for this lichen. The first report of its occurrence in North America was reported in 2021, after it was found in two localities in New Brunswick. This lichen primarily colonises thin soil covers or mosses in its natural habitats, indicating a preference for substrates that provide a stable microclimate and sufficient moisture retention.

References