Chlorine Dust Lichen vs Frosted Comma Lichen

Chrysothrix chlorina compared with Chrysothrix caesia

Key Differences

• Chlorine Dust Lichen is Extinct while Frosted Comma Lichen is Not Evaluated.

Taxonomic Classification

Rank	Chlorine Dust Lichen	Frosted Comma Lichen
Kingdom same	Fungi (Fungi)	Fungi (Fungi)
Phylum same	Ascomycota (Sac Fungi)	Ascomycota (Sac Fungi)
Class same	Arthoniomycetes (Arthoniomycetes)	Arthoniomycetes (Arthoniomycetes)
Order same	Arthoniales (Arthoniales)	Arthoniales (Arthoniales)
Family same	Chrysotrichaceae	Chrysotrichaceae
Genus same	Chrysothrix	Chrysothrix
Species	Chrysothrix chlorina	Chrysothrix caesia

Evolutionary Relationship

Chlorine Dust Lichen and Frosted Comma Lichen share a common ancestor at the Genus level: Chrysothrix.

Conservation Status

Chlorine Dust Lichen

EX — Extinct

Frosted Comma Lichen

NE — Not Evaluated

Physical Characteristics

Attribute	Chlorine Dust Lichen	Frosted Comma Lichen
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Chlorine Dust Lichen

Habitat

Native to Europe and North America and South America, inhabiting ecosystems characteristic of the region.

Range

Widely distributed across Europe (4 countries), North America (United States), and South America (Brazil, Colombia).

Frosted Comma Lichen

Habitat

Native to Europe and North America, inhabiting ecosystems characteristic of the region.

Range

Distributed across Norway, Sweden, and United States.

Chlorine Dust Lichen

The Chlorine Dust Lichen (Chrysothrix chlorina) is a crustose lichen in the family Chrysotrichaceae, historically known from calcareous and siliceous rock surfaces and bark in parts of Europe, including the United Kingdom. It belongs to the genus Chrysothrix, a group of powdery, granular lichens that form bright yellow to greenish-yellow leprose thalli — lacking the organised cortex layers of most lichens — composed largely of granular soredia. Chrysothrix species produce unique secondary metabolites including rhizocarpic acid, which contributes to their intense yellow colouration and may serve as protection against grazing invertebrates. The Chlorine Dust Lichen takes its name from the sharp, bleach-like or chlorine odour emitted when the thallus is moistened — a distinctive diagnostic feature. The IUCN has assessed this species as Extinct in Great Britain, where it was historically recorded from ancient woodland and shaded rock sites but has not been confirmed in recent decades. Its apparent extinction in parts of its former range is attributed primarily to severe air quality degradation during the industrial era, as many crustose lichens are highly sensitive to sulphur dioxide and other atmospheric pollutants. It may persist in small areas of cleaner air, and improved air quality since deindustrialisation offers some hope for natural recolonisation.

Shared Countries

Both species can be found in 3 countries:

🇳🇴 Norway 🇸🇪 Sweden 🇺🇸 United States