Concentric Boulder Lichen vs Japanese Squirrel

Porpidia crustulata compared with Sciurus lis

Key Differences

Concentric Boulder Lichen is Vulnerable while Japanese Squirrel is Least Concern.

Taxonomic Classification

Rank	Concentric Boulder Lichen	Japanese Squirrel
Kingdom	Fungi (Fungi)	Animalia (Animals)
Phylum	Ascomycota (Sac Fungi)	Chordata (Chordates)
Class	Lecanoromycetes (Lecanoromycetes)	Mammalia (Mammals)
Order	Lecideales (Lecideales)	Rodentia (Rodents)
Family	Lecideaceae	Sciuridae (Squirrels)
Genus	Porpidia	Sciurus (Tree Squirrels)
Species	Porpidia crustulata	Sciurus lis

Conservation Status

Concentric Boulder Lichen

VU — Vulnerable

Japanese Squirrel

LC — Least Concern

Physical Characteristics

Attribute	Concentric Boulder Lichen	Japanese Squirrel
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Concentric Boulder Lichen

Habitat

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

Range

Distributed across Denmark, Norway, Portugal, Sweden, and United States. Currently classified as Vulnerable on the IUCN Red List, this species faces significant conservation challenges across its range.

Japanese Squirrel

Habitat

Typically found in diverse terrestrial and aquatic ecosystems.

Range

Distributed across Belgium, France, Netherlands, and United Kingdom.

Concentric Boulder Lichen

<em>Porpidia crustulata</em>, commonly known as the Concentric Boulder Lichen, is a crustose lichen in the family Porpidiaceae formed through a symbiotic relationship between a fungal partner (mycobiont) and photosynthetic green algae (photobiont). Like all crustose lichens, it grows tightly appressed to its substrate—typically siliceous or acidic rock surfaces including boulders, cliff faces, and pebbles in open, well-lit habitats—forming thin, grayish to pale thalli marked by scattered black apothecia (reproductive discs). <em>Porpidia crustulata</em> derives nutrition entirely through photosynthesis conducted by its algal partner, requiring no external organic food source. The species has been documented in Denmark, Norway, Portugal, Sweden, and the United States, suggesting a broad boreal to temperate distribution across the Northern Hemisphere. It is currently classified as Vulnerable by the IUCN, indicating significant conservation concern, likely linked to threats including air pollution, acidification, quarrying of rocky habitats, and changes in land use that reduce the availability of suitable substrates. Crustose lichens are typically slow-growing, long-lived organisms with limited capacity for rapid range shifts in response to environmental change. Biological traits such as individual lifespan, growth rates, and reproductive output remain poorly documented at the population level.