Concentric Boulder Lichen vs Polar bear

Porpidia crustulata compared with Ursus maritimus

Taxonomic Classification

Rank	Concentric Boulder Lichen	Polar bear
Kingdom	Fungi (真菌界)	Animalia (动物界)
Phylum	Ascomycota (子囊菌门)	Chordata (脊索动物门)
Class	Lecanoromycetes (茶漬綱)	Mammalia (哺乳動物)
Order	Lecideales (网衣目)	Carnivora (食肉目)
Family	Lecideaceae	Ursidae (Bears)
Genus	Porpidia	Ursus (Bears)
Species	Porpidia crustulata	Ursus maritimus

Conservation Status

Concentric Boulder Lichen

VU — Vulnerable

Polar bear

VU — Vulnerable

Population: ~26.0K

Trend: Decreasing ↓

Physical Characteristics

Attribute	Concentric Boulder Lichen	Polar bear
Diet	—	Carnivore
Average Lifespan	—	25 years
Average Length	—	2.4 m
Average Weight	—	450.0 kg

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.

Polar bear

Habitat

Found across multiple habitat types including temperate broadleaf and mixed forests, temperate coniferous forests, and boreal forests and taiga, among 4 distinct biome types within the Palearctic biogeographic realm. Populations are also found in montane and highland environments at higher elevations.

Range

Found in Norway. Currently classified as Vulnerable on the IUCN Red List, this species faces significant conservation challenges across its range.

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.