Arizona Gray Squirrel vs Concentric Boulder Lichen

Sciurus arizonensis compared with Porpidia crustulata

Key Differences

• Arizona Gray Squirrel is Data Deficient while Concentric Boulder Lichen is Vulnerable.

Taxonomic Classification

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

Conservation Status

Arizona Gray Squirrel

DD — Data Deficient

Concentric Boulder Lichen

VU — Vulnerable

Physical Characteristics

Attribute	Arizona Gray Squirrel	Concentric Boulder Lichen
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Arizona Gray Squirrel

Habitat

Typically found in diverse terrestrial and aquatic ecosystems.

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.

Arizona Gray Squirrel

The Arizona Gray Squirrel, Sciurus arizonensis, is a species. Its conservation status is listed as Data Deficient, meaning insufficient information exists to assess its risk of extinction. Typically found in diverse terrestrial and aquatic ecosystems.

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.