Ajuga vs Concentric Boulder Lichen

Ajuga reptans compared with Porpidia crustulata

Key Differences

Ajuga is Endangered while Concentric Boulder Lichen is Vulnerable.

Taxonomic Classification

Rank	Ajuga	Concentric Boulder Lichen
Kingdom	Plantae (Plants)	Fungi (Fungi)
Phylum	Magnoliophyta (Flowering Plants)	Ascomycota (Sac Fungi)
Class	Magnoliopsida (Dicots)	Lecanoromycetes (Lecanoromycetes)
Order	Lamiales (Lamiales)	Lecideales (Lecideales)
Family	Lamiaceae	Lecideaceae
Genus	Ajuga	Porpidia
Species	Ajuga reptans	Porpidia crustulata

Conservation Status

Ajuga

EN — Endangered

Concentric Boulder Lichen

VU — Vulnerable

Physical Characteristics

Attribute	Ajuga	Concentric Boulder Lichen
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Ajuga

Habitat

Found across multiple habitat types including temperate broadleaf and mixed forests, tundra, and tropical and subtropical moist broadleaf forests, among 11 distinct biome types. Populations are also found in montane and highland environments at higher elevations.

Range

Widely distributed across Africa (South Africa), Asia (Japan), Europe (6 countries), North America (Canada, United States), Oceania and the Pacific (Australia, New Zealand), and South America (Brazil, Colombia). Currently classified as Endangered on the IUCN Red List, this species faces significant conservation challenges across its 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.

Ajuga

The Ajuga (Ajuga reptans) is a species in the genus Ajuga. It is currently classified as Endangered on the IUCN Red List. Found across multiple habitat types including temperate broadleaf and mixed forests, tundra, and tropical and subtropical moist broadleaf forests, among 11 distinct biome types. Populations are also found in montane and highland environment.

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.