Common Wall Cress vs Concentric Boulder Lichen

Arabidopsis thaliana compared with Porpidia crustulata

Key Differences

• Common Wall Cress is Least Concern while Concentric Boulder Lichen is Vulnerable.

Taxonomic Classification

Rank	Common Wall Cress	Concentric Boulder Lichen
Kingdom	Plantae (Plants)	Fungi (Fungi)
Phylum	Magnoliophyta (Flowering Plants)	Ascomycota (Sac Fungi)
Class	Magnoliopsida (Dicots)	Lecanoromycetes (Lecanoromycetes)
Order	Brassicales (Brassicales)	Lecideales (Lecideales)
Family	Brassicaceae	Lecideaceae
Genus	Arabidopsis	Porpidia
Species	Arabidopsis thaliana	Porpidia crustulata

Conservation Status

Common Wall Cress

LC — Least Concern

Concentric Boulder Lichen

VU — Vulnerable

Physical Characteristics

Attribute	Common Wall Cress	Concentric Boulder Lichen
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Common Wall Cress

Habitat

Typically found in diverse terrestrial habitats from tropical forests to temperate regions.

Range

Widely distributed across Africa (South Africa), Asia (Japan, Taiwan), Europe (11 countries), North America (Canada, United States), Oceania and the Pacific (Australia), and South America (Brazil, Chile).

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.

Common Wall Cress

<em>Arabidopsis thaliana</em>, commonly known as common wall cress or thale cress, is a small annual flowering plant in the family Brassicaceae native to Eurasia and Africa, and now naturalized in North America, Australia, and other temperate regions worldwide. The species has become one of the most important model organisms in plant biology and genetics, owing to its small genome size, short generation time of approximately six weeks, prolific seed production, and ease of laboratory cultivation. <em>Arabidopsis thaliana</em> was the first plant to have its complete genome sequenced, in 2000, revolutionizing our understanding of plant molecular biology, development, and physiology. In nature, it typically grows in rocky outcrops, disturbed sandy soils, walls, roadsides, and waste ground, tolerating poor nutrient conditions and a wide range of climates. The plant produces a basal rosette of small ovate leaves, followed by an erect flowering stem bearing tiny white four-petaled flowers and slender silique seed pods. Despite its modest appearance, <em>Arabidopsis thaliana</em> has facilitated thousands of scientific discoveries in plant genetics, epigenetics, and stress responses. The species is currently assessed as Least Concern by the IUCN. Biological traits such as average lifespan, plant height up to 30 centimeters, and seed output are well-characterized in laboratory settings.

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.

Shared Countries

Both species can be found in 5 countries:

🇩🇰 Denmark 🇳🇴 Norway 🇵🇹 Portugal 🇸🇪 Sweden 🇺🇸 United States